Integrated Pest Management in Mediterranean Greenhouses by CropLife Europe

Integrated Pest Management in mediterranean greenhouses © 2013 of the text: The authors © 2013 of this edition: Cajamar Caja Rural Edited by: Cajamar Caja Rural Plaza Barcelona, 5. 04006 ALMERIA Telephone: (+34) 950 210 386 publicaciones@cajamar.com www.publicacionescajamar.es Translator: Andrew John Mortimer Publishing date: 2014 Cajamar Caja Rural accepts no responsibility for the information and opinions contained in this publication for which the authors bear full responsibility. © All rights reserved. The total or partíal reproduction of this publication is strictly forbidden as is the reprographic or phonic edition of its contents by electronic or mechanical means, especially printing, photocopying, microfilming, offset printing or mimeography without prior authorisation, in writing, from the copyright holders.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Authors Project rationale Jan Rether - Project lead of the Residues Management Project at ECPA Juan Carlos Gázquez Garrido - Cajamar Research Centre ‘Las Palmerillas’

Almeria, an Example of Integrated Pest Management in mediterranean greenhouses Juan Carlos Gázquez Garrido Cajamar Research Centre ‘Las Palmerillas’

Greenhouse structures Juan Carlos López Hernández Greenhouse Technology Area Cajamar Research Centre ‘Las Palmerillas’

Greenhouse covering materials in the Mediterranean Juan Carlos López Hernández Greenhouse Technology Area Cajamar Research Centre ‘Las Palmerillas’

Greenhouse ventilation and cooling J.C. López1; J. Pérez-Parra1, J.I. Montero2, E. Baeza1, A. Antón2 1 Cajamar Research Centre ‘Las Palmerillas’ 2 Institut de Recerca i Tecnologia Agroalimentàries (Institute for Agrifood Research and Technology)

Greenhouse climate control Juan Carlos López Hernández Greenhouse technology Area Cajamar Research Centre ‘Las Palmerillas’

Greenhouse technology & integrated pest management Gázquez, J.C.; López, J.C.; Pérez, C., J.C.; Baeza, E.; Meca, D.; Pérez-Parra, J. Cajamar Research Centre ‘Las Palmerillas’

Soil cultivation: Characteristics, correction and disinfection Antonio José Céspedes López Cajamar Research Centre ‘Las Palmerillas’

The irrigation of greenhouse crops Fernández M.D1; Thompson R.B.2; Bonachela S. 2; Gallardo M. 2; Granados M.R. 2 1 Cajamar Research Centre ‘Las Palmerillas’ 2 Universidad of Almeria

Fertirrigation Juan José Magán Cañadas 1; Mª Dolores Fernández Fernández 1; Thompson R.B.2; Granados M.R.2 1 Cajamar Research Centre ‘Las Palmerillas’ 2 Universidad of Almeria

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management Juan José Magán Cañadas Cajamar Research Centre ‘Las Palmerillas’

Waste, or Products with Other Qualities and Different Uses? Sevilla, A.; Domene, M.A.; Uceda, M.; Buendía, D.; Racero, J.L. Cajamar Research Centre ‘Las Palmerillas’

Optimising the application of phytosanitary products in greenhouses Julián Sanchez- Hermosilla¹, Victor J. Rincón¹, Francisco Páez², Milagros Fernández² ¹ Dept. Engineering. University of Almeria. Campus of International Excellence in Food and Agriculture CeiA3. ² Institute for Agriculture and Fisheries Research and Training (IFAPA- La Mojonera). Junta de Andalucía

Managing resistance to insecticides Pablo Bielza Lino Full-Professor - Department of Plant Production Superior Technical School of Agricultural Engineering - Polytechnic University of Cartagena

Greenhouse pest and disease control: Sublimators Corpus Pérez Martínez Cajamar Research Centre ‘Las Palmerillas’

Biological control in Greenhouses Mónica González Fernández Cajamar Research Centre ‘Las Palmerillas’

Best agricultural practices in the greenhouse: The key to success in integrated pest control management Juan Carlos Gázquez Garrido Cajamar Research Centre ‘Las Palmerillas’

Diseases affecting the main horticultural crops in the greenhouses of Almeria María Antonia Elorrieta Jove Departamento de Fitopatología, LABCOLOR

The integrated pest and disease management of pepper crops Francisco Salvador Sola Nature Choice S.A.T.

The integrated pest and disease management of tomato crops David Erik Meca Abad Cajamar Research Centre ‘Las Palmerillas’

Agrochemical container management Victorino Martínez Puras SIGFITO

Certification & traceability Francisco Guillén Salmerón Proyecta Ingenio S.L.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated Pest Management in mediterranean greenhouses Coordinators Juan Carlos Gázquez Garrido Jose Luis Racero Luque-Racero Cajamar Research Centre ‘Las Palmerillas’ Prologue European society is becoming increasingly demanding regarding the quality of the food it eats. It is also sensitive to everything related with agricultural practices that may affect the environment. Consequently, producers must be able to ensure that their production processes are respectful with both the environment and workers alike while using farming techniques to produce quality food and free of residues that may affect the health of consumers. This is why the responsible and efficient use of phytosanitary products is of the utmost importance to be able to achieve these objectives while reducing their effect on the environment Training is one of the basic supports for the development of intensive greenhouse agriculture. This type of agriculture is very dynamic and has a high degree of professionalism, which is why both technicians and farmers are continuously demanding the latest knowledge. The Cajamar Research Centre ‘Las Palmerillas’ has, since its foundation in 1975, been committed to innovation and subsequent knowledge transfer to the agrifood sector. This training material has been prepared following a process of technology transfer involving researchers, technicians and trainers. The aim is for this book to become a useful and innovative tool for instructors in other Mediterranean areas who want to benefit from the experience of southeastern Spain to implement integrated pest management strategies. This manual is intended to communicate the procedures that have enabled the Integrated Pest Management in greenhouses that is taking place in Spain in general and in Almeria in particular, to become a benchmark for Mediterranean producers. It includes the measures related to the implementation of best practices, the compliance with which is the key to minimizing the impact of the use of phytosanitary products on the environment, animals and the workers’ health.

Signed Juan Carlos Gázquez Garrido

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Project rationale

Project rationale Jan Rether - Project lead of the Residues Management Project at ECPA Juan Carlos Gázquez Garrido - Cajamar Research Centre ‘Las Palmerillas’

The European phytosanitary industry is initiating a Project in cooperation with the Cajamar Research Centre ‘Las Palmerillas’ aimed at encouraging best phytosanitary practices with the objective of showing that Mediterranean greenhouse agricultural production, is an example of good practice. Fruit and vegetables are an essential part of our diet. We all want to eat wholesome, safe and affordable food. However, many consumers are still worried about the presence of pesticide residues on fruit and vegetables, in spite of the proven safety levels for food produced in Europe. This is shown in the European Food Safety Authority (EFSA) annual report, year after year. In recent years much has been achieved and, even though compliance (97.5 %) with the maximum residue limits (MRLs) has been generalized, the phytosanitary industry is no stranger to the concern of European society and recognizes that more can be done. The European Crop Protection Association (ECPA) has launched a specific project under the new ECPA initiative to develop projects that contribute to sustainable agriculture in European in response to consumer expectations. The project aims to minimize, even more, the presence of traces of pesticides in food and increase consumer confidence in food safety. This project is being carried out together with the Cajamar Research Centre ‘Las Palmerillas’, located in the heart of Spanish greenhouse production area; Almeria. 'A trainer-training course is being developed to encourage a wider understanding and knowledge of the steps to be taken towards better waste management which will then be shared with other countries. ECPA believes that this project can help enhance the management of waste in fresh foods in the Mediterranean area and also expect get the message across to consumers that the safety of the food that reaches your table is guaranteed. That’s what we are working for every day. In this sense, the crop protection industry in Europe is committed to helping reinforce education, training and advice programs, promoting best phytosanitary practice as the best guarantee of food safety and agricultural sustainability. The aim of the initiative is to increase consumer confidence in food safety, and include courses for trainers to extend best practices in the use of phytosanitary products. "Spanish growers, and in particular Almeria’s, have done and are doing an excellent job, optimizing the use of phytosanitary products. It is the best practices of our growers in the use of these solutions, which ensure the effectiveness, security and profitability of their business”.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Project rationale

Cajamar Research Centre ‘Las Palmerillas’ "Las Palmerillas” is located in Almeria, in the southeast of Spain and has the largest concentration of greenhouses in the world, over 27.000 hectares. It is the reference centre for knowledge in greenhouse cultivation in Spain. Cajamar Research Centre ‘Las Palmerillas’ is a technological centre for modern protected agriculture and sustainable development. It has a background stretching back nearly forty years heavily marked by the applied nature of its research projects and by its dedication to food industry sector knowledge transfer. The research centre was founded in 1975 by Caja Rural de Almeria, as it was known then, to test and study new materials, structures, techniques and systems which could provide solutions to the agricultural problems arising in the province. Caja Rural played a very important and intense role in those days and another two research centres were soon to be set up. Regarding horticulture, most species of economic interest have been the object of study at the centre, as have the evaluation of new varieties, the optimitation of cultivation techniques, physical aspects of greenhouses (structures, materials and climate management), and very intensely aspects related with the water use in greenhouses (crop water

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Project rationale

requirements, application systems and irrigation scheduling) and the soilless crop management. The newest creations are the areas of biotechnology and the environment. The biotechnology area is to explore the use of microorganisms for the production of valuable products, including product selection and suitable microorganisms, the study of the production process, the development of the necessary technology for the recovery or use and development application. At present the work being carried out in this area is focused on the commercial applications of microalgae, in the case of developing industrial production processes of these microorganisms for various purposes. Thus, work is being carried out both on the development of high-value applications in closed photobioreactors (nutraceuticals, cosmetics, animal nutrition), as in the massive low price applications in open reactors (biofuels, biofertilizers, etc.). The Environment area focuses on the dissemination of the culture of sustainability in general and particularly in combating the progress of aridity through an innovative model of plant cultivation, planting strategies involving the use natural resources and social participation. Integrating biological pest control for conservation in these processes of environmental restoration such as the creation of islands of native vegetation around the greenhouses to help recover all the biodiversity lost by the establishment of a greenhouse area is another of the objectives to be achieved in this area.

Cajamar Research Centre ‘Las Palmerillas’

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Project rationale

The total surface area including all facilities is 14 hectares.     

Main building Laboratories 27 Greenhouses = 25.000 m2 8 Hectares of fruit production 1.800 m2 Environmental area

The research team comprises 40 people including     

Researchers Technicians University students Administrative and Farm Staff

One of the main objectives of the Cajamar Research Centre ‘Las Palmerillas’ is the diffusion of knowledge which is the fruit of the results of numerous tests performed and its transfer by means of courses, seminars, guided visits, designed for technicians, growers and other professionals related with the agrifood sector. In 2012 there were over 6.500 visitors from more than forty different countries and 4.000 visitors have attended the 60 plus workshops and seminars organised.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses

Almeria, an example of Integrated Pest Management in mediterranean greenhouses Juan Carlos Gázquez Garrido Cajamar Research Centre ‘Las Palmerillas’

Introduction

The current trend in crop protection is oriented towards the production of quality food, without neglecting environmental protection. It is therefore important to reduce the use of chemicals that can be harmful to the health of people and the environment and guide phytosanitary protection towards methods that take this into account, such as biological control. This form of food production attempts to make the most of natural resources, while maintaining the profitability thresholds and production levels agricultural estates need to be competitive, producing healthy foods that respond to requirements of ever-more demanding markets and consumers. The European Union (EU) has established a framework for community action to achieve sustainable use of pesticides. The proposed measures include, in particular, the strengthening of surveillance, training and user information, as well as specific measures concerning the use of these substances. Integrated pest management (IPM) is a control strategy that is basically the rational application of a combination of biological, biotechnological, chemical, cultural or plantbreeding or selection, so that the use of phytosanitary products is limited to the minimum necessary. These control measures must be combined intelligently in order to maintain population levels of phytophagous pests below their economic damage thresholds.

2 Current situation in the Mediterranean arc: Almeria, an example of a hard task done well Unlike northern European countries, all Mediterranean countries have a special problem regarding insect control since there is a higher incidence of disease and pests. The requirements arising from food safety and the growing awareness for environmental protection are encouraging the adoption of new production methods in agriculture based on a more sustainable development model. In the intensive greenhouse crops of southeastern Spain priority has been given to the implementation of biological control seeking to minimize the use of synthetic phytosanitary products.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses The situation regarding the levels of phytosanitary product residues on horticultural produce in Almeria, has improved dramatically in recent years. In 2007, following the problems with pesticide residues detected on exported produce and the increase of resistance to pesticides by pests, there was a change of mentality in the sector in relation to pest control. The use of biological control became widespread and the key was integrated pest management. Currently, there are 27.000 hectares in Almeria using biological pest control, giving it pride of place on the international scene as the largest concentration of greenhouses in the world to use biological pest control.

Aerial view of “Poniente” or western Almeria, southeastern Spain

The chart 1 shows the evolution of hectares of crops using biological control in Almeria. The great change took place between 2006 and 2008, from 1.100 hectares to 11.100 hectares. However, for such a such radical change to take place it is necessary for the alternative proposed to unambiguously improve the situation as was the case in Almeria, implementation of IPM improved the state of affairs from both the technical and commercial points of view.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

12-13

11-12

10-11

09-10

08-09

07-08

06-07

05-06

Surface (has)

Almeria, an example of Integrated Pest Management in mediterranean greenhouses

Season Chart 1: evolution of surface area using Integrated Pest Management in Almeria.

At present, the vast majority of horticultural crops in southeastern Spain is grown using Integrated Pest Management programs and are certified by quality systems such as GLOBALG.A.P. They are governed by the standards of prevention, observation, informed decision-making and intervention. The key to ensuring sustainable production of high quality food lies in the responsible use of all the tools available to protect plants from pests and diseases, including the rational use of phytosanitary products, in accordance with best agricultural practices and the principles of Integrated Pest Management (IPM). Integrated pest and disease management strategies are based on the integration of the following control measures, which prioritize preventive, technological and biological measures regarding the application of phytosanitary products. a) Application of preventive and crop management measures  Improvement of greenhouse structures to allow better hermetic seal and better climate control  Use of more effective anti-insect mesh  Using the most suitable plant material, use of rootstocks and varieties resistant to viruses  Management of greenhouse ventilation  Optimized cultural techniques (leaf stripping, inoculum removal, etc.) b) Application of technological control measures  Chromotropic traps  Pheromone traps for mass trapping  Pest control by sexual confusion

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses c) Biological control Priority is given to the use of beneficial insects available for pest control and their development is encouraged d) Application of other phytosanitary defences, such as inducing plant defences or use of plant extracts e) Chemical Control: Finally, if necessary, resort to the application of selective pesticides which must be very respectful with beneficial insects

3 Key factors behind the success of integrated pest management in Almeria The main motivation that led to the production sector in Almeria to implement integrated control strategies was to respond to the "requirements of the supermarkets". Amongst the most important factors that have enabled this change we may cite the following: a) Public and private research and innovation, which improved the results of biological control. Initially, protocols developed in northern European countries were applied for biological control; they were not 100 % effective because the organisms were not adapted to the Mediterranean climate. Therefore, in recent years protocols adapted to southeastern Spain, with the release of native organisms such as Nesidiocoris tenuis (2003) and Amblyseius swirskii (2005), have been implemented

Orius laevigatus

Amblyseius swirskii

Nesidiocoris tenuis

b) Training of the stakeholders, by both private and public research facilities (CAJAMAR, IFAPA, COEXPHAL, UAL, HORTYFRUTA ...) have carried out an important task educating both technicians and growers alike in both pest and natural enemy management. The success of integrated pest management, successfully applied by technicians, has aroused widespread interest, encouraging many growers to participate in specific training courses c)

Significant presence of technicians (1 technician for every 5 growers) to carry out exhaustive monitoring and provide appropriate advice

d) Administrative support from Regional Government (Junta de Andalucía) through grants and courses during the first years, which, in the case of the pepper crops played

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses a very important role, however, in the case of tomato years later has not been necessary e) The willingness of growers to innovative and change and great ability to adapt.

Group of growers during a training course

Bombus terrestris on a tomato flower

Current situation - supermarket demands

Nowadays in the greenhouses of the Mediterranean area, there is strict compliance with the law, that is to say that only authorized active ingredients are used at recommended doses and safety periods are respected. New active ingredients have also been developed which are specific and very beneficial insect friendly. Although the first instrument for achieving the goal of producing high quality safe food for consumers should be the legally established European regulatory framework, in reality this is not really so. Even though the grower complies with these regulations, and is certified by global systems (eg: GLOBALG.A.P.) where large number of analyses are carried out as part of the self-monitoring process, this is still not sufficient for the supermarkets, because there is a problem of lack of consumer confidence, so most supermarkets require their suppliers to track specific quality criteria, creating their own standards (Secondary Standards). In most cases, each store has its own criteria and all of them have lowered the minimum residue levels to below the maximum residue concentration legally permitted, that is to say below the MRLs. They require a percentage of the official value of the MRL and the official value of the ARfD (Acute Reference dose), this being the concentration of a substance in food which in a single meal does not represent a health risk and is expressed in mg of pesticide per kilogram of body mass. Another of the demands imposed by supermarkets has been to insist that products do not contain traces of more than 3 or 4 different active ingredients, that is to say presence of ingredients over the detection limit, which, added to the fact that in recent years legal detection limits for phytosanitary residue presence have been lowered, make the use of phytosanitary products unsustainable.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses

Fresh-cut produce row in a supermarket

The supermarket’s demands (Secondary Standards) are not governed by technical criteria and do not encourage the alternation of active ingredients. This could give rise to the appearance of resistances which would put the sustainability of European agriculture at risk by forcing the inadequate use of plant health products as expressed by the Insecticide Resistance Action Committee (IRAC). The sustainable use of phytosanitary products based on anti-resistance strategies which are, in turn, based on the alternation in the use of different molecules with different modes of action or resistance mechanism and limiting the number of applications of the same product. These restrictions are totally against proper use of phytosanitary products and are therefore causing increased resistance and putting the sustainability of our agriculture at risk. Ultimately, these requirements will increase the possibility that certain pests will become resistant to pesticides as growers have fewer products that combat these pests or diseases with. The reduction of available products hampers resistance management strategies in the field, as it is essential to have an adequate range of phytosanitary tools available to impede the development of resistances

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses

5 Challenges and opportunities for drop protection over the next decade The challenges facing agriculture focus on producing more food with fewer resources and increasing its quality to be more competitive, while being able to satisfy the consumers’ demands. However, secondary standards are actually a private contract confirming the acceptance of standards by producers which, however controversial, are still a demand for clients who can freely choose where to buy their products. The great commercial challenge is to produce residue-free (or with the minimum possible residue). This requires: a) Increase biological control to 100 % of crops b) Chemical and biological solutions are limited and are not sufficient to defend all the crops against all pests and diseases c) There is a need for new active ingredients, which in addition to being effective must also be beneficial insect friendly and leave very little residue d) Improve emerging pest control Nezara, Creontiades, Phenacoccus... There are pests for which control methods are very limited be they chemical or biological

An adult female Southern green stink bug (Nezara viridula) (Photographed just south of Koper, Slovenia.

Creontiades pallidus (http://elhocino-adra.blogspot.com.es/)

Mature Female of Phenacoccus solani on Malva (Israel (Aut: Assafn))

(Aut: Yerpo))

e) Before, chemicals used were broad-spectrum and now they are very selective. On one hand this gives rise to new pests and on the other that resistances may appear f) It is necessary to optimize the use of fungicides, most residue problems are due to fungicide application, so it is necessary to improve structures to control greenhouse climate and carry out disease control using microorganisms g) However, it is essential to continue the search for solutions for pests for which there is no effective biological solution. In peppers lepidoptera control is pending, which has hitherto been largely solved by the use of the polyhedrosis virus. In other crops, such as tomatoes, an effective predator for whiteflies, thrips or the russet mite (Aculops lycopersici) is still required

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Almeria, an example of Integrated Pest Management in mediterranean greenhouses

Damage caused by Aculops lycopersici on a tomato crop

h) Companies producing natural enemies, despite reduced sales margins should further investigate to provide us with new beneficial insects with which to control some of these new pests i) It is also necessary to incorporate sustainability measures to pest control. Here at the Cajamar Research Centre we are working on incorporating plant barriers as a reservoir for beneficial insects outside the greenhouses It is necessary to carry out public awareness and dissemination campaigns to show consumers how we do things (best agricultural practices) in order to change social perception and nurture consumer trust. The results show that residue management carried out in Spanish greenhouses is among the best in its class. Nevertheless, we continue to strive to improve it even more, day by day.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse structures

Greenhouse structures Juan Carlos López Hernández Greenhouse Technology Area Cajamar Research Centre ‘Las Palmerillas’

Introduction

The energy crisis that took place in the 1970s could be considered as the principal reason for the development of horticulture in the Mediterranean; due to the increase in the energy cost, the surface area of greenhouses in northern Europe remained stable or decreased, while it increased in areas where heating necessities were much less. The Mediterranean horticulture benefitted from the greater availability of light in autumn and winter and the gentleness of the winter climate thanks to the proximity of the sea in the areas of production. (Castilla y Hérnandez 2005). The energy scenario lead to the establishment of two, clearly differentiated, models of production. On one side the northern greenhouses adopted high technology, greater light transmission, energy-saving technology for heating and optimised all the production means in order to reach raised higher yields. Today, the large majority of greenhouses in the North use glass as their cover of choice. On the other hand we have the Southern or Mediterranean greenhouses, adapted to local conditions with moderate investment and very few (or no) climate control systems apart from natural ventilation; this generates sub-optimal conditions in the production of crops resulting in fewer harvests than in the technologically advanced greenhouses. The large majority of Mediterranean greenhouses use plastic (in particular plastic film) as the covering material. (Castilla 2005).

Principal types of greenhouse in the Mediterranean Basin

2.1 Locally made or crafted greenhouses These types of greenhouse are usually low cost structures with little control in the way of ventilation; they are built using local materials (e.g. Wood) and are covered with polyethylene plastic laminate. The Parral type greenhouse (figure 1) is possibly the most extensively used example of this type of structure with regards to surface cover. In Almeria (Spain), alone, it covers an area of approximately 27.000 ha (EFSA 2009). The Parral greenhouse is made up of a vertical structure of rigid pillars (of wood or steel) on top of which a double net of wire is placed that serves to fix the plastic laminate roof. Just as in other areas of the Mediterranean, the availability and price of the local materials as well as the construction expertise has been fundamental in the expansion of this type of greenhouse. The advantage of these types of locally made or crafted greenhouses is the low investment, which makes it the most appropriate for running by small-scale growers. They also have some important problems associated with the design, such as the lack of hermeticism, the low 18

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse structures

transmissivity of radiation in winter, etc. However, perhaps the main inconvenience is that natural ventilation is insufficient, this is due to: 



Limited ventilation area, which is the result of a bad combination of side and roof ventilation and to the construction of small roof vents due to the growers’ fear of sudden strong gusts of wind, and that the automation of the opening and closing of these vents is anecdotal. Inefficient vent design: hinged roof windows are always preferred compared to roller type given that they achieve higher rates of ventilation although they are of the same size (almost three times more exchange of air according to Pérez-Parra et al., 2004). The use of low-porosity anti-insect mesh. As will be discussed later, the anti-insect mesh that is put over the vents greatly reduces the level of air exchange in the greenhouse. The limited distance between the greenhouses in many production areas, which greatly reduces the ventilation, especially side ventilation.

Figure 1: Parral type greenhouse

In relation to light transmission, as well as the properties of the cover materials and the number of opaque support structures, the computer simulations show that during the winter, an increase in the slope of the greenhouse roof by 11 ⁰C to 45 ⁰C can increase daily light transmission by 10 % (Castilla 2005), as a reduction of the losses caused by reflection. In practice, it is more useful to find a compromise between having good light transmission and low construction costs, so that the majority of new greenhouses have a sloping roof of 25 - 30 ⁰C.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse structures

2.2 Plastic covered industrial greenhouses A number of structures can be included in this group (multi-span greenhouses, asymmetrical multi-span greenhouses, saw-tooth type greenhouses, multi-tunnel curved roof type of greenhouse, etc.).The multi-span curved roof system is prevalent among the industrial types of greenhouse, in the majority of cases covered with plastic film or, in some cases, with rigid or semi-rigid materials (preferably polycarbonate). Frequently the roof is covered with plastic film while the front and sides are covered with semi-rigid plastics. (Figure 2) The multi-tunnel arcshaped ones are normally built of galvanised steel and are preferred by ornamental growers and nurseries. The multi-tunnel type greenhouses are more hermetic than those craft built and easier to equip with cooling, heating and/or computerised climate control. In general, this group includes greenhouses which normally have more efficient ventilation systems: the roof windows are usually larger than those in craft built greenhouses and have at least one large window per span (there have also been ones found to have double windows in each span., Figure 2). The arc-shaped multi-span type greenhouse has many advantages but also some problems. On one hand, condensation in the highest part of the arch can occur, so it is probable that this will drip in winter. Some attempts have been made to solve this problem, increase in the slope in such a way that the arcs are pointed (gothic) instead of semi-circular, but this doesn’t totally allow all the condensation to be collected.

Figure 2: Multi-span arc type greenhouse

2.3 Glass greenhouses Glass covered greenhouses (Figure 3) are the most common structures in the cold areas of the northern hemisphere. They are normally built in large compartments (e.g. in Holland the mean surface area of a glass greenhouse was 1.5 ha in 2003) (Bunschoten & Pierik, 2003) in order to limit the cost per unit of area, such as heat loss through the side walls. Normally, they only

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse structures

have roof ventilation which, in some cases (e.g. Venlo type) is discontinuous but there are also of the continuous type, too. The relationship between the area of ventilation and indoor greenhouse area is in many cases 25 % of the value recommended by the ASABE (ASABE 1999). The area covered by glass greenhouses in the southern countries of Europe is small, mainly due to the high investment costs. Glass greenhouses cover less than 1 % of the total surface area of greenhouses in countries like Spain. If it is decided to build glass greenhouses in an area with a warmer climate than that of northern Europe, special attention should be given to improving ventilation. The installation of side windows and continuous roof windows to increase the window area given the necessity of installing anti-insect nets is of particular importance. As will be seen further on, the combination of side and roof vents assures better levels of ventilation, as much in windy conditions (Kaoira et al., 2004) and especially with little or no wind with natural ventilation for thermal effect. (Baeza et al., 2009). It would also be interesting to think about using a cover of diffuse glass, to improve the efficiency in the use of light on the part of the grower, and to avoid problems of excess direct light in areas of the actively growing crop during times of high sunlight, such as the use of exterior shade systems or if not possible, to whiten it. In Holland, with a small percentage of cloudless days, they have measured increases in the harvest of up to 10 % compared to normal glass. (Hemming et al., 2006)

Figure 3: Venlo type glass greenhouses

2.4 Conclusions on greenhouse structures Increasing the transmission of winter light is good agricultural practice, and very important in the Mediterranean area. In order to accomplish this, new greenhouses should have a sloping roof of 25 - 30 ⁰C. The locally made or crafted greenhouses, if they are well designed, are appropriate for areas with a milder climate. The main advantage is the low cost of investment; the main disadvantage is the lack of climate control (especially deficient ventilation). The industrial type of greenhouse with plastic roofs can modulate unfavourable external conditions, therefore

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse structures

providing better security and stability in the greenhouse crop. However, the cost-profit analysis could be worse than that of passive greenhouses. Glass greenhouses are excellent structures, but they are rare in the southern European countries mainly due to the high investment costs.

References ASABE Standards. 1999. Heating, ventilating and cooling greenhouses, ANSI/ASAE Standard EP406.3 Baeza, E. J., J. Perez-Parra, J I. Montero, B. Bailey,J C. Lopez, J C. Gazquez. 2009. Analysis of the role of sidewall vents on buoyancy-driven natural ventilation in parral-type greenhouses with and without insect screens using computational fluid dynamics. Biosystems Engineering 104 (1), 86-96 Bunschoten B; Pierik C. 2003. Kassenbouw neemt weer iets toe. CBS Webmagazine (Centraal Bureau voor de Statistiek) Available from: http://www.cbs.nl/nl-NL/default.htm Castilla, N., Hernández, J. 2005. The plastic greenhouse industry of Spain. Crónica Horticulturae, 45(3): 15-20. Castilla, N. 2005. Invernaderos de plástico: tecnología y manejo. Ediciones Mundi-Prensa. Madrid. EFSA, 2009. EFSA-PPR project on "Data-collection of existing data on protected crop systems (greenhouses and crops grown under cover) in Southern European EU Member States". Ed. N. Sifrimis. Agricultural University of Athens. Hemming S., F. Kempkes, N.van der Braak, T. Dueck and N. Marissen. 2006. Greenhouse Cooling by NIRreflection. Acta Horticulturae 719: 97-106. Kacira, M. S. Sase, L. Okushima, 2004. Optimisation of vent configuration by evaluating greenhouse and plant canopy ventilation rates under wind-induced ventilation. Transactions of the ASABE. Vol. 47(6): 2059-2067 Pérez Parra, J., Baeza, E., Montero, J.I. and Bailey, B.J., 2004. Natural ventilation of Parral Greenhouses. Biosyst. Eng. 87(3), 355-366.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean

Greenhouse covering materials in the Mediterranean Juan Carlos López Hernández Greenhouse Technology Area Cajamar Research Centre ‘Las Palmerillas’

Introduction

The use of plastic sheeting on greenhouse roofs along with the energy crisis of the 1970s contributed to the initial relocation of greenhouses from northern Europe to the Mediterranean region. The climatic advantages that distinguish the Mediterranean region for greenhouse cultivation are associated with good availability of sunlight in autumn and winter, mild temperatures and climate stability given its proximity to the sea (Castilla and Hernández, 2005). Under these conditions, plants adapt to suboptimal climatic levels, while in northern European greenhouses (cold areas) optimal climatic conditions are created in order to maximize production. Greenhouse cultivation systems in northern Europe, which mainly use glass roofing, are known for utilizing high technology as well as for being well-equipped and expensive, resulting in high levels of energy consumption. On the contrary, the Mediterranean agricultural system, which chiefly relies on plastic covering, is characterized by low technology, basic equipment, inexpensive costs and limited energy consumption (Castilla, 2007). Experiments carried out in the Mediterranean area (Magan, 2009) in which glass greenhouses were compared with plastic greenhouses showed similar production and quality for vegetable crops. These results suggest that the use of glass greenhouses is not necessary for warm climates since they do not improve productivity in comparison with plastic greenhouses and, in addition, they require greater investment. Glass greenhouses are systems that have been developed for colder climates, thus explaining their reduced ventilation. Therefore, the use of unmodified glass greenhouses in warm areas creates difficulty in reducing the heat load. In choosing roofing material, the regional climate and location of the greenhouse must be taken into account, in addition to the optical and mechanical properties of the material (Waaijenberg and Sonneveld, 2004). In general, optical properties in greenhouse covering material should transmit the maximum amount of solar radiation (it must not retain dust and any dirt must be easily washed away) and the minimum amount of longwave radiation (this reduces heat loss at night).

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean

Plastic materials for greenhouse coverings

The plastic material used for greenhouse coverings is composed primarily of polymers and additives. Plastic greenhouse coverings typically measure between 80 and 220 micrometers (µm) thick and up to 20 meters wide. Currently, plastic films are available in mono-layer or trilayer forms (CEPLA, 2006). Greenhouse coverings have evolved since their launch in the 1950s. Currently the lifespan of these coverings reaches up to 45 months (as compared to 9 months some decades ago), depending on the light stabilizers used, geographic location, the use of pesticides, etc.

2.1 Polymers Polymers are large macromolecules whose size is achieved by the joining of smaller molecules called monomers, similar to links in a chain. The most common polymers are low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) and butyl acrylate (EBA), which represent over 80 % of the world market, including PVC in Japan and linear low density polyethylene (LLDPE) in the rest of the world. One feature that is common to all plastic films is their low density compared to traditional materials such as glass. The density of plastic is an advantage because it facilitates the handling, placement and transport of the material, the greenhouse structures are less rigid, etc. For example, 1 m 2 of LDPE film with a thickness of 200 m (800 gauge) weighs about 184 g, a film covering with the same PVC dimensions weighs about 260 g, while a glass panel measuring 1 m 2 and 4 mm thick weighs 8 kg, thus confirming that the requirements for a glass support structure must be greater than those for structures which support plastic material.

2.2 Additives These are substances that are added to others in order to give them qualities they lack or to improve the ones they have. In the case of plastic, additive materials are those which are physically dispersed in a polymer matrix without affecting its molecular structure and, when added in small quantities during the manufacture of agricultural plastic, improve its performance by promoting a longer lifespan and greater effectiveness. Since plastic was first manufactured and marketed it proved necessary to insert additives into the polymer matrix in order to process and to improve the properties of the product obtained. Therefore, its use is not optional: they are essential ingredients that can make the difference between success and failure in the development of polymer technology. Just as the field of plastic application has grown, so has the world of additives.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean

Photoselective properties of greenhouse coverings

3.1 Stabilization against ultraviolet light Solar ultraviolet radiation (UV) is primarily responsible for the deterioration of agricultural films during their exposure to weather elements, and that includes wavelengths with higher energy content. The polymers are susceptible to photooxidative deterioration processes. The end result is film degeneration and the loss of physical and mechanical properties. The additives used, depending on the stage and the way in which they exert action, operate by absorbing UV radiation, the deactivation of the excited states or free radical scavenging.

Figure 1: greenhouse with deteriorated film covering

3.2 Clear and diffuser plastic In areas with high radiation and light cloud cover, the radiation received inside the greenhouse during warm periods can cause problems in crops due to excessively high temperatures which result in burns. To avoid this situation, plastic coverings have been developed to increase the proportion of scattered radiation inside the greenhouse. In climates with elevated solar radiation, films with high light diffusion keep plants from developing burns and they reduce shading, thus making this type of material the most recommendable in these cases. Clear films are best suited for locations with less solar radiation, as most light is transmitted directly.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean The increase in diffuse radiation promotes greater, more uniform production due to a higher level of efficiency (Castilla, 2007). The extensive use of covering materials with high diffusion power in the Mediterranean area reduces direct sunlight entry into the greenhouse, increasing diffuse radiation (Cabrera et al., 2009). Crops such as vegetables with a large plant height utilize diffuse radiation better than direct radiation since diffuse radiation facilitates better median plane penetration, resulting in improved horizontal distribution of radiation (Hemming et al., 2008).

Figure 2: clear plastic greenhouse covering (left) and diffuser plastic covering (right)

3.3 Thermoplastic The atmosphere absorbs 25 % of incident solar radiation. Moreover, it is able to absorb most of the energy emitted from the land surface, because the gases it contains (water vapour, carbon dioxide, ozone, etc..) have absorption bands in the far infrared (IR) . However, there are some areas where there is no absorption and that energy escapes into space. These are called atmospheric windows, the most important of which is between the fundamental absorption of water vapour and carbon dioxide (8 and 13 µm) as it is the largest and matches the emission maximum mentioned above. Plastic film is considered to be thermal when infiltration of less than 25 % of heat radiation between 7 and 13 microns is possible. Low density polyethylene, which is the most widely used polymer in agricultural films, is very transparent to these wavelengths. Two main solutions have been adopted by the industry to increase the opacity of this material to IR: the use of additives (preferably mineral types: silica, silicates, carbonates, etc.) and the use of EVA copolymers by blending or coextrusion as it has absorption bands in the IR wavelength range of interest.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean

3.4 Anti-drip plastic The formation of water vapour condensation on the surface of agricultural plastic reduces the transmission of light and also causes small water droplets to form on the roof of the greenhouse. The resulting continual drip inside the greenhouse can cause plant diseases, viruses or burns as a result of the lens effect of the water droplets. Additives with a anti-drip feature modify the surface tension of the film to form a uniform sheet of water which, with the appropriate inclination of the material, can remove surface droplets by increasing the transmissivity of the material and reducing the risk of burns (magnifying glass effect) and diseases (fungi).

Figure 3: anti-drip effect on the condensation of water on plastic. On the left, no anti-drip material, on the right, anti-drip material

Different methods exist to ensure that the condenses in a uniform film on the surface of the plastic (outer surface treatment, surface oxidation of the polymer, polymer grafting, etc.), but the most widely used industrial application in the field of agricultural films has been the incorporation of an additive into the polyethylene (or EVA copolymer) to produce the compound. This additive progressively migrates to the surface, making it more polar and increasing its surface tension. These additives in plastic do not have a long lifespan and current research is trying to solve such drawbacks. As regards duration, one solution that appears to be promising is the production of tri-layer films and the use of the core layer as an anti-drip additive reservoir to replenish what is lost in the layer located towards the inside of the greenhouse.

3.5 Anti-heat plastic Among the most promising new developments in plastic are those that incorporate additives to block NIR radiation. Only half the energy entering the greenhouse from solar radiation is within the range of useful radiation for plant photosynthesis (PAR, Photosynthetically Active Radiation). The remaining energy is in the range of near infrared radiation (NIR) which heats the greenhouse, crops and facilitates transpiration, which may not be desirable at times (Montero et al., 2008).

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean In some geographical areas it is advisable to reduce the transmission of non-luminous solar thermal energy (NIR), ranging approximately between 760 and 2500 nm. Overheating is very frequently avoided by using shading nets inside the greenhouse or by bleaching the plastic film using a bleaching product on the outer surface of the covering. Both solutions have one negative effect: in addition to reducing NIR transmission they also reduce the PAR (400-700 nm) that should always be kept as high as possible. Among the alternatives that have been studied, currently there is only one that is applicable to polyolefin flexible coverings. It is based on the inclusion of interference pigments as additives in the formulation of the films which cause a reflection of NIR radiation. In addition to reducing NIR radiation, additives on the market today also partially reduce PAR, therefore making it necessary to evaluate their use on a case-by-case basis.

3.6 Anti-pest plastic The two insects that cause major problems in greenhouse crops are Bemisia tabaci (whitefly) and Frankliniella occidentalis (thrips), mainly for transmitting viruses to crops. The mobility of these insects depends on the presence of ultraviolet radiation from the Sun. Therefore, reducing this radiation through the use of plastic that absorbs it limits the presence of insects. However, the absence of UV radiation also limits the mobility of pollinating insects such as the Apis mellifera (honeybee) and the Bombus terrestris (bumblebee). Experiences in the Mediterranean environment (Corpus et al., 2009) show that bumblebee pollination is not affected under this type of plastic but that honeybees are more sensitive. It is therefore recommended to place the hives quickly so that pollinators get accustomed to the environment, increase the number of hives per surface or place the hives near the greenhouse windows.

References Cabrera, F.J., Baille, A., Lopez, J.C., Gonzalez-Real, M.M., Perez-Parra, J. 2009. Effects of cover diffuse properties on the components of greenhouse solar radiation. Biosystems Engineering, 103: 344-356. Castilla, N., Hernández, J. 2005. The plastic greenhouse industry of Spain. Chronica Horticulturae, 45(3): 15-20. Castilla, N., Hernández, J. 2007. Greenhouse technological packages for high-quality crop production. Acta Horticulturae, 761: 285-297. Cepla, 2006. Plásticos para la agricultura. Manual de aplicaciones y usos. Editores J.C. López, J. PérezParra y M.A. Morales. Almeria, Spain. pp 144. Hemming, S., Dueck, T., Janse, J. Van Noort, F. 2008. The effect of diffuse light on crops. Acta Horticulturae, 801: 1293-1300. Magan, J.J., Marin, S., Lopez, J.C., Perez-Parra, J., Baeza, E., Gazquez, J.C. 2009. Performance of a cucumber crop under a plastic greenhouse and a glasshouse in the Spanish southeast. ISHS International

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse covering materials in the Mediterranean Symposium GreenSys-2009: High Technology for Greenhouse System Management. Quebec (Canada). Acta Horticulturae (in press). Montero, J.I., Stanghellini, C., Castilla, N. 2008. Greenhouse Technology for Sustainable Production in Mild Winter Climate Areas: Trends and Needs. ISHS Intern. Symposium “Strategies towards Sustainability of Protected Cultivation in Mild Winter Climates”. Antalya (Turkey). Acta Horticulturae (in print). Pérez, C.; López, J.C.; Gázquez, J.C.; Marín, A. y Bermúdez, M.S., 2009. Experiencias con plásticos antiplagas en cultivos de tomate y sandía. VI Congreso Ibérico de Ciencia s Hortícolas (SECH). Logroño. Acta de horticultura, 54: 204-205 Waaijenberg, D. y Sonneveld, P.J. 2004. Greenhouse design for the future with a cladding material combining high insulation capacity with high light transmittance. Acta Horticulturae. 633: 137-143.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse ventilation and cooling

Greenhouse ventilation and cooling J.C. López1; J. Pérez-Parra1, J.I. Montero2, E. Baeza1, A. Antón2 1

Cajamar Research Centre ‘Las Palmerillas’ Institut de Recerca i Tecnologia Agroalimentàries (Institute for Agrifood Research and Technology)

Introduction

With the development of protected horticulture in warm climates the need to reduce greenhouse temperature has also arisen, to the advantage of crops as well as growers’ working conditions. For years now, but especially over the last decade, different experiments on greenhouse refrigeration during the hottest part of the day have been carried out. Summing up it could be said that there are four main factors which enable maximum temperatures to be limited (Montero et al., 1998):    

The reduction of solar radiation reaching the crop (whitewashing, shading, etc) Ventilation Refrigeration by water evaporation (misting, “cooling system”, etc.) Evapotranspiration of the crop, refrigeration by the evaporation produced by plants

These four factors are interconnected in such a way that if one changes, so do the others. For example, shading reduces greenhouse air temperature but in most cases it also reduces the amount of transpiration. One effect slows down another, which is why it is necessary to study the different cooling systems as a whole. From the combined study of the different ways to cool we can reach the following general conclusions: 1. Shading has a greater effect on a greenhouse climate when ventilation is scarce. For example, if the replacement rate is ten volumes per hour (“Parral” greenhouses with few vents) a white mesh will lower temperatures by 3 or 4 ⁰C, whilst if it is 60 ⁰C the temperature will only go down by 1 ⁰C 2. Shading is more effective in the reduction of temperature in tissues with low transpiration rates (fruit and flowers) than in tissue with high transpiration rates (leaves) 3. In greenhouses without plants or with a recently transplanted crop, shading greatly reduces he temperature (by over 10 ⁰C in many cases). However, when there is another cooling source, be it crop transpiration, water evaporation or an increase in ventilation rates, shading has a lower relative importance and less effect on the internal climate 4. Whilst the evaporation equipment is running the greenhouse must be ventilated. It is a mistake to close the vents when the fog system, or other similar devices, is running. Furthermore, if the ventilation is high the humidifying equipment must have sufficient capacity to add water vapour to compensate for that which is being lost through the open vents. The figure of 20 to 30 renovations per hour seems to be a good average and it is a

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse ventilation and cooling

figure which can be reached in the majority of greenhouses with roof ventilation, even on calm days In the first phases of crop development (low transpiration rates per unit of surface area), the cooling by evaporation equipment is extraordinarily effective, even in humid climates, and temperature reductions of between 15 and 20 ⁰C in greenhouses with bad ventilation have been achieved. In this review of cooling methods we consider it convenient to recap the latest developments in natural ventilation and in the use of humidifiers.

Natural ventilation

2.1 Wind condition: calm The least favourable conditions for natural ventilation occur when there is absolute calm. These conditions of total calm rarely occur for long enough to justify experimental measures. That is why laboratory tests are used to help analyse the behaviour of a greenhouse in calm wind conditions. Figure 1 shows the increase in temperature, with regards to the exterior, of four greenhouses according to the amount of heat the greenhouse air receives (Montero et al., 2001). For example, on a sunny summer’s day solar radiation levels inside the greenhouse are around 700 W/m2. If the greenhouse has a well developed crop, a large amount of this radiation (up to 70 %) will be used by the crop to evaporate water. In this case the net heat received by the greenhouse air will be approximately 210 W/m2. If the greenhouse contains a crop which has just been transplanted the amount of heat received by the greenhouse air will be 700 W/m 2. According to the figure, greenhouse 1, which has side vents of 16 % with regard to the floor surface, has an excessive thermal rise. Temperature conditions are much better when the side vents are 33 % the floor surface area. Figure 1 also shows the importance of combining side and roof ventilation; ventilation would appear to be sufficient with 10 % of the side vents and 10 % of the roof vents (greenhouse 3). These minimum recommended percentages of vent size should be increased when anti-insect mesh is fitted. This is described below.

2.2 Wind effect ventilation 2.2.1 Visualisation experiments As well as direct field measurements of the ventilation rate using a gas tracer and registering the fall of gas concentration over time, flow visualization experiments can be carried out to help understand how air moves in a greenhouse. Figure 2 is an example which shows the windspeed field in a tunnel greenhouse (Montero et al., 2001). One of the main conclusions to be drawn from that figure is the importance of the roof vent design. For example in figures 2.1 and 2.4 it can be seen how the air goes from one

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse ventilation and cooling

side of the roof vent in the “shade” hardly influencing air circulation within the greenhouse. However, when the roof vent allows the wind to be captured (figure 2.3), the ventilation rate increases considerably. This observation appears to indicate that hinged vents (those with reclining flaps that enable the opening or closing of the vent) are more efficient than those which are rolled up on the same plane as the greenhouse roof. This is due to the fact that the first type allows the wind to be funneled into the greenhouse while with the second type the wind could just pass over the top without entering through the vent, in the same way as in figure 2.4. Field measurements have proved this hypothesis to be valid, as will be commented below. Other visualization experiments in multi-chapel greenhouses compared the windward and leeward hinged roof vents. Apparently, roof vents opening into the wind produce a higher ventilation rate than leeward vents. On the contrary, airspeed inside the greenhouse is more uniform with leeward rather than windward ventilation due to the fact that direct air currents to the crops are avoided. “Parral” type greenhouse ventilation: Parral greenhouses make up 98 % of the greenhouses in the province of Almeria, hence the interest in studying the natural ventilation of these structures. Amongst the structures included in the “parral” group of greenhouses, the most commonly built is the multi-chapel or “raspa y amagado”. The studies into this structure currently underway at the Cajamar Research Centre ‘Las Palmerillas’, in an agreement established between Cajamar and the IRTA in Catalonia, show the way these greenhouses are ventilated and answer a number of frequently asked questions regarding natural ventilation: The results obtained show the following: 1.

When roll-up vents are installed the combination of roof and side vents improves ventilation rates, compared with just roof vents, by up to 50 % for low wind speeds (2 m s-1) whether the vents have insect mesh or not

2. The use of anti-insect mesh reduces ventilation rates by around 35 % in the case of antiaphid mesh. This happens both in greenhouses with roof vents only as in ones with combined roof and side vents 3. The type of vent used also affects ventilation rates: Hinged vents increase ventilation rates to almost twice those of roll-up vents These are the first results of a much larger ongoing research program

2.3 Cooling by water vapour evaporation The trends regarding the use of this technology may be summarized as follows: 1. The type of nozzle used is for high pressure water. In some cases low pressure systems are used which are very economic, which may be useful in Almeria during the first phases of

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES Greenhouse ventilation and cooling

crop transplanting in the summer. However, the quality of the misting is very low as is the case with the evaporation efficiency 2. Ambient humidification may be an efficient method for reducing the negative effect of saline water for some crops. For example Li (2000) obtained losses of 5.1 % for every dS m-1 in excess of 2 dS m-1 in commercial tomato production. The same crop with supplemented ambient humidity had lower losses attributable to salinity (3.4 % for each dS m-1) 3. Climate controllers currently available must be improved for the use of humidifiers to be more effective. Vapour pressure deficit (VPD) is not usually included as one of the setpoints to be maintained. It is, however, a first degree indicator of irrigation requirements or in the plant’s response to its environment. At times the combination of vent opening and humidification at the hottest times of the day leaves a little to be desired. We believe that humidification control improvement is a very interesting line of work for greenhouses in warm regions such as Almeria.

References Li (2000). Analysis of greenhouse tomato production in relation to salinity and shoot environment. Tesis Doctoral. Universidad de Wageningen. 96 pp Montero, J.I., Antón, A., Muñoz, P. (1998). Refrigeración de invernaderos. Tecnología de Invernaderos II. Curso Superior de Especialización.pp 313, 338. Montero, J. I., A. Antón, R. Kamaruddin and B. J. Bailey (2001a). Analysis of thermally driven ventilation in tunnel greenhouses using small-scale models. Journal of Agricultural Engineering Research, in press. Montero, J. I., G. Hunt, R. Kamaruddin, A. Antón and B. J. Bailey (2001b). Effect of ventilator configuration on wind driven ventilation in a crop protection structure for the tropics. Journal of Agricultural Engineering Research.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

Greenhouse climate control Juan Carlos López Hernández Greenhouse technology Area Cajamar Research Centre ‘Las Palmerillas’

Introduction

Growing conditions inside a greenhouse need to be understood not only in a qualitative way but also in a quantitatively to determine impact on production. Greenhouse climates can be quantified in relation to external conditions as well as the physical properties of the greenhouse and its facilities and equipment (Bot, G.P.A., 1995). Crop development and growth are influenced by the climate where the processes of photosynthesis, respiration, cell division, cell expansion, uptake of nutrients and water are modified mainly by temperature, vapour pressure deficit, light and CO2. Plant metabolism and the rate of metabolic reactions are affected by temperature. Growth rates can even double for many crops exposed to the cold when the temperature rises by 10 ⁰C (Day and Bailey, 1998). Extreme temperatures, be they high or low, have an effect on crops (Hanan et al., 1988), and enzymes and other proteins become denaturalized. When the temperature drops to below 10 - 12 ⁰C, thermophilic species (which can be considered to include the majority of vegetable crops produced in protected conditions along the Mediterranean coastline) show the following alterations (Lorenzo et al., 2000):  Growth reduction  Reduction of net assimilation  Respiration depression  Reduction in transport and distribution of assimilated substances  Reduction in the absorption of water and salts  Anatomical and morphological changes  Loss of fertility  Early aging of photosynthetic tissue due to cellular necrosis Temperature levels leading to maximum production are between 16 and 20 ⁰C during the night and between 22 - 30 ⁰C during the day. However, due to the high energy consumption required, these are often different to the optimum economic levels. It is therefore necessary to manage the heat input by means of climate strategies, plant training and trading markets. Climate strategies usually entail: energy saving screens, conditioning of thermal levels at different physiological stages of the crop, day-time - night-time period, temperature fluctuations, etc.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

The dependence shown on the accumulation of degrees-day (thermal integral) by the physiological response of several crops enables us to program them with regards to harvesting and production. Greater control over greenhouse temperature will determine not only an increase in production but also in fruit quality.

Energy requirements

The amount of heat necessary to maintain greenhouse temperature requirements depends basically on:  Covering material  Heat system  External conditions: Temp, Wind, etc. Simplified, energy requirements can be determined using the global heat transmission coefficient “U” which is characteristic to all kinds of covering materials: Covering material

U (W m-2 k-1)

Glass

6.0 - 8.8

Double glazing

4.2 - 5.2

Double polycarbonate

4.8

Polyethylene

6.0 - 7.8

Double polyethylene

4.2 - 5.5

Therefore, the energy required Q ( w ) to maintain a thermal leap is:

A Greenhouse area U Global heat transfer coefficient Ti Greenhouse temperature To External temperature

Heating systems

According to whether one, or several, of the ways heat can be transferred (convection, conduction and radiation), the systems may be classified as follows:

3.1 Convection heating systems These are systems which use air as their conductor. Due to their limited inertia, they allow air temperature to be increased quickly as well as cooling equally rapidly as soon as they stop

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

working. Temperature gradients and losses are high as they are usually located above the crops.

Amongst the convective systems: air heaters, indirect and direct combustion hot air generators; the last two being the most widely used: 

Indirect combustion hot air generators use a heat exchanger, separate the combustion gases and expulse them whilst sending the hot air into the greenhouse. Given that part of the heat is expulsed with the exhaust fumes the performance of these machines is between 80 % and 90 %

Figure 1: heat distribution by means of the perforated polyethylene sleeves of an indirect combustion system



Direct combustion hot air generators: both hot air and combustion gases enter the greenhouse. The fuel used must have the lowest possible amount of toxic substances; propane and natural gas being the most highly recommended

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

Figure 2: direct combustion system (burner)

It is important to control the levels of combustion gases to avoid problems for people and plants alike. The system is considered to be 100 % efficient as the heat accompanying the combustion gases is not lost.

3.2 Conduction heating systems These systems are designed to provide adequate temperature for the root area. From a physical point of view, one of the objectives of heating the soil is to indirectly use the air exchange surface offered by the greenhouse floor. This system is more efficient than the aerial heating systems (Feuilloley & Baille, 1992). The difficulty of placing the exchangers into the greenhouse floor added to the inconvenience caused when working on the soil, limited its expansion as a heating system. However, the incorporation of substrates as growing media has enabled the location of heat exchangers beneath the substrate itself. Calefacción enterrada en el suelo

Heating buried in the soil

Es necesario definir: -

el espesor de la capa de suelo que se desea calentar

- la profundidad a la que tienen que enterrarse los tubos



- la distancia entre los tubos Suelo -2 ) F < 60 (W m suelo 

y Tagua < 40°C x y

It is necessary to define

d 15-30 mm

the thickness of the layer of soil to be heated  the depth at which the pipes are to be buried  the distance between pipes Suelo = soil Agua = water

Figure 3: underground heating. (M. González-Real, 1998)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

3.3 Convection and radiation heating systems Heat transfer is carried out by means of pipes either overhead or placed over and amongst the crop. Hot water at high (up to 90 ⁰C) or warm temperatures (from 30 ⁰C to 50 ⁰C) according to the material used (metal or plastic).

3.4 Metal pipe hot water system These systems modify the air temperature which heats up when it comes into contact with the pipes or other surrounding objects (soil, plant, greenhouse cover, etc.) due to radiative exchange. Heat distribution is more uniform than with air based systems as the pipes are located close to the plants and low temperature gradients are maintained. Hot water heating systems allow heat to be distributed uniformly and are more efficient than air heating systems. However, thanks to perforated tubes which take the heat to the plant, indirect combustion heating systems have proved to be similar in efficiency to hot or warm water systems (Lorenzo et al., 2000). The greater inertia of water as opposed to air systems (chart 1), allows the climate to be controlled more efficiently except in the case of a system breakdown where, after cooling down, it will take longer return to the setpoint temperature.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

Aire caliente = Hot air Aire frio = cold Air Hora Solar= Solar Time

Chart 1: air temperature evolution (2 m) two heating systems: air and water

Stanhill (1981) calculated all the greenhouse inputs (fertilisers, water, heating, CO2, etc.) as units of energy and determined that the requirements of heated greenhouses in England were forty times greater than those of unheated greenhouses in Israel. Heating accounted for 80 % of total energy consumption; hence the importance of determining energy requirements derived from heating locally. Experiments carried out locally using different heating systems and at different temperature levels (tables 1 and 2) show the variability between seasons with regard to fuel consumption. For low temperature levels (10 - 12 ⁰C) fuel consumption was between 1.5 and 2.5 kg per m-2 for propane and even over 10 kg m-2 for higher levels (16 - 18 ⁰C). The differences between both seasons are due to the harsher winter of the 98 - 99 season.

HEATING SYSTEM Season

Air Generators (indirect Combustion)

Hot water pipes

97-98

5.6

4.7

98-99

9.9

10.8

-2

Table 1: Fuel cost (kg m ) (propane) for two heating systems and two seasons 97 - 98 y 98 - 99. Minimum daytime-nightime setpoint temperatura established during the cucmber crops: Germination: 22 / 20; fruiting start: 18 / 16; harvest: 16 / 14. (Lorenzo P. et al., 2000) (To extrapolate fuel consumption for a one hectare greenhouse multiply by 0.8)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

DIRECT COMBUSTION AIR

Season

12 ⁰C

97-98

1.2

98-99

2.4

14 ⁰C

15 ⁰C 4.3

5.1

-2

Table 2: Fuel cost (kg m ) (propane) for a direct combustion hot air system for two seasons and different setpoints: Minimum temperature: 12 ⁰C; 14⁰C y 15 ⁰C. (López J.C. et al, 2000). (To extrapolate fuel consumption for a one hectare greenhouse multiply by 0.8)

Work carried out at the: Cajamar Research Centre ‘Las Palmerillas’ in traditional “parral” (low hermeticity) type greenhouses using direct combustion, air heating systems for cucumber and bean crops at medium-low level setpoints (10 - 15 ⁰C), managing the ventilation so as to avoid high levels of gases, showed neither symptoms of toxicity nor a decrease in production. However, in arch greenhouses (more hermetic), for a crop of beans with a high temperature regime (vegetative phase 18 ⁰C and fruiting phase 16 ⁰C) the direct combustion hot air system caused symptoms of toxicity in the crop (reduction of leaf area, reduction in the length of the shoot and fruit abortions) compared to the metal tube hot water system causing a decrease in early and late production levels (chart 2). The levels of CO2 in the greenhouse with direct combustion heating reached levels in excess of 5.500 ppm during the coldest periods (tin- text > 8 ⁰C). Hence the use of these systems must be conditioned to combustion gas control and to working with low temperature regimes or maintenance (tªinv - tªext = T small) ventilating or stopping machines to avoid toxicity to people and plants.

Agua caliente = Hot water Aire caliente = Hot air

Chart 2: commercial production for a bean crop using two heating systems: Direct combustion air and water in a metal pipe

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse climate control

Installation costs for the heating systems are as follows in ascending order: direct combustion hot air, indirect combustion hot air, low temperature hot water and high temperature hot water. Installation costs for hot water heating systems are lower the higher the area to be heated as certain equipment (boiler, regulators, etc.), is common. This is not the case with the hot air systems. The cheapest system is the direct combustion hot air system. It is also the riskiest of systems to use, especially when the system is running continuously for several hours, as all the combustion gases go into the greenhouse Due to the great uncertainty surrounding horticultural produce and fuel prices, it is important to keep a continuous check on the system profitability.

References Bot G.P.A. and Van De Braak 1995. Physics of greenhouse climate pg. 125-160. Greenhouse climate control ISBN: 90-74134-17-3 Day W. and Bailey B.J. 1998. Physical principles of microclimate modification pg. 71-101. Ecosystems of the World. ISBN : 0-4-444-88267-7 Feuilloley, P; Baille, A 1992. Principes généraux d’utilisation des eaux tiédes pour le chauffage des serres. Informations Techniques du CEMAGREF, 87:1-8 González-Real (Baille) M y Baille A., 1998. Calefacción de invernaderos. Tecnología de invernaderos II pg. : 339-398. López J.C., Mateo A., Puerto H. y Pérez J. 2000. Calefacción de invernaderos en el sudeste español. Lorenzo,P; Sánchez-Guerrero,M.C; Medrano.2000. Calefacción de invernaderos en el sudeste español. Edita Hanan J.J:, Holley, W.D. and Goldsberry, K.L., 1978. Greenhouse Magnagement. Sprintger, New York, 530 pp.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

Greenhouse technology & integrated pest management Gázquez, J.C.; López, J.C.; Pérez, C., J.C.; Baeza, E.; Meca, D.; Pérez-Parra, J. Cajamar Research Centre ‘Las Palmerillas’

Introduction

With the ultimate objective of achieving crop production of a quality which is certifiable and recognizable, progress in greenhouse production systems, just like any other agricultural production system, must be designed to achieve a rational production model in terms of use of resources, environmentally friendly and which has built-in guarantees for the health of both consumers and growers alike. In recent years there has emerged an increasing preoccupation for products of the best quality and which are safe for consumers, cultivated under standards of environmental sustainability. The rational and reduced deployment of phytosanitary in controlling plant pests and diseases occupies a key role in the satisfaction of this objective. As a response to this demand for food quality and safety, the fruit and vegetable growers of Almeria have, with enormous success, put in place in recent years a change in strategy in the fight against pests and diseases. Biological control has been empowered and prioritized over chemical methods, and this new approach has been supported by intensive research work and innovation, carried out over recent decades by researchers and technicians, both from public bodies and from private enterprise. This work, which has enabled the development of essential tools; knowledge, techniques, beneficial insects, a banker plant, etc. growers and technicians need these in order to implement the biological control of pests and diseases in Almeria’s greenhouses, and it is sure to proceed at an accelerating pace, to bring about the necessary change in a way which is robust and sustainable over time. It will improve in efficiency and will be capable of responding with speed and success to the new problems which, inevitably, we will need to face in the future. In order to study the variables which affect the incidence of pests and diseases, it is necessary to think of the greenhouse as a system, with the crops, the populations of different pest species which affect those crops and the beneficial insects which are linked to them, all forming a part of that system. And we must also bear in mind that various attendant factors act upon the equilibrium of this ecosystem, such as the enclosure method of which defines it (hermetic sealing, the characteristics of the materials), the machinery installed within it (heating, cooling, CO2), or the actual management and implementation of the system. The technology used in the greenhouse, and its management, affects each and every one of the system’s living components; plants, pests and beneficial insects. This will determine the

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management severity of the phytosanitary problem in each greenhouse, and the degree of success with which it is resolved. The evaluation of the interactions between the mentioned factors and the behaviour of pest and beneficial insect populations is certain to give us useful information and ensure the success of our biological campaign to control pests. To this end, in the Cajamar Research Centre ‘Las Palmerillas’ in recent years has evaluated all the aspects of greenhouse structure, covering materials (plastic and mesh), climate control equipment and cultivation techniques which interact with the plant-pest-natural enemy nexus, with a view to determining the extent to which they influence the efficacy of biological pest control.

2 Greenhouse structures & plastic photoselective and anti-pest materials The greenhouse confines the space in which the crops grow and establishes a very important physical barrier for preventing the entry of pest insects and virus vectors which can cause economic damage to the crops. A hermetic seal, by which the communication points between the greenhouse’s interior and exterior are adequately protected - the points through which pest insects can reach the crops (vents, gates, holes) - is one of the main measures in observing integrated pest control. Chart 1, which is based on observations carried out in the Cajamar Research Centre ‘Las Palmerillas’, shows how the structure’s degree of hermetic seal affects the incidence of the Tuta absoluta, one of the most recent and most devastating pests to hit greenhouse cultivation in Almeria. 750

700

fgdfgdfgd

500 Autumn Spring 250

200 80 10

0 Parral

Multi-tunnel

Chart 1: Capture of Tuta absoluta in different greenhouse structures

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management The use of plastics known as “anti-pest” (photoselective), which block part of the sun’s UV radiation (Salmerón et al., 2001) and eliminate the colour wavelength which insects find most visible, makes it difficult for pests to prosper in the greenhouse (Salmerón et al., 2001; Antignus et al., 2001; Lapidot, et al., 2002), and also restricts the transmission of viruses by insects which are sensitive to the absence or reduction of ultraviolet radiation (Gonzalez et al., 2003; Monci et al., 2004; Rapisarda, et al., 2006). However, this anti-pest plastic may also have a negative effect on the pollinators, which have been found to need the full ultraviolet spectrum (Bertholf, 1931; Weiss, 1943; Hollingsworth et al., 1970; Varela, 1974; Brown et al., 1998; Chittka & Thomson, 2001), limiting their vision (Cabello et al., 2005 a, 2006; Soler et al., 2005), so that changed ultraviolet light conditions may change the pollinators’ perceptions of the different flower colours [pollinators being the common bee (Apis mellifera) and the bumblebee (Bombus terrestris)], making it especially difficult for them to locate the flowers among the crops (Cabello et al., 2005 b; 2006). Notwithstanding this, the negative effect can be attenuated by the capacity of the pollinators to respond, given that bumblebees are very fast learners and can quickly adapt to the absence of ultraviolet light (Dyer & Chittka, 2004). Limiting ultraviolet light reduces, and can eliminate, the growth and sporing of disease fungi such as Botrytis cinerea, or grey mould (Jarvis, 1997; Díaz et al., 2001). In order to evaluate the influence of the additive ultraviolet filters in the plastic materials on the presence of Bemisia tabaci y Frankliniella occidentalis, as well as on the natural pollinators (Bombus terrestris and Apis mellifera), the Research Centre has carried out different studies since 2005, comparing covering materials with different levels of ultraviolet radiation absorption (1 %, 10 %, 23 %, 55 % & 65 %, respectively) with crops of tomatoes, melons and watermelons.

800

F. Occidentalis (nº)

Bemisia tabaci (nº)

With regard to pest insects (chart 2), the results obtained show that anti-pest plastics which absorb ultraviolet radiation arriving at the greenhouse limit the mobility of the insects, and as a consequence their reproduction, and for this reason are an important tool in the control of whitefly and thrips in the greenhouse, the trials carried out resulting in 65 % reductions in Bemisia tabaci and Frankliniella occidentalis, as against the control (Pérez et al., 2009).

Antiplagas

600 Testigo

400 200

(a)

0 0

100 120 140

Días después del trasplante

400 Antiplagas

300 Testigo

200 100

(b)

0 0

100 120 140

Días después del trasplante

Key: red = anti-pest, green = control horizontal, bottom: Days following transplanting Chart 2: Development of accumulated numbers of Bemisia tabaci (a) and Frankliniella occidentalis (b), on chromotropic pads under plastic of 1 % transmissivity (anti-pest) and 55 % UV radiation (control)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management With regard to the pollinators (charts 3 & 4), the experimental results demonstrate that there is a specific interaction between the anti-pest plastics and the pollinator species, such that the activity of the bumblebee (Bombus terrestris) is not affected by the use of anti-pest plastics, while the behaviour of common (Apis mellifera) is (López et al., 2006; Pérez et al., 2007), with a 46 % reduction recorded in the number of bees entering and leaving the hive, which in turn led to maximum falls in production of up to 34 % (Pérez et al., 2009). Mini-watermelon crop

Antiplagas

Salidas

Testigo

Abejorros (nº)

Entradas

25 20 15 10 5 0 1

Antiplagas

25 20 15 10 5 0

Conteos

KEY: Conteos = Counts

Testigo

Antiplagas =Anti-pest

Testigo=Control

Abejas = Bees

Abejorros = Bumblebees

Chart 3: Tracking the activity of bumblebees (Bombus terrestris) under plastic of 1 % transmissivity (anti-pest) and 55 % UV radiation (control). Entradas: the number of bumblebees entering the hives during a 15-minute period of activity. Salidas: the number of bumblebees leaving the hives during a 15-minute period of activity Melon crop Salidas Antiplagas

Testigo

250 200 150 100 50 0

Antiplagas

Testigo

200 Abejas (nº)

Abejas (nº)

Entradas

150 100 50 0

Conteos

KEY: Conteos = Counts

Antiplagas =Anti-pest

Testigo=Control

Abejas = Bees

Abejorros = Bumblebees

Chart 4: tracking the activity of bees (Apis mellifera) under plastic with 1 % transmissivity (antipest) and 55 % UV radiation (control). Entradas: total number of bees entering the nest during a ten-minute period of activity. Salidas: total number of bees leaving the hives during a ten-minute period of activity

The results obtained show that the anti-pest plastics reduce the incidence of whitefly and thrips by a significant degree, without affecting the implementation of biological control. What

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management is more, bumblebees (Bombus terrestris) are not affected by the use of anti-pest plastic, while the reverse is true for Apis mellifera. Thus, on the crops which use bees as pollinators, such as tomatoes, peppers, cucumbers, aubergines, green beans and courgette, the use of anti-pest plastics can make better control of the main “parral” pests possible and improve the results obtained from biological control.

Photo 1: Flight of the bee (Apis mellifera) over a melon blossom

Photo 2: Bee (Apis mellifera) inside a watermelon blossom

Photo 3: Bumblebee (Bombus terrestris) on a tomato flower

Photo 4: Bumblebee (Bombus terrestris) on a watermelon flower

Anti-insect meshes

Pests, in particular those which act as vectors, eg Bemisia tabaci and Frankliniella occidentalis, for viruses such as Tomato Yellow Leaf Curl Virus (TYLCV) or Tomato Spotted Wilt Virus (TSWV), have become a problem of enormous economic impact for protected horticulture (Gázquez et al., 2009). To combat this, the use of meshes over vents as a physical barrier to reduce insect incursion is an indispensable method for cutting down on the application of insecticides and for improving the chances of success for biological control in intensive cultivation systems. Today, catalogues of anti-insect meshes available to growers are wide-ranging (meshes of different densities, various colours, photoselective meshes, etc.) but the need to balance the

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management efficacy of the mesh in excluding insects with adequate permeability for the free passage of air in order to maintain correct ventilation means that the process of choosing a mesh is a complex one. In recent years, various studies have been carried out in order to geometrically categorize the commercially-available meshes, and to measure their porosity (Ross & Gill, 1994; Bell & Baker, 1997; Teitel, 2001; Bartzanas et al., 2002, Cabrera et al., 2002; Valera et al., 2003, Cabrera et al., 2006), with the aim of determining both their efficacy as physical barriers against insect intrusion and their effect on the natural ventilation of greenhouses.

Photo 5: Digital image of an anti-insect mesh

Many of these studies show that the properties of the meshes are not always well-defined in advertising. Since 2002 the Cajamar Research Centre ‘Las Palmerillas’ has been characterizing meshes, analyzing their physical properties, their uniformity, their efficacy as insect barriers and their effect on the rate of air flow (Chart 5). These studies have highlighted the lack of uniformity in mesh apertures and their geometric exactness, that the properties of the meshes are not well-defined and that there is a need to define the meshes in the commercial literature and to give precise data on their characteristics. A correct definition of a mesh should include (or allow estimation of) information on the following aspects:   

The average dimensions of the aperture and the percentage of insects excluded The diameter of the strand, or both diameters in the case of a strand which is oval in cross-section, expressed in millimetres Number of strands per square centimetre, describing in the first place the number of strands in the warp, and in the second place the number in the weft (example: 20x10 strands/ cm-2)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management    

The resistance to air-flow (or porosity): the relationship between the area of the aperture and the total area Homogeneity Optical properties: spectral transmissivity and spectral reflection or absorption Mechanical properties: (resistance to ultraviolet radiation)

Chart 5: Study of insect exclusion percentages in 21 commercial meshes

The efficacy of anti-insect meshes is due both to their behaviour as a physical barrier (Bethke et al., 1994; Baker & Shearin, 1994; Bell, 1997, Bell & Weatherley, 1999; Antignus, 1999; Teitel et al., 2000; Critten & Bailey, 2002; Díaz Pérez et al., 2003; Hanafí et al., 2003; Teitel 2006), and to their action as a light filter (Bethke et al., 1994; Antignus et al., 2001; Teitel, 2001; Klose & Tantau, 2004) with the consequent negative effect on the crops. In the Research Centre, a range of different commercially-available mesh was analyzed (chart 6), emphasizing how some of them (mesh 3) bring about a major reduction in light, equally transmitted across the spectrum (around 34 %). The photoselective meshes significantly reduce the transmission of ultraviolet radiation (some 36 % and 33 %, as against 60 % transmitted through the other control meshes, mesh 1 and mesh 2). In the visible spectrum, the average transmissivity of the non-photoselective meshes (control, meshes 1, 2, & 3) is greater than 80 %, as against 61 % for photoselective mesh 1, or 50 % for photoselective mesh 2 (Gazquez et al., 2009b).

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Trasmisividad (%)

Greenhouse technology & integrated pest management

100 90 80 70 60 50 40 30 20 10 0 280

320

360

400

440

480

520

560

600

640

680

720

760

800

Longitud de onda (nm) Malla 1

Malla 2

Malla 3

Fotoselectiva 1

Fotoselectiva 2

Testigo

Chart 6: Range of different commercial meshes -2

-2

Mesh 1: Mesh 28x13 strands cm of Macrotex; Mesh 2: Mesh 30x21 strands cm Econet-t - Ludvig Svensson; -2 -2 Mesh 3: Mesh 20x10 strands cm of black colour; Photoselective 1: Mesh 21x9 strands cm BioNet - Klayman -2 Meteor L.T.D.; Photoselective 2: Mesh 21x11 strands cm OptiNet - Polysack

Effectiveness as a physical barrier depends, fundamentally, on the size of the aperture, defined in turn by the thickness and number of strands, and the size and/or morphology of the pest insect. The dimensions (thorax width and abdomen width) of the major pest insects of Almeria’s greenhouses are set out in Table 1.

T.Cabello

Photo 6: Bemisia tabaci

Photo 7: Frankliniella occidentalis

Photo 8: Tuta absoluta

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

PEST INSECT

THORAX WIDTH (micras)

ABDOMEN WIDTH (micras)

Liriomyza trifolii

640

850

Trialeurodes vaporariorum

288-400

708

Bemisia tabaci

239-320

565

Frankliniella occidentalis

192

265

Table 1: Measurements of common pest insects, present in the greenhouses of Almeria

On the other hand, as chart 7 shows, the meshes in the vents cause a reduction in air-renewal (Muñoz et al., 1999; Fatnassi et al., 2002, 2006; Kittas et al., 2002; Pérez-Parra et al., 2003; Molina-Aiz et al., 2005) (higher temperatures, more humidity, less CO2) which can easily be compensated for by increasing the ventilation surface area (Pérez-Parra et al., 2004), or there again, to obtain greater porosity with a greater exclusion of insects - which is to say, greater efficiency, strand of a smaller diameter is needed (Cabrera et al., 2006; Gázquez et al., 2009b).

Reducción estimada tasa de ventilación (%)

100 90 80 70 60 50 40 30 20 10 0

Malla 20 x 10 Malla 16 x 10

90 100

Porosidad (% )

Chart 7: Reduction in the ventilation rate (%) as a function of the porosity of the mesh (Pérez-Parra et al., 2004) [malla = mesh]

Taking into account such aspects as the three-dimensional nature of the apertures, the thoracic diameter of the insects and a small-diameter (0.19 mm) Cabrera et al (2006) defined the most efficient mesh type for the exclusion of pest insects in protected “under plastic” agriculture (Bemisia tabaci y Frankliniella occidentalis). (Table 2)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management Pest Insect / three dimensional diameter of aperture (mm)

Ø 3D (mm)

Porosity (m2 m-2) (ε)

Ventilation Reduction (%)

Type of mesh (cm strands-2)

Bemisia tabaci (Ø 3D: 0.24)

0.24

0.42

24x12

Frankliniella occidentalis (Ø 3D: 0.19 )

0.19

0.36

28x14

Table 2: Most efficient meshes for excluding the two most important pests in agriculture under plastic (Bemisia tabaci & Frankliniella occidentalis) (Cabrera et al., 2006)

Meshes and greenhouse covering materials were compared for different physical and optical properties at the Cajamar Research Centre ‘Las Palmerillas’ over three consecutive years (2005, 2006 & 2007) during the spring/summer season,

Photo 9: Different types of

Photo 10: Mesh 28x14 strands cm

-2

commercial mesh

Meshes of varying densities of strands and photoselectivity, used as covering material, have been analyzed for their influence on the productive response of a crop of tomatoes, during the summer cycle and under conditions of integrated control. The incidence of Bemisia tabaci, Frankliniella occidentalis, Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Spotted Wilt Virus (TSWV) was also measured. The results obtained (chart 8 & 9) indicate that the use of photoselective meshes, or of greater density than standard ones (20x10 strands cm-2) reduce to a significant extent the levels of Bemisia tabaci and of TYLCV (Gazquez et al., 2007). However, the use of photoselective meshes does not significantly reduce the incidence of Frankliniella occidentalis, an effect which was observed when the reduction of radiation under the mesh is important (black mesh). Notwithstanding this, the drastic reduction of transmitted radiation through some meshes (black or photoselective) has a markedly negative effect on final production. Crop output was down to 50 % for the tomato crop (Gázquez et al., 2009b).

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

Fotoselectiva 1

1000

Fotoselectiva 2

800

Testigo

600

Negra

400 200 0 0

60 80 d.d.t.

100

120

Chart 8: Pattern of Daily Accumulated Incidence (DAI) of Frankliniella occidentalis on the plant, under different commercial meshes.

900 800 700 600 500 400 300 200 100 0

Fotoselectiva 1

IDA Mosca en planta

IDA Trips en planta

1200

Fotoselectiva 2 Testigo Negra

60 d.d.t. 80

100

Chart 9: Pattern of Daily Accumulated Incidence (DAI) of Bemisia tabaci on the plant, under different commercial meshes

Cooling techniques and pest control

The need to meet the market demand for a continuous supply of products of consistent quality and quantity throughout the year is compelling the extension of the growing cycles well into the summer, when temperatures inside the greenhouse can reach beyond the optimum (T > 35 ⁰C) and moisture levels can fall, with large deficits in water vapour pressure (DPV>3 kPa). For this reason, it is necessary to use some type of cooling system in the greenhouse in order to maintain the most favourable conditions for the crops and to secure harvests adequate in quantity and quality, over longer periods of time. Adequate control of ambient greenhouse temperature is an essential factor in achieving homogenous production of quality crops over a long growing period and to intervene decisively in a multitude of the crop’s physiological processes (Gonzalez-Real & Baille, 2006). If we consider the normal growing cycles in Almeria, the need to reduce air temperature presents itself from the beginning of spring through to late autumn (Kittas et al., 1996; Montero et al., 1998). The most practical and economical strategy, and therefore the most widely used in lowering greenhouse temperatures during the day, is a combination of natural ventilation and a whitewashing of the covering (Meca et al., 2007). The incorporation of anti-insect meshes over greenhouse vents in order to protect the crops from pests and diseases is a general practice which has been widely adopted in the south eastern Mediterranean. Muñoz et al. (1998), Pérez-Parra (2002) have measured considerable reductions in the rate of greenhouse ventilation running from 35 % to 60 % for the so-called anti-mite and anti-thrips meshes, commonly used in greenhouses. These physical barriers cause the natural ventilation to prove insufficient for a thermal and hygrometric regime which is acceptable for either the growing of greenhouse crops or the natural enemies of pests which we release onto the crops.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management The major problem faced by most “parral”-type multi-bay greenhouses is the lack of adequate natural ventilation. This causes the appearance of excessive temperatures inside the greenhouse, together with other problems associated with this excessive heat, especially if humidity levels are low: “water stress”, poor fruit setting, physical ailments in the fruit (“blossom end rot”, “blotching” (uneven ripening), skin scars &c.), etc. But deficient natural ventilation also has pernicious effects during cold weather, especially as these coincide in Almeria with the height of the ripening period. The transpiration of the plants causes high levels of relative humidity. These levels, coupled with the night-time cooling of the plastic cover, lead to condensation forming on the underside of the plastic. The dripping which results favours the development of fungal and bacterial diseases in the air (Hand, 1984; Mistriotis et al., 1997; Papadakis et al., 2000). Furthermore, the layer of condensation reduces the passage of light to the interior of the greenhouse (up to 40 % in the middle hours of the day, Jaffrin and Makhlouf, 1990) limiting the trapping of light by the plants, and eventually affecting production. Further still, nutritional disorders can show up, associated with the high relative humidity. Finally, but no less important, a low rate of air renewal can cause the level of CO2 inside the greenhouse to drop alarmingly, because it is being “fixed” by the plants as a consequence of photosynthesis. With conditions of deficient ventilation, reductions of the concentration of CO2 have been measured at 25 % compared with the exterior, when winds are in excess of 1.5 m s-1 (Lorenzo, 1990); and up to 44 % with slighter winds. This has an inhibiting effect on production. The desirability of adequately ventilating the greenhouse so as to avoid problems with plant diseases and to obtain suitable conditions for the introduction and establishment of beneficial insects, above all when the placing of anti-insect meshes is inevitable, makes it necessary to design modern ventilation systems, increasing the ventilation area, incorporating more efficient vents (folding front-roller) or combining lateral and roof vents (Pérez-Parra et al., 2004) ent windows (folding front-roller) or combining lateral and roof vents (Pérez-Parra et al., 2004) On the other hand, the whitewashing of the plastic cover to provide shade brings a range of other inconveniences, such as the remaining of the whitewash on the cover even on cloudy days and the unevenness of its application (Montero et al., 1998). Improvements like the establishment and progressive washing of the whitewash (chart 10), will help considerably, both in the cultivation of the crop and in the correct development of natural enemy populations. When the combination of natural ventilation and whitewashing in periods of extreme heat does not prove sufficient to alleviate the high temperatures, the incorporation of other systems of cooling, such as forced ventilation, or cooling through fogging (artificial mist evaporation) can be alternatives to bear in mind, because they are highly efficient. But the use of technology to control excessive temperatures has an effect, which needs to be studied (so as to correct undesirable results) on the incidence of pests and their natural enemies.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

Chart 10: Recommended guideline for the management of whitewashing the greenhouse Cover (Pepper) (suelta enemigos naturales = release of natural enemies, semanas de cultivo = weeks of crop cultivation)

A research programme into greenhouse cooling has been carried out at the Cajamar Research Centre ‘Las Palmerillas’, evaluating different systems: natural ventilation, forced ventilation, fogging (both at high and low pressure), whitewashing in different concentrations and various combinations of these techniques (Aroca, 2003; Maillo, 2005; Sáez, 2005; Rodríguez, 2006; Parra, 2007; González, 2008; Meca, 2008; Gázquez et al., 2006; 2007 & 2009; Meca et al., 2006 y 2007; Pérez-Parra et al., 2005) and the effects of these cooling techniques on the incidence of pests and diseases have been quantified.

Photo 11: Greenhouse with natural ventilation

Photo 12: Forced ventilation

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

Photo 13: High pressure fogging nozzle

Photo 14: Low pressure fogging nozzle

The results (chart 11 & 12) show that the use of forced ventilation significantly increased the populations both of Bemisia tabaci and Frankliniella occidentalis as compared to whitewashing and fogging, thanks to the higher rate of penetration of the vent meshes with the falling of the air pressure caused by the ventilator-extractors. With regard to viruses and diseases, there was also a major presence of TSWV under forced ventilation, and of Botrytis cinerea under fogging (Gázquez et al., 2007).

T1: V. Forzada T3: Blanqueo

2000 MDA

T2: Nebulización

2500

1500

1000 500

0 0 Lavado del blanqueo (58 ddt)

100

150

200

250

Días después del transplante

Chart 11: Number of flies acquired daily (MDA on graph) for a pepper crop under three cooling systems (T1 = Forced, T2 = Fogging, T3 = Whitewashed)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

TDA

T1: V. Forzada

250

T2: Nebulización

200

T3: Blanqueo

150 100

NS NS

0 0

Lavado del blanqueo (58 ddt)

100

150

200

250

Días después del transplante

Chart 12: Number of Thrips acquired daily (TDA on graph) for a pepper crop under three systems of cooling (T1 = Forced, T2 = Fogging, T3 = Whitewashed)

In post-test runs the influence of two cooling strategies on the incidence of pests (B. tabaci y F. occidentalis) and on TSWV was evaluated (whitewash by standard dosage, versus fogging) on a greenhouse crop of California peppers. The fact that fogging adjusted the humidity deficit and eased the water stress during the early weeks, favoured the development and reproduction of thrips, which maintained levels higher than for whitewashing (Gázquez et al., 2007). The differences found in the presence of thrips also obtained for a major incidence of TSWV under fogging, with 72 % of plants affected in the final growing cycle. December was the month with the highest incidence of sick plants (more than 30 % of the total). With whitewashing, not even 5 % of plants were infected (chart 13) (Gázquez et al., 2009a). 80 T:1 Blanqueo

72 % 70

30 T2: Nebulización + Blanqueo

% TSWV

25 20

T:1 Blanqueo Acumulada

T2: Nebulización + Blanqueo Acumulada

20 4%

5 0

% TSWV Acumulado

10 0

AGOSTO SEPTIEMBRE OCTUBRE NOVIEMBRE DICIEMBRE

ENERO

MESES

Chart 13: Pattern of percentage (TSWV Virus) in a pepper crop under cooling techniques (whitewashing with standard dosage and fogging, plus whitewashing with a 50 % reduced dosage)

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management The results will show that the fogging strategy combined with whitewashing the cover (whitewash dosage: 12.5 kg of Spanish White per 100 litres of water) significantly increases the populations of Frankliniella occidentalis as compared with the standard dosage (25 kg of Spanish white per 100 litres of water). (Chart 14 & 15) With regard to viruses transmitted by thrips, again there was a major incidence of TSWV under this regime, the difference being that no change was observed in the incidence of Bemisia tabaci (Gázquez et al., 2009a).

Moscas Día Acumuladas

NS NS NS

NS NS

1800 1500 1200 900 600

Lavado blanqueo (ddt 76)

300 0 0

100

125

150

175

Días después del transplante

Chart 14: Pattern of flies acquired per day on the plant for a pepper crop under two cooling strategies: whitewashing with standard dosage and fogging, plus whitewashing with dosage reduced by 50 %

Trips Día Acumulados

1000 900 800 700 600 500 400 300 200 100 0

Lavado blanqueo (ddt 76)

100

125

150

175

Días después del transplante

Chart 15: Pattern of thrips acquired per day on a plant for a pepper crop under two cooling strategies: whitewashing with standard dosage and fogging, plus whitewashing with dosage reduced by 50 %

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management

References Antignus, Y.; Lapidot, M and Cohen S. 1999. UV-Absorbing Plastic Films and Nets - An Innovative Tool of IPM to Reduce the Spread of Insect Pests and Virus Diseases in Covered Crops. Phytoparasitica 27:1, 1999: 76-77 Antignus, Y.; Nestel, D.; Cohen, S.; Lapidot M. 2001. Ultraviolet-deficient greenhouse environment affects whitefly atracction and flight-behavior. Environ. Entom.. 30: 394-399. Aroca, R. 2003. Ensayo de un sistema de refrigeración evaporativa en un invernadero multitúnel. Proyecto fin de carrera. 147 pp. Universidad de Almeria. Baker, J.R. and Shearin, B.A. 1994. An update on screening for the exclusion of insect pests. N. C. Flower Growers' Bull. 39(2): 6-11 Bartzanas, T.; Boulard, T. and Kittas, C. 2002. Numerical simulation of the airflow and temperature distribution in a tunnel greenhouse equipped with insect-proof screen in the openings. Computers and Electronics in Agriculture. 34(1-3): 207-221 Bell, M.L. 1997. Select insect screens on their exclusion capability. Greenhouse Manag. Prod. 29-31. Bell, M. and Baker, J.R. 1997. Select greenhouse screening materials for their ability to exclude insect pests. N. C. Flower Growers' Bulletin. 42(2): 7-13. Bell, M. and Weatherley, N. 1999. Greenhouse insect screens - making the right selection. The Nursery Papers. Bertholf, L.M., 1931. The distribution of stimulative efficiency in the ultra-violet spectrum for the honeybee. J. Agr. Res., 43: 703-713. Bethke, J.A., Redak, R.A. and Paine, T.D., 1994. Screens deny specific pests entry to greenhouses. California Agric., May-June, 37-40. Brown, P.E.; Frank, C.P.; Groves, H.L.; Anderson, M., 1998. Spectral sensitivity and visual conditioning in the parasitoid wasp Trybliographa rapae (hym.: Cynipidae). Bulletin of Entomological Research, 88: 239245. Critten, D.L. and Bailey, B.J. 2002. A review of greenhouse engineering developments during the 1990s. Agricultural and Forest Meteorology. 112: 1-22. Cabello, T.; Van Der Blom, J.; Soler, A., 2005 a. Efectos de los plásticos antiplagas sobre los insectos polinizadores en invernadero. Vida Rural, 219: 40-42. Cabello, T.; Van Der Blom, J; Soler, A., 2005 b. Luz ultravioleta, plásticos y visión en insectos. Actas IV Congreso Nacional de Entomología Aplicada. Bragança: 226. Cabello, T.; Van Der Blom, J.; Soler, A.; Lopez, J.C., 2006. Atractivos florales visuales en plantas hortícolas. II Jornadas de Polinización en Plantas Hortícolas. Junta de Andalucía (Spain): 37-48. Cabrera, F.J.; López, J.C.; Baeza, E. y Pérez-Parra, J. 2002. Informe sobre caracterización de mallas antiinsecto. Almeria Agrícola. 47: 18-27

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management Cabrera, F.J., López, J.C., Baeza, E. and Pérez-Parra, J. 2006. Efficiency of Anti-Insect Screens placed in the Vents of Almeria. Greenhouses. Symposium on Greenhouse Cooling: methods, technologies and plant response. Almeria, April 2006. Chittka, L.; Thomson, J.D., 2001.Cognitive Ecology of Pollination - Animal Behavior and Floral Evolution. Cambridge University Press, 423pp. Díaz Pérez, M.; Gallardo Villanueva, D.; Carmona Medina, J.J.; Camacho Ferre, F. and Fernández Rodríguez, E.J. 2003. Utilización de mallas anti-insectos como protección de invernaderos mediterráneos. In: Innovaciones tecnológicas en cultivos de invernadero. Ed. E.J. Fernández Rodríguez. Ediciones Agrotécnicas. S.L. Madrid. 165-175 Díaz, T., Espí, E., Fontecha, A., Jiménez, J.C., López, J., Salmerón, A. 2001. Los filmes plásticos en la agricultura agrícola. Ed. Repsol. Mundi-Prensa. Madrid Dyer, G. and Chitta, L. 2004. Bumblebee search time without ultraviolet light. J. Exp. Biol., 207: 16831699 Fatnassi, H., Boulard, T., Demrati, H., Bouirden, L. and Sappe, G. 2002. Ventilation performance of a large Canarian-type greenhouse equipped with insect-proof nets. Biosystems Engineering, 82(1), 97-105. Fatnassi, H., Boulard, T., Poncet, C. and Chave, M. 2006. Optimisation of greenhouse insect screening with computational fluid dynamics. Biosystems Engineering, 93, 301-312. Gázquez, J.C., Lorenzo, P., Sánchez, M.C., López, J.C., Baeza, E. and Pérez.Parra, J. 2006. Bioproductivity response to different methods of greenhouse cooling in a sweet pepper crop. Symposium on Greenhouse Cooling: methods, technologies and plant response, Almeria, April 2006. Gázquez, J.C.; Sáez, M.; López, J.C.; Pérez-Parra, J. y Baeza, E. 2007. Influencia de tres sistemas de refrigeración en la presencia de plagas y en enfermedades en un cultivo de pimiento California. XI Congreso Nacional de Ciencias Hortícolas (SECH). Albacete. Gázquez, J.C.; López, J.C; Baeza, E; Pérez-Parra, J, Meca. D, Parra, A. 2009a. Influencia de dos estrategias de refrigeración en la presencia de plagas y virus del bronceado del tomate en un cultivo de pimiento California en invernadero. VI Congreso Ibérico de Ciencias Hortícolas (SECH). Logroño. Acta de horticultura, 54: 220-221 Gázquez, J.C.; López, J.C.; Baeza, E; Pérez-Parra, J.; Pérez, C; Meca, D, Acosta, J.A., 2009b. Screenhouses on the Mediterranean Basin: Pest Incidence and Productivity of a Tomato Crop. GreenSys 2009. Québec, (Canadá), Junio 2009. Gonzalez, A., Rodríguez, R., Bañon, S., Franco, J.A, Fernandez, J.A., Salmeron, A. y Espí, E. 2003. Strawberry and cucumber cultivation under fluorescent photoselective plastic films cover. Acta Horticulturae, 614:407-414. González, F. 2008. Transpiración de un cultivo de pimiento california bajo distintos niveles de radiación y déficit de presión de vapor. Proyecto fin de carrera. Universidad de Almeria González-Real, M.M. and Baille, A. 2006. Plant response to greenhouse cooling. Proceedings of the international symposium on greenhouse cooling. Acta Horticulturae, 719: 427-437

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management Hanafí, A.; Bouharroud, R.; Miftah, S. and Amouat, S. 2003. Evaluation of different types of insect screens for the exclusion of whiteflies and natural enemies. IOBC/WPRS Bulletin. 26(10): 43-48 Hand, D. W. 1984. Crop responses to winter and summer CO2 enrichment. Acta Horticulturae, 162: 4564. Hollingsworth, J.P.; Hartstack, A.W.; Lingren, P.D., 1970. The spectral response of Campoletis perdistinctus. J. Econ. Entom., 63:1758-1761. Jaffrin, A.; Makhlonf, S. (1990). Mechanism of light transmision through wet polymer Acta Horticulturae, 281: 11-24. Jarvis, W.R., 1997. Control de enfermadades en cultivos de invernadero. Ed. Mundi-Prensa. Madrid Kittas, C., Boulard, T., Bartzanas, T., Katsoulas, N. and Mermier, M. 2002. Influence of an insect screen on greenhouse ventilation. Transactions of the ASAE, 45(4), 1083-1090. Klose, F. and Tantau, H.J., 2004. Test of insect screens- Measurement and evaluation of the air permeability and light transmission. Europ. J. Hort. Sci., 69 235-243. Kittas , C., Boulard, T., Mermier, M., Papadakis, G., 1996. Wind Induced Air Exchange Rates in a Greenhouse Tunnel with Continuous Side Openings. J Agric. Eng. Res. 65 (1), 37-49. Lapidot, M.; Cohen, S.; Antignus, Y 2002. Interferencia de la visión UV de los insectos: una herramienta IPM para impedir las epidemias de las plagas de insectos y las enfermedades virales asociadas con los insectos. Phytoma-España.135:172-176. Lorenzo, P.; Maroto, C.; Castilla, N. 1990. CO2 in plastic greenhouse in Almeria (Spain). Acta Horticulturae, 268: 165-169. López, J. C., Pérez, C., Soler, A., Pérez-Parra J., Gázquez J. C., Meca, D. y Rodríguez M. A. 2006. Evaluación de tres materiales anti-plagas para cubierta de invernadero. X Jornadas del grupo de horticultura. Granada: 21-25 Maillo, J. 2005. Evaluación de distintos sistemas de refrigeración: Ventilación forzada, Nebulización y Encalado estándar bajo similares estructuras de invernadero multitúnel. Proyecto fin de carrera. 170 pp. Universidad de Almeria. Meca, D.; López, J.C.; Gázquez, J.C.; Baeza, E.; Pérez-Parra, J. 2006. Evolution of two cooling system in Parral type green house with pepper crops: Low pressure fog system verses whitening. Proceedings of the international symposium on greenhouse cooling. Acta Horticulturae, 719: 515-520. Meca, D.; López, J.C.; Gázquez, J.C.; Baeza, E.; Pérez-Parra, J. 2007. Efecto de dos dosis de blanqueo sobre la productividad y el microclima de un cultivo de pimiento en invernadero. XI Congreso Nacional de Ciencias Hortícolas (SECH). Albacete. Meca, D., 2008. Efecto de dos dosis de blanqueo sobre la productividad y el microclima de un cultivo de pimiento en invernadero. Proyecto fin de carrera. Universidad de Almeria Mistriotis, A.; Bot, G.P.A.; Picuno, P; Scarasscia-Mugnozza, G. 1997. Analysis of the efficiency of greenhouse ventilation using computational fluid dynamics. Agricultural and Forest Meteorology, 85: 2 17-228.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management Molina-Aiz, F.D., Valera, D.L. and Alvarez, A.J. 2004. Measurement and simulation of climate inside Almeria-type greenhouse using computational fluid dynamics. Agricultural and Forest Meteorology, 125, 33-51. Monci, F., García-Andrés, S. Sánchez, F. Morcones, E., Espi, E, y Salmeron, A. 2004. Tomato yellow leaf curl disease control with UV-blocking plastic covers in comercial plastichouses of Southern Spain. Acta Horticulturae, 633:537-542. Montero, J.I.; Antón A.; Muñoz, P. 1998. Refrigeración de invernaderos. Tecnología de invernaderos II. Curso Superior de Especialización. Eds. Pérez-Parra y Cuadrado. FIAPA, Diputación Provincial de Almeria y Junta de Andalucía, pp. 313-398. Muñoz, P. 1998 Ventilación natural de invernaderos multitúnel. Tesis doctoral. Universitat de Lleida. Munoz, P., Montero, J.I., Anton, A. and Giuffrida, F. 1999. Effect of insect-proof screens and roof openings on greenhouse ventilation. J. agric. Engng. Res., 73, 171-178. Papadakis, G.; Briassoulis, D.; Mugnozza, G.S.; Vox, G.; Feuilloley, P.; Stoffers, J.A. 2000. Radiometric and thermal propertiers of, and testing methods for, greenhouse covering materials. Journal Agricultural Engineering Research, 77 (1):7-38 Parra, A. 2007. Estudio de la influencia de la radiación solar y el déficit de presión de vapor sobre el cultivo de pimiento bajo distintas estrategias de refrigeración. Proyecto fin de carrera. Universidad de Almeria. Pérez-Parra, J.J. 2002. Ventilación natural en invernadero tipo parral. Tesis doctoral. Universidad de Córdoba. Perez-Parra, J., Baeza, E., Lopez, J.C., Perez, C., Montero, J.I. and Anton, A. 2003. Effect of vent types and insect screens on ventilation of "Parral"greenhouses. Acta Horticulturae, 614, 393-400. Perez-Parra, J., Baeza, E., Montero, J.I. and Bailey, B.J. 2004. Natural ventilation of Parral Greenhouses. Biosystems Engineering, 87(3), 355-366. Pérez-Parra, J.; Aroca, R., Zaragoza, G; Baeza, E.; Gázquez J.C.; López, J.C. 2005. Efecto de un sistema de nebulización de alta presión sobre el clima y la bioproductividad de un cultivo de pimiento en invernadero. VI Congreso Ibérico Ciencias Hortícolas (SECH). Oporto. Volumen I. Pag. 315-321. Pérez, C., López, J. C., Gázquez, J. C., Meca, D. E., Marín, A., Bermúdez, M. S.; Soler, A. 2007. Influencia de los plásticos antiplagas sobre los polinizadores naturales de los cultivos hortícolas en invernadero. XXXVII Seminario de Técnicos y Especialistas en Horticultura. Almeria. Pérez, C.; López, J.C.; Gázquez, J.C.; Marín, A.; Bermúdez, M.S., 2009. Experiencias con plásticos antiplagas en cultivos de tomate y sandía. VI Congreso Ibérico de Ciencia s Hortícolas (SECH). Logroño. Acta de horticultura, 54: 204-205 Rapisarda, C.; Tropea, G.; Cascote, G.; Mazzarella, R.; Colombo, A.; Serges, T., 2006. UV-absorbing plastic films for the control of Bemisia tabaci (Gennadius) and Tomato Yellow Leaf Curl Disease (TYLCD) in protected cultivations in Sicily (South Italy). Proceedings of the international symposium on greenhouse cooling. Acta Horticulturae, 719: 597-604.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse technology & integrated pest management Rodríguez, E., 2006. Determinación de la transpiración de un cultivo de pimiento bajo tres sistemas de refrigeración: ventilación forzada, nebulización y blanqueo. Proyecto fin de carrera. Universidad de Almeria. Ross, D.S. and Gill, S.A. 1994. Insect Screening for Greenhouses. Maryland Cooperative Extension. University of Maryland. 21 pp. Sáez, M.I. 2005. Refrigeración de invernaderos mediante ventilación forzada y nebulización: efecto sobre clima y producción. Proyecto fin de carrera. 129 pp. Universidad de Almeria. Soler, A.; Van Der Blom, J. y Cabello, T. 2005. Efecto de cubiertos de invernadero UV absorbentes en el comportamiento de polinizadores (Bombus terrestris y Apis mellifera: Hymenoptera, apidae) en condiciones de bio-ensayo. Actas IV Congreso Nacional de Entomología Aplicada. Bragança: 93. Salmerón, A., Espí, E., Fontecha, A.; García-Alonso, Y., 2001. Fílmes agrícolas avanzados: un campo abierto. Actas I Simposio internacional de Plasticultura. Teitel, M.; Barak, M.; Berlinger, M.J. and Lebiush-Mordechi, S. 2000. Insect-proof screens: Their efect on roof ventilation and insect penetration. Acta Horticulturae. 507: 25-34. Teitel, M., 2001. The effect of insect-proof screens in roof openings on greenhouse microclimate. Agric. Forest Meteorol. 110, 13-25. Teitel, M., 2006. The efeect of sreens on the microclimate of greenhouses and screenhouses - a review. Proceedings of the international symposium on greenhouse cooling. Acta Horticulturae, 719: 575-586. Varela, F., 1974. Los ojos de los insectos. Editorial Alhambra. Bilbao: 108 pp. Valera, D.L.; Peña, A.; Molina, F.D.; Álvarez, A.J.; López, J.A. and Madueño, A. 2003. Caracterización geométrica y mecánica de diferentes tipos de agro-textiles utilizados en invernaderos. Resumen 2⁰ Congreso Nacional de Agroingeniería. 267-268. Weiss, H.B., 1943. Color perception in Insect. J. Econ. Entom., 36:1-17.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Soil cultivation: Characteristics, correction and disinfection Antonio José Céspedes López Cajamar Research Centre ‘Las Palmerillas’

Soil

Soil is the outer layer of the Earth’s crust, the medium in which roots develop and from which they extract the water and nutrients that the plant needs, and which also provides them with support. In a soil profile, there are usually three discernible layers or horizons:  



Horizon A is the actual soil of the uppermost layer, where most of the roots are to be found and it is the richest in nutrients and organic matter Horizon B, or the subsoil, is where the deeper roots are to be found. It has a low level of organic matter and can be enriched with salts and nutrients passed down from the upper layer Horizon C is the bedrock, made up of mainly broken down rock, which forms the deepest layer

1.1 Soil fertility It is the capacity of the soil to supply each and every one of the nutrients in the right way, in the right amount and at the right time to meet the demands of the crop. The first step is to analyse the soil to be used for cultivation. This analysis enables us to plan the best soil management strategy for cultivation.

1.2 Soil sampling The most critical point for soil analysis is that the sample taken be the most representative of the soil. To collect the sample the following steps must be followed:  

 

The sample should be taken after harvesting and before fertilisers are used To detect homogeneous areas within the plot samples representing each of them must be taken, without mixing the different areas, so as to be able to understand the homogeneity Samples are to be taken in different places in each homogeneous zone in the plot, following a “ziz-zag” pattern through each one The first two centimetres of the surface soil must be discarded and the sample shall be taken from the 2 to 20 cm of soil (irrigated herbaceous crops). In plots with drip-

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection



  

irrigation, the sample is to be taken from the moist area around the dripper. The number of sub-samples per homogeneous zone will be between 10 and 15 samples. The different layers or horizons should not be mixed. If different horizons can be seen in the sample-site, the horizon A sample is to be removed. If different horizons are to be analysed, the samples are to be taken from each one and the samples from the same horizons are to be mixed Remove between 1 kg and 2 kg from the thoroughly mixed samples which will then be sent to the laboratory Galvanised or bronze tools should not be used if samples are to be analysed for micronutrients such as zinc or copper The samples should not be exposed to high temperatures or left in the sun. They are to be sent to the laboratory as soon as possible

The main factors to be determined are: Texture, pH, electrical conductivity, organic matter, carbonates, cationic exchange capacity, the base saturation percentage and the available phosphorous and potassium. The first point of contact with our soil should be through complete and exhaustive analysis of same, opting for an annual basic analysis at the very least, so as to monitor and carry out necessary adjustments.

1.3 The optimum soil Medium textured soil; silt loam, loam, sandy clay loam, silty clay loam and clay loam textures. These soils are slightly sticky and plastic when wet, soft to firm when moist, slightly hard when dry. They have a high proportion of small to medium sized pores, a moderately high water and nutrient retention capacity and tend to form small to medium size aggregates.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Graph 1: Textural USDA diagram pH: Associated with the availability of nutrients. The ideal pH is between 6.5 and 7.5

Graph 2: Availability of nutrients depending on the pH and optimum pH range

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Electrical Conductivity (EC): It should ideally be below 4 dS m-1. Above 4 dS m-1, the soil is considered saline. Organic Matter (OM): This is important due to the way it enhances a soil’s physical properties (structure, aeration), it increases the cation-exchange capacity (CEC) and biological activity in the soil. In ideal conditions we would aspire to a level of 2 % organic matter in the soil. Carbon-to-nitrogen Ratio (C/N): This should be between 8 and 12. At values below 8 there is a mass release of nitrogen and therefore supply should be reduced. If the ratio is greater than 12, nitrogen release is low and nitrogen supply should be increased. Carbonates: These play an important role in the structure of the soil. The ideal level is below 15 %. When readings are higher an active lime assessment should be carried out. Values above 20 % indicate soil with high calcium content, check for possible P fixation problems and assume there is low availability of Fe, Zn, Mn or Cu. The level of these micronutrients should be tested using the DTPA method. In these soils acidic reaction fertilizer are recommended to minimize the effect of high concentrations of carbonates. Cation-Exchange Capacity (CEC): This is heavily dependent on the content of clay and OM of the soil, the more clay and OM there is, the higher the CEC. This is the soil’s capacity to retain cations and is measured in meq/100 g. Normal values are between 10 and 20 meq /100 g, values below 5meq / 100 g indicate low OM content which leads to poor soil fertility. Conversely, values close to 30 meq / 100 g indicate soil that is excessively clayey. Percent base saturation: This refers to the percentage of major cations with regard to the total CEC value, i.e. the proportion in which the different cations are present in the exchange complex. The ideal distribution would be as follows: CATION

% of CEC

Calcium

60 - 80 %

Magnesium

10 - 20 %

Potassium

2-6%

Sodium

0-3%

Available phosphorous: Contents from 30 ppm to 45 ppm, in soils of medium texture and use in irrigation (Olsen Method). Available potassium: Contents from 140 to 220 ppm.

1.4 Possible soil problems The main problem with irrigated soils is salination. The accumulation of soluble salts in the root zone of the crops initially produces a decline in performance, it can affect the soil structure (Na) and problems of toxicity (Na,Cl and B) can arise. The key tools to control

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection salination are drainage and irrigation. The three scenarios that may occur are listed in the following table. PROBLEM

Saline Soils

INDICATIONS

SOLUTION

pH < 8.5

∙ They can be recovered through washing, preferably flood irrigation, if the water quality is good and there are no drainage problems. If water quality is not good, it will be necessary to increase the quantity of water so as to leach out the excess salts and prevent soil salinity. ∙ Solution: Washing

CEes > 4dSm-1 PSI < 15 %

∙ These have similar properties to the saline soils and, owing to the excess of salts, the particles remain Saline-sodium flocculated. If washed only with water they become CEes > 4dSm-1 non-saline, sodic soils. This implies that the increase of the pH to levels above 8.5 increases the PSI and the Soils particles in the soil are dispersed, thus reducing PSI > 15 % infiltration. If there is no gypsum in the soil it will need liming before it is washed. ∙ Owing to the high sodium content there is a substantial pH > 8.5 dispersion of clay and organic matter that reduces drainage. To regenerate them, drainage must be Sodic Soils CEes < 4dSm-1 improved calcium or acidic amendments added if the soil contains lime, and then washing it. PSI > 10 - 15 % ∙ Agricultural gypsum is used to amend soil that is lacking in calcium and sulphur in soils which are rich in calcium. Whatever the case, it is worthwhile to consult a technical advisor about the problem in order to trace the origin of same and to adopt the most suitable strategy. pH < 8.5

Table 2: Possible soil problems

1.5 Soil preparation The most widespread growing medium in Almeria is soil. In the eighties the first substrate crops were introduced, but the idea did not take off until the beginning of the nineties. In the survey carried out in the 2005/2006 season the area of greenhouses with crops in substrate reached 20.4 %, the rest of the crops are mainly grown in greatly modified soil.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection % Greenhouse area 2005/2006 Survey

“Enarenado”

Added sand

Added soil

Original soil

Graph 3: Distribution of soil preparation systems in the greenhouses of Almeria. Survey 2005/2006

One modification that characterises the horticultural production in Almeria is the use of sand as mulch. This protective layer is used in almost 60 % of the growing surface in soil and is called; “enarenado” or sanded soil.

1.6 “Enarenado” or sanded soil Sand was already used as mulch protection for crops prior to the establishment of greenhouses. In the fifties, with the colonisation of the “Poniente’ or western region of Almeria, trials were carried out in the Roquetas de Mar - El Parador area (in 1957). The aim of these was to study the behaviour of different horticultural species, varieties and cycles, and also the possibilities that the sanded-soil technique could provide for the new form of agriculture developing in the region. This technique provided a series of advantages and qualities that made it attractive for horticultural development.

1.7 The basis of soil sanding Rapid heating of soil With this system soil heats up more during the day and there is lower heat loss during the night. These effects are produced by the low heat capacity of the protective layer (sand, mainly quartz particles) and its poor capacity for water retention. These two factors in conjunction mean that the protective layer heats up more quickly, and to a greater degree, during the day. This heat moves, via conduction, to the lower nutritive and impermeable horizons, where it is stored even though the sand may become cool. Therefore, increases in temperature of more than 10 ⁰C can be observed, compared to land that has not been improved in this way.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Moreover, during the night there is less heat loss from the soil (the sand acts as an insulator) and the plants are not subjected to such severe diurnal and nocturnal thermal variations, as occurs in soils that have not been improved with the soil-sanding system. The temperature around the plants also increases owing to the solar radiation reflected off the sand, which stimulates photosynthesis and favours growth and crop development. These increases in temperature are a positive influence on the early development of the crops. Structural maintenance Sand plays an important role in protecting the soil against external actions such as workers’ footsteps, the ruts of the trolleys and agricultural machinery, maintaining the structure in the same conditions of aeration and initial water retention ability. The layer of sand also prevents the soil from cracking, so harmful and common in saline and clay soils, eliminating both the possible evaporation of moisture through the cracks as well as the accumulation of salts on the surface. The enhancement of microbial activity in the soil The increase of ground temperature, the reduction of temperature variation, the adding of large quantities of organic matter, the achievement of the appropriate level of moisture, the reduction in pH and the decrease in soil salinity; all of these factors have a positive influence on the activation of microbial life of the soil, its fertility and the solubilisation of the salts. Decreasing soil salinity In clay and saline soil, as is generally the case in the “enarenado” area, the effect occurring after each irrigation is an ascending movement of water due to capillarity, from the subsurface horizons which provide moisture to the higher layers as these dry out. In these areas this phenomena is particularly intense because of the high temperatures and frequent winds. When this evaporation takes place, the salts that had been dissolved in the water through land washing, and those that were carried from the aquifers, accumulate in the soil. Due to successive irrigation, a surface layer with such a high concentration of mineral salts forms, the osmotic pressure impedes the absorption by the plant’s roots of nutrients from the soil, thus rendering plant vegetation impossible. By breaking the capillarity the protective layer reduces evaporation to about 30 % or lower, compared to the norm. In this way, the upper level remains damp and the dangerous concentration of salts does not occur. Irrigation and rain water penetrate downwards, with which the mineral salts are leached to the lower levels. Conversely, there is a notable production of carbon dioxide because of the intense microbial activity in the abundant manure and a high C/N ratio, which acts favourably on the solubilisation of salts.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Reduction of evaporation The protective layer breaks the capillary rise of the water in the land, impeding or enormously reducing the substantial evaporation of water from the soil. Consequently, apart from the saving of water in an area where it is both scarce and expensive, the soil sanding growing system contributes to the regulation of soil temperature and to keeping the concentration of salts lower, uniform and stable, in the nutritive and in the protective horizons, where most of the root systems develop. Condensation of atmospheric humidity If the sand heats up on the surface more rapidly than the soil during the day, it also cools down faster at night. This produces condensation of atmospheric humidity that helps to maintain the required degree of humidity and to avoid harmful drops in temperature. Difference in plant root system development With the soil-sanding growing system root development is very different. Crop observation shows us that the plant roots, even powerful root systems, barely enter the impermeable horizon (clay soil). When a rootball is transplanted, it is placed into a hole, made using a borer or a planting hoe, in the impermeable horizon. In this case the root goes a bit deeper but quickly develops the side roots that are the most efficient ones. In tomato growing it is common practice to carry out “sinking”, which consists of burying up 15 to 20 cm of the lower part of the stem in earth in order to increase the rhizosphere. As a consequence, root development is centred mainly in the manure area, the lower area of the sand and the upper layer of the soil; areas that, on the other hand, desalinate quickly and reach higher temperatures. For this reason, they can also be grown in poor quality soil, obtaining earlier and more abundant crops. This soil is not an accumulator of water and nutrients as would normally be the case. Its function is basically physical; to impede the vertical movement of water as much as possible, both upwards and downwards. What is imperative is to provide this horizon with sufficient slope for excess water to be removed.

1.8 Carrying out the soil-sanding process In the first place the earth must be broken up and necessary steps taken to guarantee good drainage of the plot, sub-soiling, laying of drains, trenches filled with boulders etc. When these preparatory tasks have been fulfilled the original soil should be broken up and levelled. The levelling is carried out creating terraces with gradual 2:1.000 or 3:1.000 longitudinal slope and a 0.5:1.000 transverse slope. It is recommendable that the surface of the terrace be exposed at midday; that is to say, that the lowest part faces to the south of the plot and the highest to the north.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Figure 1: Ideal orientation and slopes for the terracing

A layer of 20 to 30 cm of lime-clay, silty-loam soil, free from large objects, is spread evenly over the levelled plot. The addition of “good quality” soil should only be necessary when the quantity or quality of available soil, or its physicochemical properties, on the plot to be transformed are not adequate for the crops to be grown on it. New soil is not needed in the case of previously cultivated, or newly prepared, plots with satisfactory lay, drainage and fertility. The work prior to carrying out the soil-sanding process should be capitalised to carry out any soil correction seen to be necessary following the chemical analysis, especially improvements or corrections that require in-depth localisation.

SAND (10 – 12 cm) MANURE (1 - 2 cm) 80 t

SOIL (30 cm)

SUBSOIL

Figure 2: Layout of “enarenado” or sanded soil

Once the plot has been levelled, whether soil has been added or not, comes the spreading of some 40 t ha-1 of manure which will be well dug in; For this layer it is better for the manure to be full of fibre with a long texture and half fermented as the objective is to improve the soil physically.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection After these tasks the land will be smoothed and levelled to achieve the required slopes, leaving the soil ready for another layer of manure, this time finer and approximately two centimetres deep which should be spread evenly. The most appropriate for this layer is sheep manure with “bedding”, which should not be powdery. The quantity to be used for this second layer is another 40 t ha-1. The European Union, with the aim of reducing the incidence of contamination through nitrates from agricultural sources, approved the Directive 91/676/CE which was incorporated into Spanish legislation through Real Decreto (Royal Decree) 261/1996 16th of February regarding the protection of water against contamination produced by nitrates from agricultural sources. La Comunidad Autónoma de Andalucía (the Autonomous Community of Andalusia) through Decreto 261/1998 proceeded to designate areas vulnerable to nitrate contamination from agricultural sources in Andalusia. The Order of 18th November 2008 approved the programme of action applicable for vulnerable areas. This programme limits the addition of manure (Group 1 fertilisers) per hectare to the amount that contains a maximum of 170 Fertilising Units of Nitrogen (170 Kg of Nitrogen). The addition of sand is made by depositing conveniently spaced loads of sand and calculating an average depth for spreading of some 10 centimetres (10m³ per 100m²). The spreading can be done by hand if the distances are short or by an articulated power-tiller with front or rear shovel. Care must be taken with the route of the vehicles transporting the sand and manure within the plot of land, to keep compacted ruts caused to a minimum. Once there is no need to go over a track again it should be ploughed or rotavated, should the necessary equipment be available, and levelled before covering it with the layer of manure and sand respectively. This will avoid the compaction that will cause water-logging and hinder the root development of the crop. Once the sand has been spread the area should be irrigated. This should be done using flood irrigation, never drip, as the entire contour of the plot must be completely wetted in a uniform fashion, using a great volume of water and taking advantage to chemically disinfect the land.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Figure 3: Breaking up and de-stoning

Figure 4: Levelling of the land

Figure 5: Heaps of additional earth

Figure 6: Spreading and levelling of the additional earth

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Figure 7: Heaps of manure for spreading

Figure 8: Spreading of manure

Figure 9: Adding of chemical fertilisers

Figure 10: Rotavation to blend the manure, fertiliser and additional soil

Figure 11: Second layer of manure and piles of sand

Figure 12: Sand once spread

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

1.9 Chracteristics of sand to be used Aggregate quarrying is currently prohibited along the whole of Spain’s coastline. Nowadays, the only sand that can be used is from quarries or pockets of river or marine sand from areas not within the limits defined in the Law of Coasts. There must always be a favourable environmental impact report regarding the extraction. The ideal grain size of sand for agricultural use is between 2 and 5 mm in diameter. The smaller the size of the sand grain, the smaller the pores between the grains. This helps increase capillary action and consequently favours the evaporation of the rising water which leads to the cooling down of the underlying soil, including the area surrounding the crop root system. This also conditions the precocity of the crop. Sand from crushing plants is not suitable for agricultural use, not only due to its higher cost but also because its sharp edges can damage the stems of the plants as they increase in size, move in the wind, in the course of agricultural tasks, harvesting etc. The chemical composition of the sand used in agriculture tends to contain a high percentage of silica (quartz and quartzite) followed by carbonates and metamorphic clay (slate). The chemical activity of these types of sand is limited.

1.10 “Enarenado” Soil-sanding operation The sowing or planting that is to take place in the plots prepared in this way requires the use of very specific or special tools and work patterns. Therefore, for the planting of any seed such as beans, melons, watermelons, courgettes or cucumbers, prior irrigation is needed to prepare the soil for germination and the emergence of the seedling. This can be carried out by using a localised irrigation network or by flooding, cordoning off the sand so as to save water and directing it only to the rows that are to be planted.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Sowing is carried out the following day, in the case of cucurbits, with pre-germinated seeds or without for other types. The sand should be parted, using a suitable tool, so as to deposit the seed onto the original soil or the additional soil, in the required position. This should then be covered with the original sand that was removed. Irrigation should not be repeated until all the seeds have emerged. When planting seedlings from nurseries, in a plug of substrate peat mixture, this is carried out after a pre-planting irrigation by parting the sand at the point where the seedling is to be placed. Afterwards, the earth is marked with a rod ending in an inverted pyramid of the same shape and size as the plug in which the seedling has been grown. The plug is then placed in the hole, replacing the sand removed previously and then watering to ensure that there is the greatest contact between the seedling plug and the soil. The soil-sanding process is a semi-permanent improvement. This is due to the fact that it is necessary to replenish the supply of manure, or “retranquear” every so often. The interval between the sanding process and the replacement of organic matter, which tends to be every three or four years, varies according to the number of harvests and the rotation, or succession, of crops that have been grown, above all if they have been high-performance crops such as tomatoes, peppers or aubergines etc. To replenish manure it is important to leave a certain time between the end of the previous crop before pulling up the plants. This is to allow the transpiration of the plants to deplete the soil of its activity. Once this time has passed the crop is grubbed up and the greenhouse vegetable waste removed. The sand is then cleaned, raked back and banked up, leaving the subsoil uncovered. The banking up of the sand is carried out using the same hand tools or machinery, previously mentioned in the soil-sanding process, leaving alternating “tracks” with and without sand, which will be tilled, manured and once again rotavated into the topsoil, in the same quantities used at the initial process, spreading it out one strip after another and finally irrigating to settle it. After the second re-manuring of a sanded plot, it will be necessary to replace a certain quantity of sand that may have been lost through mixing with the supporting soil, during cultivation and re-manuring tasks. An important factor is the marked differences in the decrease of water infiltration rates and the characterisation of the root system distribution in a tomato crop in soil that has been remanured and soil that has not. Castilla (1986) obtained the following values in relation to the infiltration rate, measured with double Muntz ring at the Cajamar Research Centre ‘Las Palmerillas’:

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection INFILTRATION RATE (cm h-1) Re-manuerd soil

8.28 (A)

Non-remanured soil

0.38 (B)

A/B relation

21.79

The A/B shows us the extremely high proportion and quantity of water that soil that has been re-manured is able to absorb compared to the soil that has not. The “retranqueo” or re-manuring is an operation which has fallen into disuse; it has been replaced by “carillas” or small trenches. This consists of tilling and adding the manure along a narrow strip just the same width as the planting row. This tendency is justified by the saving of man-hours and costs.

Figure 13: “Carillas” or strips of approx 1 m width are opened

Figure 14: The organic matter is spread

Figure 15: Fertilisers are spread

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Figure 16: A corrector or amendment is added

Figure 17: Rotavation to blend everything in

Figure 18: Trench is closed and irrigated

Soil disinfection

Soil disinfection is a widespread cultural practice, necessary above all when monoculture is carried out season after season. A producer tends to specialise in certain crops, achieving improved productivity and quality but also accelerating soil fatigue or depletion, making soil disinfection even more necessary.

Traditionally, the use of fumigants for soil disinfection was widespread and amongst these Methyl Bromide (MB) stood out both for its effectiveness but also for its level of danger. Owing to its negative effect on the ozone layer, in 1992, it was registered as an ozone-depleting substance (ODS) in the Montreal Protocol. In 1995 in Vienna, a schedule for the suppression of MB use was agreed on, from the 1st January, 2005 in the case of developed countries (Countries Art.2) and 1st January, 2015 for developing countries (Countries Art 5). Different formulations of 1.3 dichloropropene together with chloropicrin have taken over. Running parallel to this chemical option there is the alternative, more environmentally friendly option, with no residue problems, in which heat is used for the disinfection of the soil. Firstly steam is injected and then solar radiation is used. This technique is called solarisation, and was developed by Katan in 1976 in Israel. In the 1999/2000 season, the Cajamar Research Centre ‘Las Palmerillas’ at the request of FIAPA (the Foundation for Agricultural Research in the Province of Almeria) surveyed 461 producers to characterise the protected (under plastic) production system. Six years later in the 2005/2006 season a new survey was carried out, this time with 445 producers. The results

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection were as follows; around 90 % of the producers were carrying out disinfection of the crop media (1999/2000 season 89.4 % and in 2005/2006 91.7 %). The active ingredients used in the disinfection of the growing media are shown in the following tables.

Dichloropropene Metam- Sodium Methyl Bromide Metam Potassium Sodium Tetrathiocarbonate

Producers Graph 4: Active ingredients used in the disinfection of cultivation media. 1999/2000 Season

Dichloropropene Metam Sodium Sodium Hypochlorite Metam Potassium Others

PRODUCERS Graph 5: Active ingredients used in the disinfection of cultivation medium. 2005/2006 Season

The application of fumigants is carried out during irrigation, using a substantial quantity of water to soak the greatest possible volume of soil, except with Methyl Bromide which,

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection because of its riskiness, is applied sealing the land with Virtually Impermeable Film (VIF) after application. In this technique the role of the plastic is to act as a barrier to prevent fumes from escaping and thus improve the efficiency of the treatment. The use of plastic with the other fumigants subsequently became more widespread to improve the efficiency using a lower product dose. The following table shows the systems used in the 2005/2006 season.

Chemical disinfection

Mixed Solarisation

Pure Solarisation

23.5 %

6.9 %

1.8 %

51.5 %

7.8 %

Mixed Solarisation Pure Solarisation

8.3 %

Combinations of the different soil or growing media disinfection systems

83.3 % of the producers use, preferably, a single disinfection system for soil, the most widespread being mixed solarisation with 51.5 % of the producers, followed by 23.5 % who use a chemical disinfectant. Only 8.3 % of the producers trust in the sole use of water and use pure solarisation. 16.5 % of the producers tend to combine two systems, 7.8 % use pure and mixed solarisation and 6.9 % use mixed solarisation and chemical disinfection. Lastly, 0.2 % of the producers use all three systems. Frequency with which soil disinfection is carried out The average value stands at around 1.5, that is to say that disinfection is carried out every one and a half seasons.

Each season

Variable (1-4 seasons)

Each 2 seasons

Every 3 seasons

More than 3 seasons

Frequency with which soil disinfection is carried out. 2005/2006 Season

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Current situation The specific regulation for integrated production of protected horticultural crops (Order 10th October, 2007 of the Andalusian Regional Government Ministry of Agriculture and Fisheries establishes the mandatory practice of disinfecting the soil through solarisation and/or biofumigation, with transparent plastic and with the covering completely sealed. Chemical treatments are only to be used in technically justified cases, authorised by the appropriate official body. With the implementation of Directive 91/414/CE specific to agricultural fumigants, (this directive establishes that the agrochemical substances that are not included in a positive list (Annex 1) may not be used), the following active ingredients are amongst those that have been excluded from the annex referred to:   

1.3 Dichloropropene (1.3D) Chloropicrin Sodium Tetrathiocarbonate

Among the fumigants included in the list at the moment are those in the following table Active Ingredient

Toxicology Category

Application System

Dazomet 98 %

XN(AC)

Metam-Na Metam-K

Danger level

SP Days

XXX

Fungicide

Nematicide

Herbicide

Insecticide

Usage

Broadcast incorporation

XXX

B(BB)

Injection Irrigation water

B(BB)

Injection Irrigation

Level of efficiency: X.: Average, XX.: Good, XXX.: V.Good

Danger level: B.: Low, M.: Medium, A.: High. SP=Safety period N/A=Not applicable

Classification of the current available options is as follows: 

Sustainable, environmentally friendly systems ∙



Solarisation, biofumigation, biosolarisation and steam.

Systems based on fumigants ∙

Chemical disinfection and mixed solarisation

2.1 Sustainable, environmentally friendly systems 2.1.1 Steam This is an effective system, if used correctly. Advantage is taken of the disinfecting effect of the damp heat on the living forms in the soil, especially on pathogens. Temperatures of around 80 to 90 ⁰C can often be reached and treatment lasts for at least an hour. The main inconvenience is the cost; it is an expensive system which is not used in Almeria.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection 2.1.2 Solarisation The technique is carried out in the summer. First the land is watered and then covered with a plastic polyethylene sheet of between 25 and 50µ, for a period of between 4 and 6 weeks. In Israel temperatures of 45 to 50 ⁰C at a depth of 10 cm and of 38 to 45 ⁰C at 20 cm have been achieved (Katan,1980). According to studies carried out in the U.S.A. using this procedure, temperatures of 60 ⁰C at 5 cm, 50 ⁰C at 15 cm, 41 ⁰C at 30 cm, etc. were reached in some areas of California (Cenís, 1987). In S.E.Spain with polyethylene lining covered by greenhouse or small tunnel, temperatures exceeded 41 ⁰C at a depth of 30 cm (Martinez et al., 1986). The efficiency of this is improved by combination with chemical (mixed solarisation) or organic products (biosolarisation). The advantages are as follows:    

It is an ecological technique It’s economical Being less drastic it avoids the ecological vacuum It avoids the effects of chemicals on plastic covers

The longer the process lasts, the higher the temperatures that are reached and, the more effective it is. The following table shows the heat sensitivity of some phytopathogenic fungi, under constant laboratory conditions, until 90 % mortality is reached: Fungus

28 ⁰C

31 ⁰C

34 ⁰C

37 ⁰C

40 ⁰C

43 ⁰C

46 ⁰C

50 ⁰C

Verticilium dahliae

+60 d

46 d

11 d

30 h

10 min

Sclerotinia sclerotiorum

30 d

11 d

30 h

1/2 h

5 min

Rhizoctonia solani

27 d

23 d

18 d

14 d

18 h

10 min

Phytophtora solani

+60 d

46 d

41 d

27 d

18 d

36 h

10 min

+60 d

46 d

41 d

35 d

42 h

20 min

+60 d

52 d

41 d

30 d

18 h

10 min

Fusarium oxisporum var gladioli Fusarium oxisporum var gladioli

d: days, h:hours, min: minutes

The aim is, therefore, to reach high temperatures and to then maintain them, in this task the level of humidity is important since the specific heat of the water is greater than that of the air, the soil temperature will be more constant provided that it is kept moist. To be able to maintain these conditions, the sealing of the soil with the plastic must be as hermetic as possible so as to avoid loss of air and moisture. It is not advisable to carry out watering during the solarisation period since this causes extra water consumption and lowers the soil temperature. It is also advisable to keep the greenhouse vents closed. If the plastic cover is nearing the end of its life expectancy it should be changed after carrying out solarisation.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Figure 19: Putting the plastic in place

Figure 20: Solarising a greenhouse

Figure 21: Staple securing the plastic

Solarisation must be carried out coinciding with highest radiation, which in our conditions would be from the middle of June until the end of August (77 days). For the solarisation to be effective temperatures should be kept above 40 ⁰CC. The duration of this would be a minimum of 4 weeks (28 days) although the ideal scenario would be 6 weeks (42 - 45 days).

To carry out solarisation the following steps should be taken:  



 

Wash off the remains of whitewash, dust or dirt from the greenhouse cover Remove weeds, previous crop waste, objects that could pierce the plastic sheet and clods of earth. The soil should be levelled and soft. Where the soil has been sanded, the sand is to be raked to smooth it over and to cover the holes left from the previous crop Irrigate abundantly soaking to a depth of 30 to 40 cm. Flood irrigation is preferable; it can help to wash away the saline deposits from localised irrigation. If localised irrigation is used, it must be carried out in two stages. After the first irrigation the main drip feeder pipe will be moved so as to cover remainder of the plot, the plastic sheeting is put into place and the second irrigation will then take place In non-sanded soils at the time the soil can be stepped on, cover with a transparent plastic sheet of 20 to 50 µm. It should remain in contact with the soil without forming bags of air, perfectly smooth and airtight. The edges the plastic should be secured with deep furrows. It must be taken into account that certain effectiveness is lost in a strip of some 60 cm around the edges Keep the greenhouse closed while solarisation is taking place The plastic is to be kept in place for between 30 and 60 days

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Disadvantages The results obtained in the control of endoparasite root-knot nematodes (Meloidogyne sp) and some weeds and phytopathogenic fungi contained in the deep layers of the soil (Armillaria) are not good.

2.1.3 Biofumigation or biodisinfection In biofumigation the organic matter in agricultural waste and the products of its decomposition are used for the control of plant pathogens originating in the soil. The action of micro-organisms on organic matter produces a great quantity of chemicals amongst which ammonia, nitrates, sulphuric acid and a great number of volatile substances and organic acids, are to be found. Biofumigation has the following advantages:

   

Re-uses agroindustrial waste Low cost Easy application Organic matter is incorporated into the soil

The efficiency of organic amendments for the control of nematodes and other soil pathogens depends on the chemical composition, physical properties and evolution of the soil, which is determined by the type of organisms involved in its decomposition. A substantial quantity, around 50 t haˉ¹, of organic matter is needed. This is one aspect that can be difficult to put in to practice owing to the limitations on the quantity of organic fertilisers per hectare (manure) that contains a maximum of 170 Units of Nitrogen Fertilizer (UNF). To enable the practice, the General Directorate for Agriculture and Livestock issued an order dated 1st June, 2009 in which the maximum quantities of manure/slurry per unit of area in certain areas of Andalusia designated as vulnerable. According to the order referred to, the Andalusian Regional Government Institute for Agricultural and Fisheries Research and Training considered that if the manure (fresh) is used in biofumigation then sealed with plastic (bisolarisation) for 30 days, the microbial flora that develops cause nitrogen losses of up to 40 % which means that the dose may be increased to 66 %.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

Farming Activity Sow in closed cycle Sow with piglets up to weaning (< 6 Kg) Sow with piglets (< 20 Kg) Cull sows Piglets 6 - 20 kg Pig 20 - 50 kg Pig 50 - 100 kg Cereal fed Pig 20 - 100 kg Boars Milking cow Other cows Fattened heifer < 12 months Fattened cattle > 12 months Laying hens, pullets, turkeys Mated goats no births, delivered goats and male goats Young male goats Fattened lambs Mated ewes no births, birthed ewes and ram

N Content 3 of Kg N / m t Manure (Fresh)

N Losses (%) (Biofumigation)

Maximum dose of Manure (t / ha)

Valorisation

Biofumigation

Fresh

Valued

Biofumigation

3.78

0.50

0.40

44.92

89.85

74.87

3.00

0.50

0.40

56.74

113.48

94.57

3.01

0.50

0.40

55.05

110.09

91.75

3.40 4.40 3.51 3.22 3.37 2.60 3.69 3.70

0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50

0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40

50.00 38.72 48.49 52.79 50.41 65.31 46.09 45.90

100.00 77.44 96.99 105.59 100.83 100.48 70.91 70.61

83.33 64.54 80.82 87.99 84.02 108.85 76.82 76.50

6.90

0.50

0.40

24.65

37.92

41.08

4.00

0.50

0.40

42.50

65.38

70.83

9.75

0.50

0.40

17.44

34.87

29.06

5.06

0.50

0.40

33.59

47.98

55.98

4.01 4.00

0.50 0.50

0.40 0.40

42.37 42.50

60.53 60.71

70.61 70.83

4.05

0.50

0.40

42.00

60.00

70.00

The use of plastics in biofumigation is known as biosolarisation and aims to boost the effects of biofumigation and thus reduce the quantity of organic matter or reduce the time that the plastic sheets are kept on with relation to the solarisation. 

Input of organic matter and the task of in-depth digging-in ∙



Alternative organic input  Mixture of manures and nitrogen (ewe manure 4 to 6 kg plus 2 to 4 kg of poultry manure plus 80 g of Urea per square metre)  Commercial preparation  Introduction of crop rotation. A dense sowing of brassicas, rapeseed, turnips, radishes etc, to be cut just before flowering, then shredded with a rotavator, then add 80 to 100 grams per square metre of urea or ammonium sulphate. This is then dug in to a depth of 40 cm rather than 30 cm

Irrigate, thoroughly soaking the whole profile uniformly. With irrigation and the remainder of the procedure (placement of the plastic) continue as with solarisation



INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Disadvantages Bello et al., (2003) state that the greatest problem related with the use of organic amendments is uniformity in the composition of the matter used. Therefore a complete understanding of this is needed so as to avoid the accumulation of compounds that could be harmful and the increase in the levels of inocula of some pathogens.

2.2 Chemical disinfection This has been one of the most frequently used systems because of its ease and effectiveness. As the chemical products used in disinfection turn into gas upon release, covering the soil with sheet plastic to impede the escape of the gases could be an interesting measure. 2.2.1 Considerations for the carrying out of chemical disinfection   

Remove the vegetable waste from the previous crop. The rotting of crop roots is a requirement for good nematicide control. Break up the soil well, avoiding clumps. Maintain a good level of moisture in the soil for the 8-14 days prior to the treatment so as to: ∙ ∙ ∙



Facilitate the decomposition of the vegetable waste and to release the nematodes Favour the germination of the seeds Prevent organisms that cause soil-fatigue developing into a resistant form or state

Do not carry out substantial manuring close to treatment time. The efficiency of the products is reduced when the ammonia reacts with some of the fumigants’ compounds

The product should be applied so to achieve a uniform distribution of same. Mixed disinfection or mixed solarisation. This treatment uses chemical disinfection together with plastic sheeting to increase the effectiveness. The use of plastic also has the following advantages:    

Less disinfectant is lost, thus money is saved Increased efficiency due to reduced product loss and increased soil temperature. The risk of intoxication within the greenhouse is reduced The deterioration of the plastic greenhouse covers, caused by the chemicals, is reduced

For example half of the normal dose of Metam-Sodium can be used and land solarised for 30 to 40 days.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection 2.2.2 Considerations before sowing or transplanting     

Ensure that there are no gas residues remaining in the soil, carrying out aeration at the same time Respect the waiting periods between treating the soil and the crop planting When carrying out aeration, avoid mixing the disinfected layer with the deeper one In sanded soils, given that no aeration operations need to be carried out, increase the waiting period by 50 % To be sure carry out germination test using the seeds of fast growing crops (lettuce, cress etc.)

Fumigants available

3.1 Dazomet The active ingredient is tetrahydro-3, 5-dimethyl-1.3, 5-thiadiazine-2-thione. It is a granulated product which is used as a fungicide, herbicide, insecticide, nematicide and steriliser. Treatment dosage: 350 - 500 Kg ha-1. The product reacts when it comes into contact with moisture in the soil (hydrolysis), insufficient water content can slow down its decomposition and cause the treatment to be less effective and cause phyto-toxicity problems in the crop. Apply to land with at least 50 % humidity of field capacity. If the soil is dry, irrigate between 7 and 14 days before treatment. Do not use during winter or if the soil is excessively moist. Once it has been mixed into the soil, seal the surface to avoid losses of gas through evaporation. Covering with plastic film is recommended to ensure a first-rate treatment result, (be mindful of the gases) losses into the atmosphere are avoided and the product works at a higher temperature. The thickness of the film to be used should be at least 50 micras. It can be mechanically sealed instead, by passing a heavy roller over the surface of the soil and then a thin layer of irrigation is sufficient to seal the suface porosity (5 - 7 L m-²), depending on the type of soil. Give it a light working-over 14 to 28 days after the treatment. If plastic has been used, remove it and leave it open for 5 to 7 days for the soil to air. It’s persistent for between 6 and 8 weeks. Expiry date: 31/05/2015.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

3.2 Metam sodium y Metam potassium) N-potassium methyldithiocarbamate and N- sodium methyldithiocarbamate. These are used fundamentally for the control of root fungi (Fusarium, Verticillium, Pythium, Rhizoctonia, etc.) but they also have a certain herbicide, nematicide and insecticide value. The second is recommended above all, for saline soils so as not to increase the level of sodium. The application dose tends to be 100 kg for each 1.000 m² of commercial product formulated at 50 %, the dosage time should be the same as that of dichloropropene. In this instance there is no need to use a Gotamix or a Venturi as the filters are not damaged by them and they can be pumped in from the fertiliser inlet on the drip irrigation rig. The safety period at normal dosage levels is a minimum of one month.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection

4 Annex. Calculation of the amount of water needed for solarisation. Texture of the soil Sandy Sandy - silt Sandy loam Loose loam Light loam Loam Silty-sandy loam Sandy-clay Silty clay Clay

AHR (mm m-1) 50 - 110 60 - 120 110 - 115 130 - 180 130 - 190 160 - 200 130 - 180 170 - 210 130 - 190 120 - 200

AHR (Available Humidity Range) = Humidity Field CapacityHumidity at wilting point Allen et al., 1998. Pastor, 2005

These values would have to be multiplied by the actual depth of the soil. In sanded soil the depth varies between 0.2 and 0.3 m. However, the quantities that appear in the table are those that would have to be restored if the soil had dried out and reached the lower humidity level although this is not common, due to the fact that since the last irrigation of the previous crop, a percentage of that water would have been used. That consumption can be estimated by calculating the evapotranspiration that has taken place during that period. During the first few days after the final irrigation, the value of the evaporation from the soil can be considered the same as the reference evapotranspiration (ETo), whose daily value can be obtained from the Red de Información de la Agroclimática de Andalucía (the Andalusian Agroclimatic Information Network). In sanded soils this value is reduced as a consequence of the insulating effect that the sand causes when halting the capillary rise of the water. This will depend on the thickness of the layer of sand and the state in which it is to be found (dirty, clogged, etc.,). For guidance only, in sanded soils we can consider evaporation from the soil to be the same as 50 % of the ETo. An example of the calculation is shown below: We have a greenhouse with sanded soil in the municipality of Vicar (Almeria) in which the previous crop was completed on 2 June 2010. The last irrigation took place on May 31st and the greenhouse was solarised on June 7th. We want to know the water required for solarisation.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Date 1/06/2010 2/06/2010 3/06/2010 4/06/2010 5/06/2010 6/06/2010 7/06/2010

ETo (mm) 6.99 5.21 5.31 5.61 6.22 6.46 4.35

By adding up the week’s totals we arrive at a total of 40.15 mm. As the soil is sanded we estimate a reduction of 50 % and obtain an evapotranspiration figure of:

The estimate for irrigation water will therefore be 20.07 L m-2. To calculate the duration of irrigation we have to know the setting and the flow rate of the emitters. We are supposing that the greenhouse has an irrigation system with two emitters of 3 L h-1 per m-2. In this instance the installation has a flow rate of 6 L h-1. The length of irrigation time would therefore be:

References Baeza Cano, R., Fernández Fernández, M. Solarización de cultivos hortícolas bajo abrigo: Técnicas adecuadas de manejo para una mayor eficacia del método. Boletín trimestral de información al regante. N⁰16. Octubre-Diciembre 2010. Págs 6-7. Instituto de Investigación y Formación Agraria y pesquera. Consejería de Agricultura y Pesca. Bello A, López-Pérez JA, García-Álvarez A, Díaz-Viruliche L. 2003. Biofumigación y control de los patógenos de las plantas. En Biofumigación en agricultura extensiva de regadío (Bello A, López-Pérez JA, GarcíaAlvarez A, eds.). España:Fundación Ruralcaja Alicante: Mundi-Prensa, pp. 343-362. Bretones Castillo, F. (2003). El Enarenado. En Técnicas de producción en cultivos protegidos. Caja Rural Intermediterránea, Cajamar. Castilla, N., Elias, F., Fereres, E., 1990. Caracterizaciónh de condiciones climáticas y de relaciones sueloagua- raíz en el cultivo enarenado del tomate en invernadero en Almeria. Estación Experimental de Cajamar, ‘Las Palmerillas’. Céspedes, A. J., García, M. C., Pérez Parra, J., Cuadrado, I. M. Incidencia de la solarización en la desinfección de los suelos de la horticultura protegida de Almeria. I Congreso Virtual Iberoamericano de Producción integrada en Horticultura 2010. Almeria.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soil cultivation: Characteristics, correction and disinfection Del Castillo, J. A., Uribarri, A., Aguado, G., Astiz, M., Sádaba.Guía de biofumigación y solarización de suelos en invernaderos. Navarra agraria. Enero-Febrero 2012, pp 21-22. García Villar, L. Desinfección de suelos. Horticultura: Revista de industria, distribución y socioeconomía hortícola: frutas, hortalizas, flores, plantas, árboles ornamentales y viveros, ISSN 1132-2950, N⁰ 3, 1982, págs. 15-17. González, J. A., Bello, A., Tello, J. La biofumigación como alternativa a la desinfección de suelos. Horticultura internacional, ISSN 1134-4881, N⁰ 17, 1997, págs. 41-43 López García, C. Desinfección de suelos en invernadero. Horticultura: Revista de industria, distribución y socioeconomía hortícola: frutas, hortalizas, flores, plantas, árboles ornamentales y viveros, ISSN 11322950, N⁰ 139, 1999, págs. 31-34 Sanz de Galdeano, J., Uribarri, A., Sádaba, S., Aguado, G., Del Castillo, J. Biofuminación en invernadero. Navarra agraria. Noviembre-diciembre 2002, pp 25-29. Serrano Cermeño, Z. 1976. Hojas divulgadoras del Ministerio de Agricultura. Los enarenados y su realización. Núm 9/10-76 HD. Zapater Lilla, J. Desinfección de suelos. Horticultura: Revista de industria, distribución y socioeconomía hortícola: frutas, hortalizas, flores, plantas, árboles ornamentales y viveros, ISSN 1132-2950, N⁰ 50, 1989, págs. 142-144

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

The irrigation of greenhouse crops Fernández M.D1; Thompson R.B.2; Bonachela S. 2; Gallardo M. 2; Granados M.R. 2 1 2 Cajamar Research Centre ‘Las Palmerillas’; Universidad of Almeria

Introducción

It is estimated that the water used in agriculture constitutes two-thirds of all the water used in the world, a percentage which tends to be greater in arid and semi-arid regions which have a high agricultural output, like the Mediterranean coast of Spain. In the near future, the greater demand for food, arising out of the anticipated increase in world population and the improving standard of living, will lead to an expanding need for water to irrigate crops and will intensify competition for this increasingly scarce resource. In this context, there is a growing social demand for a use of water which is more productive and sustainable, and for a better understanding of its role in agriculture, the principal user of water. For decades, the province of Almeria has suffered a serious structural shortcoming when it comes to water, originating with a progressive exhaustion of the aquifers of the area (SánchezMartos et al., 1999). Greenhouse agriculture, or “farming under plastic”, with some 27.000 hectares which supply more than 90 % of Almeria’s output of vegetables, is the province’s biggest user. In this context, the Cajamar Research Centre ‘Las Palmerillas’, together with the Universities of Almeria and Cordoba, has since the 1990’s been developing a priority line of investigation whose object is to quantify and to analyze the use of water with greenhouse crops, and to generate tools and methods which will enable us to improve its efficiency and productivity.

Where the water originates

The majority of irrigation water used in the greenhouses of Almeria is of subterranean origin (80 % of these enterprises use underground water - Céspedes et al., 2009), and this has led to overexploitation of the region’s aquifers. In recent years, as in other arid and semi-arid areas of the world, this has given rise to the exploitation of alternative sources of water. Purified recycled water is used, today, as a first source of irrigation water on some 2.000 hectares of greenhouse farmland in the Vega de Almeria and, in the near future, it is expected that a large part of the purified water of the Campo de Dalías will be used. It would be wise to improve the quality of this latter resource, given that the primary, secondary and tertiary treatments carried out are often insufficient or inadequate (Bonachela et al., 2007). Desalinated water, despite its higher cost, is also being progressively introduced in deficient zones or those with water of poor quality in the east of Almeria. Rain water collected from greenhouse covers is, nowadays, a secondary water source in numerous businesses. The extension of this practice throughout the whole surface “under plastic” would help to palliate the irrigation water deficit substantially, given that rainfall on the coast of Almeria could supply almost 50 % of the

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

watering needs of the initial greenhouse crop rotations (Fernández et al., 2007). The collection of condensation water inside the greenhouses could constitute another alternative source, above all in the colder areas. In the greenhouses of the Almanzora valley, we have collected annually up to 40 L m-2 of condensation water, although in warmer areas (El Ejido), the amounts collected were lower. Finally, the re-use of substratum crop run-off, a widespread practice in central European greenhouses, would clearly reduce water needs and would, above all, ease problems of soil-water contamination in the region.

Systems of irrigation and water storage

The greenhouses of Almeria use irrigation systems which allow the distribution of water and fertilizers in a uniform manner (Céspedes et al., 2009). However, the uniformity of this distribution of irrigation water, determined by means of the coefficient of uniformity (Merriam & Keller, 1978), has generally been poor, and has hardly improved in recent decades: Orgaz et al. (1986) found an average coefficient of uniformity of 76 % in the greenhouses of the Campo de Dalías while, recently, Lupiañez (2009) noted an average coefficient of uniformity of 77 % in the same zone. Both values fall below the compulsory minimum (85 %) fixed by the integrated production regulation governing protected horticulture crops in Andalusia (Order of 10 October 2007, BOJA number 211). Taking into account that the majority of greenhouses occupy flat surfaces and irrigation sub-units tend to be small, the uniformity of distribution for irrigation water would have to improve by upgrading the management and maintenance of its watering systems: regulation and control of water pressure in its sub-units: repair of leakages and cleaning of the network, management of reservoirs and filters, etc. (Lupiañez, 2009). Most enterprises which operate greenhouses have irrigation ponds (83.5 %, Cespedes et al., 2009) in order to guarantee water supply for their crops, and these are, generally, small and uncovered (21.7 % are covered). In the province of Almeria, 8.730 ponds larger than 150 m2 have been inventoried, and these occupy some 6.17 km2 and are concentrated in the greenhouse areas (Casas et al., 2011). If the reservoirs were to be covered with plastic mesh, the estimated saving would be in the order of 6.9 hm3, assuming an annual average evaporation rate of 1.404 L m-2. However, the saving in water derived from covering the ponds would be lower than the cost of covering them in most of the greenhouse areas (Martínez Álvarez et al., 2009). On the other hand, in areas with scant natural aquatic ecosystems, such as the coast of Almeria, the open irrigation ponds play an important environmental role in the conservation of biodiversity (Casas et al., 2011).

Irrigation water supply

The average supply of irrigation water for the main horticultural crops in soil (tomatoes not included), measured over six consecutive farming seasons (1993/94 - 1998/99) across 41 representative greenhouses of the Campo de Dalías (Fernández et al., 2007), was 228 L m-2 per cultivation cycle and varied between 158 L m-2 for green beans in autumn-winter and 363 L m-2 for peppers in autumn-winter. In a similar study in the Campo de Níjar, the average supply for an autumn-spring tomato was 558 L m-2 (Carreño et al., 2000). These values are clearly lower

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

than the supply for open air crops (Fernández et al., 2007), owing, above all, to the lower requirement due to evaporation inside the greenhouse (less solar radiation, less wind), in comparison with the open (Orgaz et al., 2005), and also because greenhouse crops tend to grow in winter-based cycles, while open-air crop cycles are usually summer-based (Orgaz et al., 2005).. Supply per season is generally higher than per crop cycle, because annual two-crop rotations are frequent. The average supply for the principal greenhouse crops for the Campo de Dalías varied between 363 (autumn-spring peppers) and 502 L m-2 (autumn-winter peppers and spring melons), with an average value of 444 L m-2 (Fernández et al., 2007). Total annual supply tends to be greater still, since it is common to undertake disinfection waterings, the washingoff of salts and maintenance work on the irrigation system between growing seasons. When these supplementary waterings are taken into account (Peña, 2009), the total estimated average value for the annual supply in the Campo de Dalías is 495 L m-2.

4.1 Indicators of irrigation water use The analysis of irrigation water use in agriculture is undertaken by means of a series of internationally-established indicators (Malano & Burton, 2000), and the most representative for the scale of use-per-plot are:   

Relative supply of irrigation water: the quotient between the irrigation water supplied (L m-2) and that needed to cover cultivation needs (L m-2); Productivity of irrigation water (€ m-3): the quotient between the economic value generated by the crop (€ m-2) and the irrigation water supplied (m3 m-2); Efficiency in the use of irrigation water (kg m-3): the quotient between the commercial performance of the c rop (kg m-2) and the irrigation water supplied (m3 m-2).

The average value of the relative input of irrigation water to the main crops of the Campo de Dalías was 1.13 (Fernández et al., 2007), which suggests that the growers used, on average, 13 % more water than was needed by the crops. This is an acceptable average value, given that the growers are looking to maximize the performance and the quality of their goods. However, there was a high variability in each cycle of the cultivation (raised coefficients of variation) and between cycles (Table 1). Thus, the average relative input for cucumbers was 1.63, which is to say, this crop, on average, was watered extremely excessively. What is more, the relative inputs of irrigation water were very excessive during the establishment phase of all crops and, to a lesser extent, during their development (Fernández et al., 2007). This indicator shows that we can improve our use of water in the greenhouses by adjusting input to irrigation needs. The productivity of irrigation water fluctuated between 7.8 and 15.9 € m-3 (Table 1), values much higher than those of other Andalusia and Spanish irrigation zones (Lorite et al., 2004), owing to lower water inputs and, above all, to the higher productivity and economic value of the greenhouse orchard produce.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops The average efficiency in the use of irrigation water varied between 15.3 and 35.6 kg m3 (Table 1), values lower than those measured in substratum crops in central European greenhouses. On the other hand, these values are, in general, higher than for the same crops cultivated in the open air, owing to the lower input of water and to the greater productivity of the greenhouse (Fernández et al., 2007). RIS

Supply (L m-2)

IWUE (kg m-3)

WP (€ m-3)

Cycle

Pepper Aut/Win

311 (32)

0.95 (36)

2.78

1.27

0.91

21.0(40)

13.1(50)

Cucumber

270 (40)

1.62 (40)

3.53

1.48

1.20

33.2(52)

12.4(59)

Bean Aut/Win

158 (33)

1.18 (24)

4.28

1.06

0.76

15.3(45)

15.9(45)

Melon

177 (31)

1.00 (39)

3.52

1.19

0.52

22.8(34)

10.1(44)

Watermelon

189 (38)

0.92 (33)

2.41

1.27

0.42

35.6(34)

7.8 (46)

Bean (Spring)

197 (24)

1.03 (28)

4.25

1.80

0.60

16.8(31)

15.4(53)

Pepper Aut/Sp

363 (30)

1.02 (27)

4.85

0.88

0.68

16.9(23)

8.7 (40)

Cycles

Table 1: average values (coefficient of variation in brackets) of inputs and relative inputs of irrigation water (RIS), efficiency in its use (IWUE) and productivity of irrigation water (WP) in the major orchard produce cultivation cycles in the greenhouses of the Campo de Dalías. RIS values are presented for the entire cultivation cycle and for three periods during the course of the same: crop establishment (1): crop cultivation (2): and from halfway to the end of the cycle (3)

Programming in-greenhouse irrigation

Programming irrigation is a set of technical procedures developed by asking in advance when and how much to apply in order to cover the needs of the crops, and its importance is highlighted when water is a scarce resource and its cost is high. Irrigation programming can be carried out based on measurements of soil water content, measurements of the plant’s water status or from climate data.

5.1 Programming irrigation by means of sensors Sensors which measure soil and plant water content can be used as the basis of water management, or as auxiliaries for other methods. These sensors allow us to adapt thse management of irrigation to the individual characteristics of each crop, or each farm. Until the late 1980’s, most of these sensors required manual handling and their use on commercial farms was very limited. Recent technological development, however, has enabled the introduction of a new generation of sensors, equipped with new features. Today, data on the water content of the soil or the plant can be sent directly to a laptop computer, mobile phone or irrigation control mechanism. In the greenhouse, owing to the high frequency of watering

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

and the low evaporation requirements the growing environment remains continually humid. The small surface area of these farms and the intensive management of the greenhouses favour the use of monitoring via technology. 5.1.1 Programming Irrigation with soil moisture sensors The moisture sensors in the soil measure (i) the volumetric moisture of the soil (Θv), or (ii) the potential of the soil matrix (m). The Θv is the proportion of the soil volume taken up by water. The m indicates the availability of water for the crops (Gallardo & Thompson, 2003a). The Θv is a measurement which requires interpretation (Thompson & Gallardo, 2003). The soil sensors can be read manually or automatically, which enables a more detailed gathering of information on the dynamics of water use crops, and its movement through the soil. The soil sensors can be used with different configurations (Thompson & Gallardo, 2003); one sensor must always be in the zone of maximum root concentration. More sensors can be placed at different depths, for example beneath the roots, to control run-off. Irrigation management using sensors is based on maintaining the moisture between two limits, a lower one which indicates the driest values of the soil when watering must begin and an upper one, which indicates the moistest values allowed. The difference between the two limits is an indication of the volume of watering required (Figure 1). Sensors which measure the soil matric potential In saline conditions, the m is a good approximation of the total soil water potential (s); the m measures the strength with which the water is retained by the soil particles, and indicates the soil water availability to the plant. In saline conditions (whether in soil or water), the osmotic potential can contribute significantly to the s. This contribution of salinity to the potential is managed independently in the field. Some authors and equipment manufacturers have indicated the upper and lower limits between which the m can be found in the root zone, for horticultural production in soil: differences are established between texture, crop species and evaporation conditions. In the case of frequently irrigated greenhouse horticultural products, general recommendations for the m intervals are between -10 & -20 kPa, -10 & -30 kPa, and -20 & -40 kPa for soils of thick, medium and fine texture respectively.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

Figure 1: Example of soil moisture maintenance, between limits. (CUANTO regar = HOW MUCH to water, CUANDO regar = WHEN to water, LIMITE SUPERIOR = UPPER LIMIT, LIMITE INFERIOR = LOWER LIMIT)

There are two groups of matrix potential sensors which are relevant for protected horticultural crops: tensiometers, and granular matrix sensors. Tensiometers are cheap, simple and easy to use. They require adequate preparation and maintenance if they are to provide accurate and reliable data (Thompson & Gallardo, 2003). There are (i) manual tensiometers, from which data is obtained by taking a visual vacuometer reading, (ii) manual tensiometers with a switch for activating the irrigation equipment when a predetermined point is reached, and (iii) electric tensiometers which contain pressure transducers: these allow continuous automatic data measurement, and can act as irrigation monitors. Tensiometers usually have a working range of 0 to -80 kPa. This reduced range is a limitation with certain systems of cultivation, but generally with protected horticultural crops, the m remains within these limits. There are certain exceptions, when the evaporation demand and the leaf surface are high, for example in the cultivation of melons, during May - June in the south-east of Spain. Granular matrix sensors are electrical resistance sensors and consist of a matrix with two electrodes. The most common is the Watermark (Irrometer Co. California, USA). The water inside the matrix reaches a balance with that in the soil. The measurement of the electrical resistance between the two electrodes is a function of the soil matric potential. These sensors are cheap, simple and easy to install, with very few requirements when it comes to preparation and maintenance. Their measuring range is between -10 and -200 kPa. The range is broader than that of the tensiometers, but they are not very reliable in extremely moist soils (0 a -10 kPa), and they are slow to respond in rapidly-drying soil (Thompson et al., 2006). In general, they are less accurate than tensiometers, but need less maintenance by the user. Readings are taken manually with a reading device, or automatically, and the sensor has a working life of 5-7 years.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

Figure 2: (left to right): A manual tensiometer, a manual tensiometer placed in sandy soil, a “Watermark” sensor and a “Watermark” reading device.

Sensors which measure the volumetric contents of soil water Of the group of sensors which measure volumetric moisture in the soil (Θv), the most suitable for orchard produce cultivation systems “under plastic” are the di-electric sensors (Thompson & Gallardo, 2003). There are two types: (i) TDR (Time Domain Refractometry) and (ii) the capacitance sensor, or FDR (Frequency Domain Refractometry). TDR sensors, composed of stainless steel bars of >10 cm, are used quite often in investigation. Capacitance sensors, in addition to their use in investigation, are also employed in the management of irrigation in commercial settings. These latter are marketed in various configurations, e.g. as bars or rings of various thicknesses (Thompson & Gallardo, 2003; Fig. 3).

Figure 3. Capacitance sensors: Various “EnviroSCAN” sensors, (1) employed in taking samples, (2) positioned in the soil, (3) an ECHO sensor, and (4) the WET sensor, with its reader

The capacitance sensor most often used for the management of irrigation is the EnviroSCAN (Sentek Technologies, Australia), which consists of various ring-type sensors, mounted vertically on a probe, at various depths (Fig. 3). This equipment records continuous moisture data, sending detailed information about the dynamic state of the ground water, both in the root zone and below. The EnviroSCAN is relatively expensive and sensitive to changes in soil salinity (Thompson et al., 2007), which limits its use to systems where salinity must be controlled to improve the quality of the fruit. Some di-electric sensors and tensiometers have been used in the management of irrigation of substrate grown crops (Thompson & Gallardo, 2003). These di-electric sensors include the

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

EnviroSCAN (Fig. 3), WET sensor (Delta-T Devices, United Kingdom; ¡Error! No se encuentra el origen de la referencia.), ECHO sensor (Decagon Devices, USA), and the Grodan WCM Continuous Sensor (Grodan, Holland). The reduced-scale tensiometers (e.g., 0 to -40 kPa) and rapid-response have been used with artificial substrata and with cultivation bases such as sand. 5.1.2 Programming irrigation with plant sensors The plant sensors which have the greatest number of applications for irrigation management are: (i) sensors of stem diameter, (ii) sap flow sensors, and (iii) leave or cover temperature sensors (Gallardo & Thompson, 2003b). Sensors of stem diameter measure the contraction of the stem which occurs during daylight hours, in response to transpiration, and also measure the growth of the stem: both of these parameters are extremely sensitive to “water stress”. In recent years, there has been a great deal of research into woody crops using these sensors and a certain degree of adoption by commercial farms. With greenhouse crops, these sensors can be indicators of “water stress”: however, in short-cycle crops, the rapid growth rate makes it much more difficult to interpret the data: what is more, when used with greenhouse crops, their ability to detect “water stress” diminishes in greenhouse conditions, with low evaporation demand (Gallardo et al., 2006). In a similar manner, sap-flow sensors which measure the plant’s transpiration directly have been the subject of research, above all with woody plants. These sensors, owing to their high cost and technical complexity, have been used mostly in research and there are few horticultural applications for them in the management of irrigation. The difference in temperature between the leaf and the rest of the plant and the ambient environment is also a sensitive indicator of water stress. Various indicators have been put forward for irrigation control based on this measurement, such as the CWSI (“Crop Water Stress Index”), but although up to now there have been no commercial applications, work is currently under way on this method, in combination with tele-detection. In general, plant sensors have found fewer practical applications in the management of irrigation than soil sensors. 5.1.3 General considerations: sensors in irrigation management When we use sensors in irrigation management, we must consider (i) replication with a minimum of 2 or 3 sensors for a given crop, and (ii) the positioning of those sensors, which must be representative of the whole crop. Other considerations are the cost, ease of use, preparation, maintenance, technical support, ease of data interpretation, availability of irrigation protocols, the language in which the work will be undertaken and the availability of user-friendly software for equipment which requires the use of a computer (Thompson & Gallardo, 2003). In general soil sensors are easier to use for irrigation management than plant sensors, and the progress in irrigation protocols has been significant. Soil capacitance sensors are used currently on commercial farms in other countries. However, two important limitations are their cost, and their heightened sensitivity to salt. Tensiometers are very adequate sensors for greenhouse crops in soil because they are simple, cheap and reliable. They are not affected by soil salinity and their working range is not normally a limitation for this type of crop, in soils which are generally moist.

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

5.2 Programming irrigation, using climatic data Programming irrigation using climatic data is based on the use of mathematical expressions which, starting from climatic data, enable us to estimate the volume of water consumed by crops, or the crops’ evapotranspiration (ETc). When sprinkler systems are used, given the higher irrigation frequency, there is a tendency to disregard the role of the soil as a water store and to assume that the water content in the soil does not vary over time. Thus, for protected crops, programming the irrigation is simpler and the programming process concentrates on how much water must be applied, based on the ETc estimates. Climatic data must come from agro-meteorological stations, based in farming areas where their instruments will be exposed to atmospheric conditions similar to those met by the surrounding crops (Allen et al., 1998). Further, it should be borne in mind that the estimates for crop water consumption will not exceed those of the climatic data used. Therefore, before making estimates of crop water consumption, it is highly recommended that the quality of the climatic data be evaluated, in order to detect any errors. Various procedures have been developed for evaluating such data in a straightforward way (Meek & Hatfield 1994; Allen et al., 1998). 5.2.1 Models for estimating the crop water requirements In greenhouses with climate control systems, and with substrate crops, models have been developed which permit the estimation of crop transpiration on an hourly scale, or even more precisely (Stanghellini, 1987; Baille et al., 1994; Medrano et al., 2005). The use of these models in greenhouses with low technology levels can be complicated, because it is necessary to use: (i) hourly climatic data in real time, (ii) data which refer to the crop, such as aerodynamic resistance, and the index of leaf area, about which there is scant information, or which are difficult to measure, and (iii) we have to know how the model parameters vary with climatic conditions, the species of the crop and its stage of development. In greenhouses which lack climate control and have a low level of technology, and if, what is more, they use soil as the growing medium; it might be more advisable to use simpler systems. Empirical relationships between crop transpiration and solar radiation have been proposed (de Villele, 1974), or the nexus between evapotranspiration and a Class A Tank (Castilla, 1986). However, these relationships vary with climatic conditions, the species under cultivation and the stage of the plant’s development, since the coefficients of these relationships include both the effects of climate and the effects of the crop itself on water demand. The FAO model (Doorenbos & Pruitt, 1977) permits us to separate the effects of climate and those of crops on water consumption, enabling the model’s application in a variety of climatic conditions, and with different crops. This model estimates the crop’s consumption of water, or evapotranspiration (ETc), as the product of evapotranspiration of a notional grass crop (ETo), which quantifies the effect that the climate has over the crop’s water demand, and the coefficient of the crop (Kc), which varies with the crop in question, its state of development

100

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

and the availability of soil water: it serves as an integration of the physical and physiological differences between the crop and its notional counterpart.

This model, widely used with open-air crops, has been calibrated and evaluated in the Cajamar Research Centre ‘Las Palmerillas’ for use with horticultural crops under plastic in the south east of Spain (Fernández et al., 2001; Orgaz et al., 2005; Bonachela et al., 2006; Fernández et al., 2010). There are numerous expressions which enables us to estimate the ETo from climatic data, but the FAO-56 Penman-Monteith method (Allen et al., 1998) has been recommended as the standard calculative procedure for its precision both in arid and humid climates. It requires data on radiation, air temperature, atmospheric humidity and wind velocity. Under plastic in the Mediterranean climate, this method has provided great accuracy when used with a fixed value for aerodynamic resistance of 295 s m-1 (Fernández et al., 2010). Furthermore, the methods of Hargreaves and a method using local radiation also gave precise estimations, and given the scant climatic data which they require, and their simplicity - they are recommended for use in these conditions (Fernández et al., 2010). The local radiation method allows the estimation of ETo values under plastic from solar radiation values measured outside, and of the transmissivity of the greenhouse plastic, which is a function of the type of structure, the covering material, the age of the plastic, etc. The main advantage of this method is the possibility of adapting the irrigation dosage to different types of sunlight-management (whitewashing, various types of shading), various greenhouse structures and covering materials, starting from the transmissivity of the cover. The Kc values for the main greenhouse crops have been determined for conditions in the southeast of Spain (Fernández et al., 2001; Orgaz et al., 2005). A model has also been developed which estimates Kc values as a function of temperature, measured inside the greenhouse (Fernández et al., 2001; Orgaz et al., 2005), which offers a simple means of adapting the irrigation dosage to different climatic conditions or planting dates. A software programme has been developed, using the FAO model, adapted for the greenhouse - PrHo v 2.0 (© 2008 Fundación Cajamar; Fernández et al., 2008) and recommendations for irrigation have been evolved, based on average climatic data for outdoor solar radiation and the internal temperature of the greenhouse, over a historical series of more than twenty years (Fig. 4). The objective is to provide technicians and farmers with easily-usable tools which will enable them to optimize the use of water on horticultural crops grown under plastic.

101

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

Figure 4: “PrHo: Irrigation Programme for Horticultural Crops”, a publication produced by the Cajamar Research Centre ‘Las Palmerillas’, containing recommendations for the irrigation of horticultural crops.

References ALLEN, R.G.; PEREIRA, L.S.; RAES, D.; SMITH, M. (1998): "Crop evapotranspiration. Guidelines for computing crop water requirements”. FAO Irrigation and Drainage Paper 56, Roma, FAO. BAILLE, M.; BAILLE, A.; LAURY, J.C. (1994): "A simplified model for predicting evapotranspiration rate of nine ornamental species vs. climate factors and leaf area"; en Scientia Horticulturae (59); pp. 217-232. BONACHELA, S.; GONZÁLEZ, A.M.; FERNÁNDEZ, M.D. (2006): "Irrigation scheduling of plastic greenhouse vegetable crops based on historical weather data"; en Irrig. Sci. (25); pp. 53-62. BONACHELA, S.; ACUÑA, A.R.; CASAS, J. (2007): “Environmental factors and management practices controlling oxygen dynamics in agricultural irrigation ponds in a semiarid Mediterranean region: Implications for pond agricultural functions”; en Water Res. (41); pp. 1225-1234. CARREÑO, J.; AGUILAR, J; MORENO, S.M. (2000): “Gastos de agua y cosechas obtenidas en los cultivos protegidos del campo de Níjar (Almeria)”. XVIII Congreso Nacional de Riegos. Huelva, 20 al 22 de junio de 2000. CASAS, J.J.; TOJA, J.; BONACHELA, S.; FUENTES, F.; GALLEGO, I.; JUAN, M.; LEÓN, D.; PEÑALVER, P.; PÉREZ, C.; SÁNCHEZ, P. (2011): “Artificial ponds in a Mediterranean region (Andalusia, southern Spain): agricultural and environmental issues”; en Water and Environ. J. (25-3); pp. 308-317.

102

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

CASTILLA, N. (1986): “Contribución al estudio de los cultivos enarenados en Almeria: Necesidades hídricas y extracción de nutrientes del cultivo de tomate de crecimiento indeterminado en abrigo de polietileno”. Universidad Politécnica de Madrid. CÉSPEDES, A.J.; GARCÍA, M.C.; PÉREZ-PARRA, J.J.; CUADRADO, I.M. (2009): “Caracterización de la explotación protegida almeriense”. Almeria, FIAPA, Fundación Cajamar. DE VILLELE, O. (1974): "Besoins en eau des cultures sous serre. Essai de conduite des arrosages en fonction de l'ensoleillement"; en Acta Hortic. (35); pp. 123-129. DOORENBOS, J.; PRUITT, W.O. (1977): "Las necesidades de agua de los cultivos”. FAO Riego y drenaje n⁰ 24, Roma, FAO. FERNÁNDEZ, M.D.; ORGAZ, F.; FERERES, E.; LÓPEZ, J.C.; CÉSPEDES, A.; PÉREZ, J.; BONACHELA, S.; GALLARDO, M. (2001): "Programación del riego de cultivos hortícolas bajo invernadero en el sudeste español". Almeria, Cajamar (Caja Rural Intermediterránea). FERNÁNDEZ, M.D.; GONZÁLEZ, A.M.; CARREÑO, J.; PÉREZ, C.; BONACHELA, S. (2007): “Analysis of onfarm irrigation performance in Mediterranean greenhouses”; en Agric. Water Manage. (89); pp. 251260. FERNÁNDEZ, M.D.; CÉSPEDES, A.; GONZÁLEZ, A.M. (2008): “PrHo V. 2.0: Programa de Riego para cultivos Hortícolas en invernadero”. Documento Técnico (1). Almeria, Fundación Cajamar. FERNÁNDEZ, M.D.; BONACHELA, S.; ORGAZ, F.; THOMPSON, R.B.; LÓPEZ, J.C.; GRANADOS, M.R.; GALLARDO, M.; FERERES, E. (2010): " Measurement and estimation of plastic greenhouse reference evapotranspiration in a Mediterranean climate"; en Irrig. Sci. (28); pp. 497-509.

GALLARDO, M; THOMPSON, R.B. (2003a): “Relaciones hídricas en suelo y planta”; en FERNÁNDEZ, M. et al., (eds): Mejora de la Eficiencia en el Uso del Agua en Cultivos Protegidos. Dirección General de Investigación y Formación Agraria de la Junta de Andalucía; pp. 71-94. GALLARDO, M.; THOMPSON, R.B. (2003b): “Uso de los sensores de planta para la programación del riego”, en FERNÁNDEZ, M. et al., (eds): Mejora de la Eficiencia en el Uso del Agua en Cultivos Protegidos. Dirección General de Investigación y Formación Agraria de la Junta de Andalucía; pp. 353-374. GALLARDO, M; THOMPSON, R.B.; VALDEZ, L.C.; FERNÁNDEZ, M.D. (2006): “Response of stem diameter variations to water stress in greenhouse-grown vegetable crops”; en Journal of Horticultural Science&Biotechnology (81); pp. 483-495. LORITE, I.J.; MATEOS, L.; FERERES, E. (2004): “Evaluating irrigation performance in a Mediterranean environment. II. Variability among crops and farmers”; en Irrig. Sci. (23); pp. 85-92. LUPIAÑEZ, N. (2009): “Caracterización y evaluación de instalaciones de riego localizado del Campo de Dalias”. Proyecto Fin de Carrera, Universidad de Almeria. MARTÍNEZ ÁLVAREZ, V.; CALATRAVA LEYVA, J.; MAESTRE VALERO, J.F.; MARTÍN GÓRRIZ, B. (2009): “Economic assessment of shade-cloth covers for agricultural irrigation reservoirs in a semi-arid climate”; en Agric. Water Manage. (96); pp. 1351-1359. MERRIAM, J.L.; KELLER, J. (1978): “Farm Irrigation System Evaluation”. Utah, State University.

103

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The irrigation of greenhouse crops

MALANO, H.; BURTON, M. (2000): “Guidelines for Benchmarking Performance in the Irrigation and Drainage Sector”. IPTRID Secretariat, FAO, Rome. MEDRANO, E.; LORENZO, P.; SÁNCHEZ-GUERRERO, M.C.; MONTERO, J.I. (2005): "Evaluation and modelling of greenhouse cucumber-crop transpiration under high and low radiation conditions"; en Scientia Hortic. (105); pp. 163-175. MEEK, D.W.; HATFIELD, J.L. (1994): "Data quality checking for single station meteorological databases"; en Agricultural and Forest Meteorology (69); pp. 85-109. ORGAZ, F.; BONACHELA, S.; CUEVAS, R.; DE LOS RIOS, E.; MONTERO, J.I.; CASTILLA, N.; FERERES, E. (1986): “Evaluación de sistemas de riego localizado en cultivos bajo invernadero en Almeria”. II Congreso Nacional de la S.E.C.H. 21-25/04/1986, Córdoba, España. ORGAZ, F.; FERNÁNDEZ, M.D.; BONACHELA, S.; GALLARDO, M.; FERERES, E. (2005): "Evapotranspiration of horticultural crops in an unheated plastic greenhouse"; en Agric. Water Manage. (72); pp. 81-96. PEÑA, M.T. (2009): “Estimación a escala regional de los flujos de agua y la lixiviación de nitratos en el Campo de Dalías”. Proyecto Fin de Carrera, Universidad de Almeria. SÁNCHEZ-MARTOS, F.; PULIDO-BOSCH, A.; CALAFORRA, J.M. (1999): “Hydrogeochemical processes in an arid region of Europe (Almeria, SE Spain)”; en Applied Geochemistry (14); pp. 735-745. STANGHELLINI, C. (1987): “Transpiration of greenhouse crops: an aid to climate management”. Ph.D. Dissertation. Wageningen Agricultural University, The Netherlands. THOMPSON, R.B.; GALLARDO, M. (2003): “Programación de riegos mediante sensores de humedad en suelo”, en FERNÁNDEZ, M. et al., (eds): Mejora de la Eficiencia en el Uso del Agua en Cultivos Protegidos. Dirección General de Investigación y Formación Agraria de la Junta de Andalucía; pp. 375-402. THOMPSON, R.B.; GALLARDO, M.; AGÜERA, T.; VALDEZ, L.C.; FERNÁNDEZ, M.D. (2006): “Evaluation of the Watermark sensor for use with drip irrigated vegetable crops”; en Irrigation Science (24); pp. 185202. THOMPSON, R.B.; GALLARDO, M.; FERNÁNDEZ, M.D.; VALDEZ, L.C., MARTÍNEZ-GAITAN, C. (2007): “Salinity effects on soil moisture measurement made with a capacitance sensor”; en Soil Science Society of America Journal (71); pp. 1647-1657.

104

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

Fertirrigation Juan José Magán Cañadas (1); Mª Dolores Fernández Fernández (1); Thompson R.B.(2); Granados M.R.(2) 1 2 Cajamar Research Centre ‘Las Palmerillas’; Universidad of Almeria

The Concept of fertirrigation

Fertigation consists of the joint application of water and fertilizers. It tends to be associated with a fixed irrigation system, such as a sprinkler set-up, since this enables the maximum use and permits the farmer to obtain some important advantages. In concrete terms, the use of fertigation in combination with a fixed irrigation system allows the introduction and concentration in the plant roots of the fertilizers which these need for their development and bringing about, by means of correct management, efficient use and minimization of the losses which occur through leaching where non-fixed systems are used. In the same way, it allows savings in water and fertilizers, and apportions these resources in keeping with the cultivation needs of the given moment. The technique of fertigation can be applied both to soil cultivation and to the soillessmethod, though there are certain differences between the two systems, such as they are, at the moment of undertaking their handling.  A reservoir of nutrients exists in the soil, while soilless scultivation makes use of inert substrates or, at any rate, soil of scant volume. Accordingly, with soil-based fertigation there is the possibility of non-application, or applying at a distance, of certain nutrients (as, for example, phosphorus or micro-elements), or of irrigation without fertilizers. What is more, it is often the case that water alone is applied at the beginning (pre-irrigation) or at the end (post-irrigation) of the irrigation. Against this, soilless cultivation is provided with a complete solution throughout the entire irrigation process  The change complex which exists in the soil brings about the absorption of cations, and this makes it possible to increase the supply of ammonium, without causing toxicity. With soilless cultivation it is possible to maintain more optimal root conditions than in soil, and management should aim to achieve the ideal pH, so that the supply of ammonium should be adjusted in accordance with the pH of the substrate solution  When cultivating in soil, the management of fertigation often revolves around vigour, and the obtainment of quality fruit, such that the cultivation tends to be more vegetative than that carried out in substrates, where the tendency is to achieve a cultivation balanced between vegetation and fruit-production

105

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

In order to achieve highly-effective fertigation when cultivating in soil, it is necessary to start with a soil in the most optimal conditions possible in terms of the presence of organic matter, level of exchangeable sodium, etc. It is essential to carry out a reliable analysis of the soil at the start of the season, before planting. By means of this analysis, we will know if it will be appropriate to supply a certain amount of fertilizer to augment the levels of organic matter, apply gypsum to release excess sodium absorbed in the change complex, add sulphur to adjust soil alkalinity, etc. This allows us to know the levels of fertility, principally in so far as phosphorus and potassium are concerned, and to know if it is necessary to add them as basal dressing for the purpose of starting the fertigation from desirable levels. These levels are appropriate as a safety reserve against possible deficiencies which can arise in the fertigation. In this basal dressing, traditional fertilizers can be used such as ammonium sulphate, superphosphate of lime and potassium sulphate, which must be added well before planting in order to avoid damaging crop roots. A couple of good irrigations before transplantation will have the desired effect. Slow-release fertilizers can also be used in order to avoid this problem but, since they release during cultivation, control may be lost. In this chapter, we will deal solely with management of fertigation in soil, and crops in soilless conditions will be discussed in another chapter.

Criteria for fertirrigation in soil

Once the soil conditions are adequate, the moment has arrived to start fertigation with the aim of supplying the crop’s nutritional requirements. For this, two criteria can be adhered to: one, more traditional, consists in adapting the supply of nutrients in the quantitative sense, to the crop’s theoretical needs at each moment: the other is more physiological and of a more qualitative nature, which seeks to provide an ionically balanced physiological solution so that it contains all the nutrients the crop requires. This latter is the criterion used in hydroponics and the one which is being extrapolated for the actual crop in its soil. Let us look at each of these.

3 Criterion of fertilizer application, according to the crop’s theoretical needs This consists in applying at each stage of the crop’s cultivation cycle the quantity of essential elements which the crop is expected to absorb, and which are necessary for its development. For this, it is firstly necessary to estimate the final harvest expected and, proportionally, the necessary quantities of each nutrient must be calculated. These will be a given amount according to the weight of the final yield, and there will be variations according to the species we are dealing with. The next step is to divide the total quantities of each nutrient needed amongst the separate stages of the crop’s development cycle, allowing for the requirements of each one of these, and in turn share these out evenly among the different irrigations which will be carried out in each phase. Finally, the only thing which remains to be done is to convert the required amount of each nutritional element into quantities of commercial fertilizers to be applied.

106

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

The problem is that it is not always possible to undertake local studies of nutrient absorption rates and what is more, where they have been done they were carried out in environmental conditions and times of year which may not match the circumstances of our specific case. Given the scarcity of information concerning the absorption of nutrients by the crops, traditionally, when the time came to make recommendations, what are known as “absorption ratios” were used. These are the quantities of nutrients absorbed, relative to the amount of nitrogen required by the crop. Thus, for example, if we suppose that a crop at a given point in its development has the following absorption ratio: 1:0.3:2.5, this is another way of saying that for every unit of fertilizer N which is absorbed, 0.3 of P2O5 and 2.5 of K2O will also be required. Therefore, the fertilizers which are applied must be kept to the mentioned ratio. When the ratio between the nutrients is being established, the condition of the crop will have to be borne in mind, as will the function of each nutrient. These are:  Nitrogen: Part of the proteins and has an enormous effect on plant growth, adding volume to the vegetative organs. Used in excess, it can cause over-exuberant growth, rendering the crop vulnerable to attack by diseases, and for this reason it is usual to limit its application in the early stages, to avoid this excess of vigour  Phosphorus: Its main role is as an energy transporter (ATP) and it influences the growth and development of the root system. In the same way, it acts on the development of the flower. Normally, it is applied more intensively at the outset of cultivation  Potassium: This is the element which has the greatest influence on fruit quality, given that it acts on the consistency and content of the fruit sugars. In winter it has an important parallel impact on the functioning of photosynthesis and, because of its isotopic properties, emits  and  radiation, the energy from which adds to that of daylight, activating photosynthesis. In the case of excessive use, the plant reaches levels of consumption which are extravagant. This has special importance during the fruiting period  Calcium: Apart from its metabolic functions, calcium is the plastic element par excellence, forming the main part of cell walls. The plant absorbs it passively, and for this reason it is difficult for it to move up to the fruits in conditions of high salinity in the roots, and/or circumstances of intense transpiration. Calcium deficiency can lead to serious physical ailments (blossom-end rot in tomatoes and peppers, for instance)  Magnesium: It is the essential component of chlorophyll and is therefore fundamental for the process of photosynthesis  Sulphur: It is a vital component of certain amino acids and proteins However, with the absorption ratios, we do not know the precise quantities of nutrients to apply. A total quantity of fertilizer whose magnitude varies between 1 and 6 kg for every 1.000 m2 of crops is generally recommended, and the hour of irrigation depends on the crops’ stage of development. Logically, we start with the lowest dosage at the beginning of the crop and we increase it as the need arises. Normally, one aims for a maximum quantity of fertilizer in

107

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

irrigation water of approximately 1 gram per litre, with the aim of avoiding excessive electrical conductivity, which harms the crop, though situations may arise in which it is desirable to increase the dosage.

4 Criterion for fertilizer application, based on an ionically balanced physiological solution Although the criterion for the application of fertilizers described in the previous section is valid and, in actual fact, has been in use for many years, in reality it has fallen into disuse with the widespread introduction of automatic sprinkler heads which regulate the injection of fertilizers, monitoring electrical conductivity and pH. With these systems, a percentage is displayed for each injection, for each of the stock solutions prepared, establishing a nutritional mix which remains constant throughout irrigation. This change of criteria is supported by the idea that the aim of fertilization must be the achievement of a nutritive solution in the plant’s rhizosphere which is the optimum for it, and which must be ionically balanced. This substance should undergo as little variation as possible, so that the crop will not be affected. Thus, it seems logical to try to obtain that balance, basing the effort on other inputs which will be provided. This criterion is the one which has been used classically and which continues to be used with soilless crops, but is now being employed on crops in soil. The problem is that the ionic balance of the former is often used on the latter, and this should not happen, because the soil is not an inert substratum, as is the case with rock wool or perlite, and it interacts with the solution, absorbing some ions and releasing others, until it reaches a dynamic balance. Also, it can happen that, if the same nutritive solution is applied to soil which has received other previous treatments, the solution in the rhizosphere will be different in each zone. This is to make clear that the application of fertilizers needs to be different on each of the different plots, even though we are dealing with the same crop. In reality, it is not easy to know what the ideal nutritive solution to apply in a set of given circumstances is, because of the reaction of the soil to the solution. The best thing to do is to monitor the evolution of the rhizosphere solution, and adapt the applied solution in order to bring the former into as close an approximation as possible with the desired mix for the crop in question. The classic method which has been used for ascertaining the availability of nutrients in the soil solution is the “saturated extract”. However, at present, the use of suction probes, due to the advantages they offer, appears to be becoming more popular. A suction probe is a porous element (usually a porous ceramic) which can vary in shape and size, by means of which the consistency of the soil can be penetrated, and a vacuum applied to the apparatus. The porous element is attached to a PVC or metal tube of a slightly larger diameter, and of variable length, depending on the depth needing to be sampled. The PVC tube is, in turn, sealed with a rubber plug, through which a small-diameter tube with semi-rigid

108

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

walls is inserted and connected to the vacuum device. Once the sample has been collected in the suction probe’s chamber, it can be extracted via the discharge tube by applying compressed air through the vacuum tube. The use of suction probes on greenhouse horticultural crops promises to be very viable, given that it is the only way to extract samples of the soil mix in situ, without diluting the mix itself. In this way, we can find the ionic composition of the ground solution through chemical analysis, and not just by means of its electrical conductivity, as happens with the other in-situ techniques. Like this, the extraction of the sample is easy and low-cost, and does not alter the soil (the reverse of what happens with the conventional sampling techniques for soil analysis. Similarly, once the liquid sample has been obtained, analysis is rapid and inexpensive. According to the results obtained by Lao (1998), the suction probe acts not only as an excellent pH sampler, but for electrical conductivity, nitrates, potassium, phosphates and sodium as well. For calcium, magnesium, ammonium and chlorides there is a downward revision of 15 %, which can be assumed from a nutritional point of view. On the other hand, bicarbonates and sulphates present important alteration values and, because of this, their determination in the soil solution by means of suction probes need not interest us. The rules for the use of suction probes recommended by Lao (1998) are reflected in the table below. STEPS PRELIMINARY TO INSTALLATION

 WASHING (HCl o HNO3 1 N) 24 hours, then later with water. Load the probes in a bucket of water.  VERIFICATION OF SUCTION CAPACITY. Test whether the volume obtained is greater than 100 cc, and if the level of vacuum is maintained when the valve is opened after 24 hours.

INSTALLATION

 Nº of probes: minimum 2 probes per plot (detect extreme values for same)  Position in the greenhouse: After sampling and obtaining CE, choose the points with extreme values. Do not sample on the perimeters.  Position relative to the plant: In the drop-catching line, 10 cm away from the plant.  Depth: Sanded soil: 10 cm Soil: As close to the root system as possible.

1.-Siting

2.- Installation in sanded soil

1.-Remove sand and manure. 2.-Introduce the probe directly into the soil (add water if it is hard or dry). 3.-Introduce the probe vertically into the soil. If serious resistance is encountered, an auger

109

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

2.- Installation in sanded soil

SAMPLE-TAKING

POST-HARVEST MAINTENANCE

should be used, but of diameter inferior to that of the capsule. 4.-Using the fingers, pack down the soil around the probe until a good contact is achieved (the interface between soil and probe should be airfree).  Replace the sand and manure. 1.- Load the probe with solution from the soil (fill the probe twice, and disregard the first samples obtained) 2.- To control the osmotic potential (daily filling of the probe). To control the ions, the probe must be filled 24 hours before the following irrigation. 3.- Once the probe is loaded: if there is no waste from the solution (same method as collecting the samples), the valve is opened, the pump is connected, and a vacuum is created (up to -70 kPa) and the valve is closed. 4.- Collection of samples: after 24 hours. The valve is opened, the tube connected to the syringe is introduced, and the sample sucked out. This is then transferred to another receptacle. Finally, the valve is closed, to avoid allowing contaminants in. At the end of the cultivation season, clean with acid and store until the new campaign. Source: Lao (1998)

In reality, there is not much data available on optimum levels of nutrients in soil solution. Notwithstanding this, Lao (1998) indicates some average levels regarding the nutritive solution and that of the soil, by way of different nutritive parameters encountered in the cultivation of tomatoes by commercial enterprises in Almeria. These levels are set out in the following table.

110

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

Units pH

PROBE

SN/PROBE

5.99

7.83

0.76

dS m-1

2.4

2.9

0.82

Nitrates

mMol L-1

11.67

12.69

0.92

Ammonium

mMol L-1

1.59

0.69

2.30

Phosphates

mMol L-1

1.26

0.22

5.73

Potassium

mMol L-1

7.94

6.02

1.32

mMol L

-1

3.52

5.55

0.63

Magnesium

mMol L

-1

1.99

4.23

0.47

Sodium

mMol L-1

4.55

6.89

0.66

Chlorides

mMol L-1

4.79

7.34

0.65

Calcium

Source: Lao (1998)

As will be observed, the soil’s pH remains high, despite the acidic character of the nutritive solution. This is attributable to the enormous “plugging” capacity of the soil and it renders difficult the absorption of certain nutrients, especially micro-elements such as iron, manganese and zinc, during periods of high requirement or in adverse weather conditions (winter). With regard to electrical conductivity, this parameter undergoes something of an increase in the soil, related to the nutritive solution, owing to the accumulation of elements such as sodium, chlorides, calcium and magnesium. It is interesting to follow the evolution of the soil’s electrical conductivity by taking weekly extractions and measuring their values through a portable conductivity meter. In this way, we will know the osmotic potential (Ψo) by means of the following expression:

The sum of this potential and the matrix, which is given by the tensiometer (around -20 kPa), will basically give us the value of the soil water potential, which should not exceed certain values which depend on the crop concerned, and on the time of year in which we find ourselves, so that the xylem flow rate should not diminish too drastically. An increase in the osmotic potential will indicate a build-up of salts in the soil, and this could warn us of the urgent need for washing to counteract this, or an excessive application of some nutrient or other. Concerning nitrates, it is interesting to follow their evolution in the soil liquid with the aim of preventing their concentration from “exploding”, since this could cause excessive vigour in the crops (with a consequent negative impact on fruit formation, and vulnerability to attack by fungi and bacteria) and also cause water problems, both on the surface and in the underground reserves. This latter aspect is now of great importance, because of the pernicious effect it can have on human health and on the environment, and is forcing modifications in the

111

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

way irrigation is managed and fertilization is carried out, in order to adjust the dosages of water and nitrogen to meet the needs of the crops, as will be addressed in the final chapter. Phosphates are rapidly undermined in the soil and, thanks to this, appear in very low concentrations in the soil solution. This is why there is no logical reason for supplying high concentrations of this ion in the irrigation water. Similar results were also obtained by comparing the supply of phosphates in a continuous way in the nutritive solution, with a certain amount in the form of “superphosphate” as basal dressing. This renders questionable the present method of applying this element in the irrigation water. According to González (1991), it is useful to know the available levels of phosphorus in the soil by means of the Olsen Method, in such a way that, if the reserves fall below 9 parts per thousand, it will be necessary to boost the supply currently in train. If the level reaches beyond 25 p.p.t. the application needs to be reduced. If it is greater than 140 p.p.t. application must cease abruptly. With regard to potassium, this element is retained in the change complex and a reserve exists in the soil which keeps it at a fairly constant level of concentration in the soil solution throughout the cultivation season, despite the possibility of a reduction in supply in the final phase. Even so, given the great importance of potassium for the quality of the fruit, its supply should never be disregarded. Calcium and magnesium tend to accumulate in the soil solution, owing to their strong presence in the change complex, given the conditions of Almeria. It is frequently unnecessary to apply magnesium because of the levels present in the irrigation water. However, calcium tends to be present in a decomposed state, thanks to other ions in the water, so it is normal to apply it, in order to obtain a Ca/Mg ratio in the soil solution greater than 1 (if possible, 2), which will avoid problems due to antagonism. Sodium and the chlorides always accumulate, because they are absorbed in very small quantities by the crops. It is essential to avoid high concentrations, so that they cannot cause antagonistic effects on the other elements, for example Cl/NO3, Na/Ca or Na/K. This can be achieved by increasing the irrigation dosage and thus washing the soil surface, which is where most roots develop in “enarenado” or sanded soil cultivation. Definitely, the soil solution available to the plant is the fundamental parameter which characterizes the latter’s nutritive condition and it is principally through fertigation that we can adjust this solution. However, it is not possible to offer a generalized design for fertigation, since it will vary, case by case. Lao (1998) advises the following management of fertigation through the use of suction probes: a) Knowledge of the nutritive condition of the initial soil solution, obtained through the probes. By this means, the initial condition can be known, and the definitive nutritive solution can be established b) Corrections to the nutritive elements supplied to the nutritive solution by way of interactions with the soil (through analysis with the probe) and the crop. In the event

112

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

of nutritional imbalances, analysis of the soil solution must be repeated every 15 days until control of the mix, within appropriate ranges, is achieved c) Weekly tracking of the electrical conductivity of the solution, via the probe d) At the start of full production, thorough analysis of the solution must be repeated, in order to confirm that it is meeting acceptable levels

5 The problem of nitrates, and its relationship with agricultural activity Contamination of the aquifers by nitrates is a consequence of the leaching of NO3- from agricultural systems. The aquifers which receive drainage water from natural ecosystems have very low concentrations of NO3- (<5 mg NO3- L-1). Leaching of nitrates consists of the vertical transportation of dissolved nitrates in drainage water, and is associated with the agricultural use of nitrogen-based fertilizers, something which is common in farming by irrigation. Nitrate contamination of aquifers is a public health issue. Consumption of nitrate-rich water can cause the illness known as methaehemoglobinaemia, also known as “blue baby syndrome”, which affects small children. For this reason, there is now legislation which limits the concentration of NO3- in drinking water, the maximum allowed in the European Union (EU) being 50 mg NO3L-1.

Legislation governing nitrates in agriculture

The EU Nitrates Directive (Council Directive 91/676/CE of 12 December, 1991) establishes a maximum level of 50 mg NO3- L-1 in all subterranean and surface waters in the EU. When the concentration of nitrates exceeds this limit, the affected areas are designated “Nitrate Contamination Vulnerable Zones” (ZVN), in which “action programmes” must be adopted, aimed at reducing agriculturally-caused nitrate contamination. Approximately 40 % of the surface of EU-27 has been declared ZVN. The Nitrates Directive has been incorporated into the Water Quality Directive (Directive 2000/60/CE of the European Parliament & Council, of 23 October, 2000) which consolidates all matters related to the quality of natural water resources, and which has as its objective that water contamination shall be minimized by the year 2015. In Spain, this Directive has been implemented at Autonomous Community level. By the Decree 36/2008 of 5 February, 22 areas in Andalusia are designated vulnerable to contamination by nitrates originating from agriculture, and in Almeria these include the principal areas of intensive horticultural production. The Order of 18 November 2008 contains the action plans applicable to the ZVNs of Andalusia. Among the required practices is the determination of the quantity of nitrogen-based fertilizers (N for nitrogen) applied as part of expected production, the restriction of applied N in manure and the creation of an N register (calculation of applications of N to crops), listing this as “nitrogen-rich fertilization sheets”.

113

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

Agricultural practices which contribute to the leaching of nitrates

A high level of NO3- leaching is associated with excessive application of N fertilizers and the occurrence of run-off when irrigation goes beyond what is necessary for the crops. Thicktextured soils which drain easily, and climatic conditions in which torrential rainfall is frequent, together with crops cultivated in the open air, are the circumstances which favour nitrate leaching. Excessive N applications happen when the N applied to the crops clearly exceeds the possible extraction of N at harvest (NH4+ & NO3-). The “N supply” includes the N laid down in nitrogenous fertilizers, the mineralized N from manure and from organic N in the soil, plus the residual mineral N from previous crops. In greenhouse soil-crops in Almeria, run-off is associated with over-irrigation during the establishment period following transplanting, and high-volume irrigation during disinfection/solarization and pre-transplant irrigation (Thompson & colleagues, 2007). Overfertilizing with N is a consequence of implementing rigid programmes of fertilization, which generally fail to take account of other sources of N, such as intensive applications of manure (Thompson et al., 2007). Big losses of NO3- occur in substratum cultivation, because 20-30 % of the irrigation solution tends to run off.

8 Agriculture practices for optimal management of nitrogenous fertilizers In various studies, techniques have been developed for managing the irrigation of intensive crops with nitrogenous fertilizers, in order to minimize nitrate escape whilst optimizing yield and quality (Granados et al., 2007). In the first place, prescriptive management techniques fall to be considered, taking into account water volumes and application of N adjusted to the needs of the crops, arrived at via modelization, based on information from crops grown previously, under similar conditions. In the second place, corrective management is proposed, through the use of sensors which indicate the state of moistness and nitrate concentration in the soil during the cultivation of the crops (Granados et al., 2007). In 2006 a crop of peppers was cultivated at the Cajamar Research Centre ‘Las Palmerillas’. The prescription of irrigation needs was based on evapotranspiration in the crops (Fernández et al., 2001), and the prescription of N absorbed by the plant was founded on the “Nup” model developed by Granados (2011). For corrective management, tensiometers were used to maintain adequate soil moisture, and suction probes to maintain a constant nitrate concentration in the soil solution, as well as an adequate salinity level during the cultivation of the crops. As a result, the volume of the irrigation was reduced from 355 mm as per conventional treatment (MC) to 296 mm as a prescriptive-corrective treatment (MPC), producing a reduction of run-off of almost 50 % (Figure 1). The use of prescriptive-corrective practices in irrigation and the application of N suggest a reduction of 176 kg N ha-1 of applied N, which equates to some 35 % of applied N, via conventional treatment. The concentration of nitrates in the crop run-off, with improved treatment, was 8.5 - 12 mMol L-1, while under conventional treatment it reached 19 mMol L-1, and the amount of nitrate lost through

114

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

leaching was reduced very significantly, by up to 40 % as compared with conventional treatment (Figure 1). Considering the use of suction probes as a method of monitoring the level of N in the soil, the nitrate concentration in the soil solution stayed constant at 8 - 12 mMol L-1 throughout most of the growing period, while under conventional treatment it stood at 14 - 24 mMol L-1 (Figure 2). Fruit production, biomass and N absorption under prescriptive-corrective treatment were similar to that obtained by conventional treatment, indicating that concentrations of 8 - 12 mMol L-1 in the soil solution do not inhibit the development of crops, and that it is possible to adjust the supply of N to the needs of the crops, obtaining thereby an important reduction in the amount of nitrate lost to leaching. 140

250

-1

N-NO3 lixiviado (Kg N ha )

120

80 60

200

150

100

Volumen (mm)

100

40 20

MPC

0 17-jul

50 MPC

0 10-sep

4-nov

29-dic

22-feb

17-jul

10-sep

4-nov

29-dic

22-feb

Figure 1: Accumulated volume of drainage water & the accumulated quantity of nitrogen in nitrate leachate form (NO3 ) in the prescriptive-corrective treatment (MPC) and conventional (MC)

[NO3- ] (mmol L -1)

25 20 15 10 5 MC

MPC

0 17-jul

10-sep

4-nov

29-dic

22-feb

Figure 2. Concentration of nitrates NO3 ] in the soil solution at 15 cm depth, in the prescriptive corrective management (PCM) and conventional management (CM) treatments (MC = Corrective Management - MPC = Prescriptive Corrective Management)

115

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Fertirrigation

References FERNÁNDEZ, M.D.; ORGAZ, F.; FERERES, E.; LÓPEZ, J.C.; CÉSPEDES, A.; PÉREZ, J.; BONACHELA, S.; GALLARDO, M. 2001. Programación del riego de cultivos hortícolas bajo invernadero en el sudeste español. Almeria, Cajamar (Caja Rural Intermediterránea). GONZÁLEZ, P. 1991. La fertilización mediante el riego localizado. Curso Internacional sobre Agrotecnia del cultivo en invernaderos. FIAPA. Almeria. 223-247. GRANADOS, M.R. 2011. Lixiviación de Nitratos desde Cultivo de Invernadero en Suelo en las Condiciones de Almeria: Magnitud, Factores Determinantes y Desarrollo de un Sistema de Manejo Optimizado. Tesis Doctoral, Universidad de Almeria. GRANADOS, M.R.; THOMPSON, R.B.; FERNÁNDEZ, M.D.; GÁZQUEZ-GARRIDO, J.C.; GALLARDO M.; MARTÍNEZ-GAITÁN, C. 2007. Reducción de lixiviación de nitratos y manejo mejorado de nitrógeno con sondas de succión en cultivos hortícolas. Colección Agricultura, Fundación Cajamar, Almeria. LAO, M.T. 1998. Gestión del fertirriego de los invernaderos de Almeria mediante el uso de sondas de succión. Tesis doctoral. Escuela Politécnica Superior de Almeria. 241 pag. THOMPSON, R.B.; MARTÍNEZ-GAITÁN, C.; GALLARDO, M.; GIMÉNEZ, C.; FERNÁNDEZ, M.D. 2007. Identification of irrigation and N management practices that contribute to nitrate leaching loss from an intensive vegetable production system by use of a comprehensive survey. Agricultural Water Management, 89: 261-274.

116

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

Soilless crop management Juan José Magán Cañadas Cajamar Research Centre ‘Las Palmerillas’

Preparing and commencing cultivation

One aspect, of vital importance, that should be considered before commencing cultivation is the uniformity of the irrigation installation, especially in soilless crops, where the volume of substrate in which the roots are confined is very small, consequently a homogenous supply of nutritive supplement must be ensured with the aim of avoiding disparate crop development. In all cases the coefficient obtained through the corresponding evaluation must be around 95 % or more, and if not then a revision of the state of the drip-feeders, the hydraulic design of the irrigation installation etc. must be carried out. When a new substrate is to be used, in the first place, it must be laid in its final position, and for this, the natural slope of the land must be taken into consideration. The slope through the whole of the substrate sack should not exceed 1 %, especially when substrates that retain lowsurface-tension water, for example rock wool, are used in order to avoid the higher part drying out excessively. However, if using substrates such as perlite or coconut fibre, which retain water at higher tension, gradients of 2-3 % are acceptable. To avoid excessive inclination the crop sacks may be supported with racks or arranged perpendicular to the gradient. In this case, if the rows of crops must be placed favouring the slope one may opt for plantation at the extremes of the sack and establish paired lines. The bag of polyethylene, or sack, that encases the substrate, often has a small perforation to avoid splitting during transport. The sacks should be placed with this perforation at the top to enable perfect saturation of the substrate. The following step is to open the planting slots in the crop sack using a cutter or other method and the placing of the dripper anchors, or pegs, into the substrate. Then the sack must be filled with a nutrient solution. In the case of organic substrates that are compressed and will expand during saturation, as is the case with coconut fibre, it is important that the irrigation sessions are short, using water at the highest possible temperature so as to favour the expansion process. The optimum time for this is at midday when it is hottest. It is convenient for the substrate to remain in saturation for 48 hours so as to reach a high moisture level and develop good hydraulic properties to then enable the opening of drainage holes. This should be carried out in the lowest part of the sack to avoid the water becoming stagnant and causing a proliferation of radical pathogens. In substrates that may present problems through high water-retention, as can happen with coconut fibre, it is advisable to make openings along the length of the sack to help with drainage. Also when using this substrate it is convenient to measure the electrical conduction properties of the solution, given that there may be an excess of salts toxic to the crop (sodium chloride) which would need washing prior to planting.

117

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

In plantation, the root ball of the seedling is placed on or inside the substrate, depending on the type of material. So, for example, in mineral wool the transplanting tends to be in plugs of 7.5 x 7.5 cm of the same medium, protected by plastic, so that the plug is placed directly onto the surface and the corresponding dripper is attached. Once rooting has taken place the dripper should be adjusted slightly to avoid water flow being blocked by the roots. Normally the dripper is kept above the plug and does not tend to pierce the surface, except in the case of neck or crown rot, since in this way it is higher and the cone of hydration from the dripper is greater. In the case of loose substrates (perlite, coconut fibre, sand, etc.) different materials can be used in the seedbed, although use of a medium that retains considerably more water should be avoided so as to avoid excessive water retention around the base of the shoot. If plugs of rock wool enclosed in plastic are used, these are placed onto the substrate ensuring the closest contact possible, if it does not have a plastic wrap or comes with a perlite or organic root ball it should be placed into the substrate with the dripper alongside. This should be moved further away when the crop has rooted to avoid problems of neck or crown rot. In the cultivation of peppers the plant should be planted up to the cotyledons to promote the production of roots throughout the length of the hypocotyl to avoid formation of “elephant foot”. In the case of rock wool, this precaution has to take place in the seedbed so that when transplanting takes place, the hypocotyl of the seedling can bend and be introduced into the opening. If the root ball is placed onto the substrate it is possible to open the drainage holes after planting as there is more time for the saturation of the substrate. If they are to be planted, the holes must be made prior to plantation so that excess water can drain away. In either case, thorough irrigation is required after plantation has been carried out, in order to ensure the best contact between the plug and substrate and to ensure root anchorage. In easily germinated crops that grow rapidly, like peppers and beans, seeding is often carried out directly into the permanent substrate. Seeding takes place using the finger to make a hole for the seed in the moist substrate. The depth varies between one and three centimetres and should be less in winter than in summer as germination is slower and there is less risk of the substrate drying out. Once the seed is in place it is covered with substrate. This can be done with the same crop substrate but for this, but fine vermiculite is best. It hydrates well and offers little resistance to the seed germination. Of course, the added substrate must be adequately moistened. When the substrate is used for subsequent cultivation but not planting immediately after the crop finishes, and allowing a resting period, it is best to keep the substrate damp through weekly irrigation so as to avoid an excessive build-up of salts, especially in the small pores that become difficult to wash out. Prior to the next planting it would be advisable to disinfect the substrate with a biocide, washing it thoroughly afterwards so that the new crop is not affected.

118

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

Another alternative is to solarise the substrate during the time it is not in use. To do this, the whole length of the substrate sacks is covered with fine plastic, sealing the sides into the earth or tucking them under the sacks, then closing the greenhouse completely, for a period of 45 days, in order to reach the highest temperatures possible.

Irrigation management at the beginning of the crop

Irrigation management is one of the most important aspects for the correct development of the crop, especially in soilless crops. Bear in mind that this influences growth and root health, and that a good root base influences the optimum crop. To carry out irrigation management, however, is no easy task, providing the water that a plant needs in sufficiently small doses so as not to excessively exhaust the water content of the substrate whilst not overirrigation and causing root asphyxia or the development of phytopathogenic fungi. The initial objective is to attain the maximum colonisation of the substrate by the roots in such a way that almost all of the available volume is used. This should be achieved before a great deal of fruit setting has taken place, as from that moment, the photoassimilates generated are preferentially directed towards the fruit in detriment to the roots. Given that the roots show a predilection for the areas in which there is a greater availability of water (where aeration is not limited) and of low salinity, the greatest concentration of roots is frequently found underneath the dripper, while the area between the drippers is not well-colonised. In commercial crops it is normal to have three emitters providing a flow rate of 2 or 3 L hˉ¹ per crop sack in order to reduce the installation cost. However, this leaves an excessively large separation between the drippers (50 cm), so important gradients of moisture and of electric conductivity tend to originate and impede the optimum colonisation of the substrate. The current tendency in Israel is to reduce the distance between emitters (to around 20 cm) and to use very low flow drippers (less than 1 L h-1) which allows a micro-irrigation system to be established keeping the substrate moisture level stable. When sowing directly into the definitive substrate, assuming that well hydrated substrate is being used, irrigation should not take place during the germination period as this can encourage fungus development, except if the substrate dries out excessively and the seed may be in danger of perishing. From the appearance of the first true leaves, normal irrigation can begin, although a certain amount of restraint tends to encourage abundant root development, which will be a key factor in meeting the crop’s increasing demand for water and nutrients. In the first few days after planting, given that the crop has still not taken root and is susceptible to water stress, it must be irrigated daily, so that there is a surplus input of water. When the transplanting is done in a rock wool plug and this is placed onto the crop sack, it tends to dry out quickly given that such material retains water at low tension. So, until the roots become embedded in the definitive substrate, they must be given small amounts of water several times a day, so that the plant always has easily available water. Once the roots emerge from the plug and become embedded in the substrate it may be better to restrict the irrigation, especially if the substrate is very moist, as this tends to encourage

119

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

radical development. However, at the time of carrying out this restriction, the excessive drying out of the substrate must be avoided, as this not only affects the crop in a negative way, but can also impede later adequate hydration of the substrate. This is especially important in rock wool which has limited capillarity. Another tactic that can help to colonise the substrate is to change the position of the anchor pegs of the emitters, although care must be taken with the possible displacement of the saline front. Another aspect of great importance that decisively influences irrigation management is the temperature of the nutrient solution. In summer crops low foliar area and extreme temperatures coincide and, given that the crop is still incapable of shading the irrigation pipes, the water inside them reaches very high temperatures (over 40 ⁰C) at midday and during the afternoon. In such conditions it is preferable not to irrigate as it could be extremely harmful to the roots. It is considered that, generally, root temperatures in excess of 30 ⁰C can be harmful, although they are better tolerated better when they are supported by a relatively low water content in the substrate. Therefore, irrigation would be restricted to late afternoon, evening and first thing in the morning when the temperature is not so high. As the crop grows, so do the water requirements, therefore we should increase the length of irrigation time, although limiting ourselves to the above-mentioned schedule. This may involve giving longer irrigation times in comparison to what would theoretically be correct from the point of view of substrate water retention, but it is preferable. When the crop reaches a certain size it is capable of shading the water pipes and, above all, the substrate. Thus it heats up less and it is then possible to water at midday. However, we should ensure that such irrigation is sufficient to guarantee that the solution that comes out of the drippers has come from the pipes outside of the greenhouse, which will be notably fresher than that in the interior irrigation sections. In this way, the average temperature of the solution provided is reduced. Also, longer irrigation times reduce the required number irrigation sessions and the average water content of the substrate. In winter planting cycles the situation is reversed and the temperature of the solution is low (below 15 ⁰C). In this case irrigation should be carried out at midday, when the solution in the pipes is warmer.

Subsequent irrigation management

After achieving a good colonisation of the substrate it is advisable not to limit the water supply to the crop, so that it develops rapidly and reaches sufficient vigour to ensure high productivity. Also, when the crop begins fruit formation it becomes more susceptible to water stress which can lead to deformed fruit, apical necrosis, etc. Therefore, if environmental conditions allow, it is advisable to irrigate frequently for short periods of time so that the water content of the substrate will be less drained and the roots will have easier access to water. Bearing in mind that the main limiting factor of the substrate for the absorption of water is hydraulic conductivity, which is the parameter that gives us an idea of the capacity of the substrate to carry water through its pores to the roots and thus to replace the solution absorbed from the vicinity of the roots. However, the hydraulic conductivity is not constant for a given material,

120

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

but diminishes as the moisture content reduces, such as can be observed in figure 1 for two different types of media used in Israel (RTM is a red tuff consisting of particles ranging in size from 0 to 8 mm and obtained through sieving the natural product, while RTB is a coarser version of the same size range, obtained from crushing larger particles and sieving the material through an 8 mm sieve (Raviv et al., 2002)). This is because, as it dries, there are more air-filled pores through which the water cannot circulate. The water is confined in small pores that have a greater specific area and consequently increased resistance to the circulation of water. A move in matrix pressure from 0 to 5 hPa can lead to a hundred fold reduction in hydraulic conductivity. For this reason, the water content in the substrate must only be allowed to fluctuate slightly in order to optimise the irrigation.

Figure 1: Hydraulic conductivity (Conductividad hidráulica) calculated versus suction tension, K(ψ), for types RTM and RTB media (Wallach et al., 1992; quoted by Raviv et al., 2002)

Theoretically, perfect irrigation should consist of supplying the nutrient solution to the plant drop by drop as needed, in such a way as to keep the substrate constantly moist. However, in practice this cannot be done, therefore, the aim is to cause the least possible fluctuation. Generally speaking, irrigation is justified when the easily available water has been depleted by 5 % as well as the reserve, which is the water content of the substrate retained at a pressure comprised between 10 and 100 c.c.a. (Martinez & Garcia, 1993). Conversely, it is necessary to apply an excess of water in relation to the absorption of the crop in order to avoid problems derived from the transpiration differences between plants, the non-uniformity of the irrigation and the accumulation of salts in the substrate. Even though water of excellent quality is used, a minimum drainage percentage of 15 % is advised for ease of management (Lorenzo et al., 1993). In field conditions this value tends to be increased by 20- 25 % for greater security. Logically, the worse the quality of the water, the greater the drainage must be to avoid exceeding certain levels of salinity in the substrate that would place limitations on the crop. These would depend on the species and variety involved, as well as the stage of development and the environmental conditions. There may be circumstances that could lead to 50 % of the water being discarded.

121

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

The volume of water to apply (V) will be the sum of the water depleted in the substrate (A) plus the excess that it is aimed to provide (L), so that:

The necessary leaching fraction (FL) is calculated according to the function of the most limiting ion in the irrigation water using the following expression (Gonzalez, 2001)

where: Cs is the concentration of the limiting ion in the nutrient solution Ca is the concentration of absorption for that ion, that is to say, the quantity of same absorbed for each volume of water absorbed and Cm is the maximum concentration allowed for that ion in the leaching

5 A

y = 0,068x + 0,83 2

y = 0,060x + 0,40

R = 0,99

R2 = 0,99

Concentración absorción Cl (mmol L -1)

Concentración absorción Na (mmol L -1)

Frequently, the most abundant salt present in the irrigation water is sodium chloride so the most limiting ions are sodium and chlorides. The absorption of both ions is not constant but tends to increase on a straight-line basis in its concentration in the root solution. Figure 2 shows the relationship obtained experimentally between both parameters for both ions in the cultivation of a long life tomato crop subject to different levels of salinity in the conditions of the greenhouses of southeast Spain.

0 0

60 0

Concentración Na (mmol L-1) Concentración Cl (mmol L -1)

Figure 2: Shows the relation between the average concentration of sodium in the recirculating solution and the average concentration of absorption of sodium (A) and between the average concentration of chlorides in the recirculating solution and the average concentration of the absorption of chlorides (B) in a crop of long life tomato in a greenhouse in the southeast of Spain (Magan, 2005)

As far as the maximum allowed concentration of limiting ion in the leaching is concerned, this will depend on the salinity level that the crop permits. The productive response to salinity follows that represented in figure 3. It shows that a plateau exists where the maximum production is reached. Below the electrical conductivity cmin a reduction of said production is

122

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

obtained owing to a suboptimal contribution of nutrients. In the same way, above the conductivity value cmax there is a linear decrease owing to saline effect. The maximum accumulation of harmful ions, without causing losses in production, is attained by keeping the salinity of the root solution close to this second value, but in such a way that the conductivity due to the nutrients be that which corresponds to the first threshold. Therefore, an accumulation of harmful ions will be admissible equivalent to the difference between both conductivities. In the case of sodium chloride, the relationship exists between the electrical conductivity owing to this salt (CE(NaCl)) and its millimole concentration in the solution (c(NaCl)) is, according to Sonneveld (2000): CE(NaCl) = 0.115 c(NaCl) (formula valid for a concentration lower than 50 mmol L-1 of NaCl). To be able to put this scheme into practice, it is necessary to determine experimentally the values of cmin and cmax. According to Sonneveld (2000), an electrical conductivity due to nutrients of around 1.5 dS m-1 may be sufficient to obtain maximum production in tomato crop. At the same time, in rose cultivation a value of 1.8 dS m-1 (from Kreij et al., 1997). However, said minimum necessary conductivity due to nutrients is going to be affected by growing conditions. Thus, when an abundant amount of nutrient solution is applied, as occurs in NFT, the root solution is frequently renewed resulting in lower than normal but admissible concentrations of nutrients. On the other hand, in conditions of low transpiration, the nutrients tend to be absorbed in greater concentrations, so the conductivity due to the nutrients must be greater in order to avoid their being drained in the rhizosphere (Sonneveld & van den Bos, 1995). It is obvious that this requires in-depth research to determine the value of cmin more precisely. As far as the maximum conductivity tolerated by the crop without loss in production and the down slope of production over said conductivity, these parameters are going to depend on the species in question and environmental conditions, meaning that they should be determined in the local area of cultivation. In experiments carried out with long life greenhouse tomato in the southeast of Spain, a threshold value of around 3.5 dS m-1 (Magán et al., 2008) has been achieved. Above this value, there is a linear reduction in commercial yield at a rate of approximately 8 to 12 %, for each unitary increase of conductivity depending on the experiment, although a gradual improvement in fruit quality is obtained. The optimum conductivity will depend on market demand.

123

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

Cosecha relativa

cmin

cmax

Figure 3: Effect of electrical conductivity (CE) of the root medium on the crop harvest (Sonneveld, 2000)

As the crop grows the absorption of water increases and the volume of leachate gradually diminishes if the supply is kept constant. Therefore, said leachate volume must be controlled from the beginning to avoid situations of deficiency. To do this, what’s known as a drainage tray is used, that allows the leachate to be collected from different representative areas of the crop, accumulating in a container to be quantified daily. At the same time as the excess water from the drippers is collected and, both volumes are compared, the drainage volume is calculated, which is a certain percentage of excess in regard to the supply. The aim is to keep this value close to the leaching fraction calculated theoretically, which will be corroborated through chemical analysis of the leachate solution. When the percentage of drainage measured is lower than it should be, it will be necessary to increase the frequency of daily irrigation. This increase will progress according to crop growth. The irrigation will have to be adequately divided throughout the day to adjust as much as possible to the water requirements of the plant, without excessive irrigation taking place or with limited drainage. In essence, the leaching should be uniform throughout the day. This type of programming is known as timing and tends to be used when plant are small. The crop water requirements are estimated based on the previous day’s and the forecasts carried out for the same day, and dividing them by the volume established for each irrigation session, the necessary frequency of irrigation is calculated. Finally the indication of start time of the sessions is programmed bearing in mind the previous comments. However, this system can lead to significant imbalances given that environmental conditions can vary greatly from one day to another. Therefore when the plant reaches a certain size, there is a tendency to use automatic controls which are much more precise. These will be discussed in the following section. In the same way as it is important to keep the hydration of the substrate at a level where the crop does not suffer water stress, it is also fundamental that there is sufficient volume of air (at least 25 % of the volume of the pores) so as to avoid root asphyxiation problems. If the airwater balance is inadequate (either too much or too little water retention), action must be taken to correct the situation with the irrigation system. So, shorter, more frequent irrigation

124

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

times if the substrate has dried out excessively, to promote its re-hydration and longer but further apart if too much water is being retained, whilst shortening the afternoon irrigation session to enable drying. During the winter, irrigation is conditioned by the low temperatures that reach the nutrient solution and the substrate to try to minimise their effect on root mortality. In view of this period it is worthwhile reducing the water content of the substrate, given that, reducing the transpiration levels of the crop, there is a lower risk of damage by water stress and the roots will tolerate the lower temperatures better. On the other hand, special care has to be taken when defining the active irrigation period during the day. In the morning, irrigation should not be started until the substrate temperature exceeds at least 12 ⁰C, as below this the roots show hardly any activity. Afternoon irrigation should finish early (at around 14 solar hours, although this depends on substrate water content) resulting in the partial draining of the water in the substrate ready for the temperature drop during the night. The aim is to achieve a reduction in water content of 5 % (or up to 10 % depending on the type of substrate) in such a way that there is no drainage obtained in the first irrigation of the following day. Although this implies a notable increase of the electrical conductivity of the root solution through the night, this is well tolerated by the crop. As well as reducing the risk of fungal attack at root level (especially Phytium). With this the root pressure can be reduced first thing in the morning, so there will be a lower probability of fruit splitting. On cold, rainy days it is advisable to stop the irrigation given that the evaporation is scarce and there is no problem in taking advantage of the water in the substrate. In crops where the quality of the product is determined by the content of soluble solids, such as melon or watermelon, it is advisable to restrict the irrigation during the week prior to harvest to obtain a greater sugar concentration. For this, drainage is reduced to a minimum so that the electrical conductivity of the substrate solution will tend to increase.

Automation of irrigation

When the crop reaches a certain size, and it becomes necessary to irrigate several times a day, it can be very useful to use automatically controlled irrigation systems that detect the consumption of water by the plant in real time and indicate the starting time of the irrigation in a set way. Without doubt the most popular system in Spain is the tray demand system. This incorporates a lateral gutter, or gulley, full of solution in which there is an adjustable regulator that sends an electric signal when it is out of the water and thus starts the irrigation. The plant absorbs the solution from the gutter through a hygroscopic blanket and in this way the water level lowers. It is, therefore, a direct control system. The tray demand system is a very useful and practical automatic system, even though the irrigation adjustment performance is not perfect. So, at times during the day of greater water demand (midday) a better drainage is achieved than in those with lower demand (in the

125

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

afternoon). As was previously mentioned, this situation is not ideal and for this reason, other irrigation systems have had to be used. The method of radiation is an indirect system given that it uses a pyranometer to measure the incident solar irradiation and the irrigation system is activated in correlation to this parameter. When a certain level of accumulated radiation is reached, which will already have been indicated to the programmer, irrigation begins and the meter returns to zero to begin another cycle. The problem with this method is that the correlation between radiation and crop transpiration is not perfect and, without considering other environmental factors such as temperature or vapour pressure deficit, that also influences said transpiration, significant imbalances throughout the day that are not tolerable in soilless cultivation. To avoid this problem, efforts have been made to improve the system of radiation by incorporating some modifications. One possibility consists of dividing the day into various periods and assigning a different accumulated radiation factor to each one. However, even though the adjustment throughout the day gives better results, a daily reprogramming of factors is necessary, as it is dependent on existing environmental conditions. Another possibility is the combination of pyranometer and an “intelligent” drainage tray, which would measure the leachate produced automatically by pulses. In this way, the programmer is capable of modifying, through adequate software, the factor of radiation and adjusting it throughout the day. The problem with this system is that it corrects the imbalances after they occur. Another very interesting method of irrigation system automation is the use of transpiration estimation models. They involve measurements in real time of the environmental parameters that influence this process and to integrate them in an adequate programme that is capable of calculating the transpiration of the crop. In this way, when a certain value that has previously been established as a set point is reached, the irrigation system is activated. This system can work very precisely but requires prior research so as to adjust the model to the exact location where it is to be used. It also requires the estimation of the foliar area of the crop and this can create significant imbalances. Other automated irrigation systems, such as the measuring of the matrix potential of the substrate through tensiometers, of the volumetric content of the water with FDR type sensors or of the transpiration of the crop with electronic scales can also be used in soilless cultivation, but at the moment these are less widespread than the previous systems.

Design of the nutrient solution

As the systems of soilless cultivation produce low inertia owing to the scarce volume of substrate in which the roots develop and that they frequently use materials with a low, or no, capacity of ionic exchange (rock wool, perlite, etc.) so it becomes fundamental to supply the mineral nutrients that the crop needs together with the irrigation water in the form of a nutrient solution. The adequate quantity and proportions of this input must be used to avoid possible deficiencies or toxicity and competition between ions.

126

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

As the concentrations of nutrient absorption by the plants are not the same as the existing ionic concentrations in the root solution, neither must they be so in the supply solution. These will be greater or less than in the root environment depending on the facility of the plant to take up each ion. So, for example, ammonia, phosphates or potassium which are easily absorbed ions, can be provided in a concentration inferior to the absorption concentration, which is going to reduce their levels in the root without affecting the crop and to reduce the losses through leaching. However, when the ions that a plant absorbs in a passive way or with difficulty as is the case with calcium, they will have to be supplied in a concentration superior to that of the absorption concentration so that they accumulate in the rhizosphere and “force” their way into the plant, thus attaining their maximum absorption potential. The concentration of each ion in the supply solution can be calculated mathematically with the following formula (González, 2001):

where: Cs is the concentration of the ion for which the calculation is carried out in the supply solution Ca is the concentration of absorption for this ion Cd is the concentration of the ion in the drainage FL is the fraction of leachate established R is the ratio between Cd y Cs The concentrations of absorption are not constant throughout the crop, but vary depending, mainly, on the development stage and the environmental conditions. It is recognised that these concentrations tend to diminish when the transpiration rate of the crop increases, so that the concentration in the supply solution must be reduced to avoid excessive accumulation in the drainage. This is why the solutions used in spring-summer are more diluted than those in winter. Furthermore, during the day there are also variations in the concentrations of absorption, proving lower at midday. To avoid an increase in the electrical conductivity of the root solution, it is advisable to use a more diluted solution at that time of day, even though the existing irrigation systems are frequently not prepared for this management to be carried out adequately. As far as the crop development stage is concerned, this also has a decisive influence on the concentrations of nutrient absorption. So, during the initial phase, the crop exhibits a substantial vegetative development for which the corresponding concentration of nitrogen is high. However, as fruit bearing advances, growth is reduced and the need for potassium increases, so the concentration of absorption of this element is increased and that of nitrogen is reduced. In figure 4 the evolution of the absorption concentrations of the different macronutrients is shown, in a greenhouse tomato crop in the southeast of Spain, transplanted in the middle of September and maintained until the beginning of June.

127

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

13 1,6 12 11

1,4

1,2

9 1 8

Concentración absorción Mg Concentración absorción K (mmol L -1) (mmol L -1)

7 8

0,8 3,5

7 3 6 5 2,5 4 1,3 3

Concentración absorción Ca Concentración absorción P (mmol L -1) (mmol L -1)

1,8

1,3 2

1,2

1,1 1,1 1

0,9

0,7 0,8 0,7

Concentración absorción S (mmol L -1)

Concentración absorción N (mmol L -1)

0,5 Oct Nov Dic Ene Feb Mar Abr May Oct Nov Dic Ene Feb Mar Abr May

Mes de cultivo

Figure 4: The evolution of the concentrations of absorption of the various macronutrients in a crop of long life greenhouse-grown tomatoes in the south-east of Spain (Magan, 2005). The straight arrows show the beginning of crop collection and the dotted arrows the harvest

In the case of nitrogen, its concentration of absorption initially reached high values (more than 13 mmol L-1) because of the substantial vegetative development of the crop. However, in November it suffered a sharp drop (around 10 mmol L-1) as a result of the increased burden of fruits and the deceleration of growth. It later began to recover, possibly because of the start of cropping and the reactivation of growth. From February onwards to the end of the experiment a progressive reduction in the concentration of absorption of nitrogen caused by an increase in the transpiration of the crop, the “tipping” and the subsequent lesser growth. This final reduction phase also took place for other nutrients such as phosphorous, potassium or sulphur. In the case of nitrogen, its concentration of absorption initially reached high values (more than 13 mmol L-1) because of the substantial vegetative development of the crop. However, in

128

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management November it suffered a sharp drop (around 10 mmol L-1) as a result of the increased burden of fruits and the deceleration of growth. It began to recover later, possibly because of the start of cropping and the reactivation of growth. From February onwards to the end of the experiment a progressive reduction in the concentration of absorption of nitrogen caused by an increase in the transpiration of the crop, the “tipping’ and the subsequent reduction in growth. This final reduction phase also took place for other nutrients such as phosphorous, potassium or sulphur. In the case of potassium, the evolution in the first months of cultivation was opposite to that of the nitrogen, so that it increased markedly in November in comparison with October as a consequence of the quantity of fruits present on the plant at the same time and their great demand for this nutrient. With regards the calcium, its corresponding absorption concentrations were quite stable during most of the experiment (around 2.5 mmol L-1), however in October they attained very high values (close to 3.5 mmol L-1) owing to the significant vegetative development, and at the end of cropping the values dropped to 2 mmol L-1. Conversely, the magnesium tended to increase throughout the experiment as a consequence of a certain build-up of this element; this was due to the fact that the crop was managed in a closed system and the concentration in the water was slightly higher to the absorption concentration. The drop in April could be due to the renewal of the re-circulated solution at the end of March and the increased transpiration of the crop. The ratio of the concentration of an ion in the drainage and its concentration in the supply solution (R) depends on the facility with which the plant is able to absorb it, as was previously mentioned. The relationship that usually occurs between both concentrations is shown in Table 1. With all of this information it is possible to calculate the required concentrations of the different ions in the supply solution. However, in southeast Spain there is already a certain amount of experience with soilless crops which enables a good approximation of the concentrations to which the different ions should be applied, to meet the needs of the species of horticultural crops in the area. In Table 2 the maximum and minimum values, between which said concentrations tend to oscillate, are indicated. The differences in the nutritive needs amongst species and varieties are not as great as one may think. Also, plants possess a great capacity for adaptation and frequently other factors are more limiting than those that are strictly nutritional, above all in the greenhouses of a passive climate in which environmental control is quite limited. The modifications that must be made to the nutrient solution are more important according to the stage of development than the horticultural species grown. In this sense, when cultivation begins, solutions with a high nitrogen concentration (12 - 15 mmol L-1) and calcium (4 - 5 mmol L-1) and a medium concentration of potassium (5 - 6 mmol L-1), tend to be used because of high vegetative development and the absence of fruits. Later, it is necessary to increase the potassium concentration (7 - 8 mmol L-1) to meet the demands of the fruits and to reduce that of the nitrogen (to around 10 mmol L-1) to avoid excessive accumulation in the drainage. As the crop develops, especially entering a period of greater transpiration, the nutrient solution will

129

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

generally need to be diluted to avoid an increase in the electrical conductivity in the drainage and the need to increase the leaching fraction to counteract it ION

Concentration in the supply solution

Concentration in the drainage solution

NO3-

100 %

75 - 125 %

NH4+

100 %

0 - 50 %

H2PO4-

100 %

50 - 75 %

K+

100 %

50 - 75 %

Ca++

100 %

125 - 200 %

Mg++

100 %

150 - 250 %

SO4=

100 %

150 - 250 %

100 %

+ 0.5 U

100 %

+1-2U

Table 1: The most usual relations between the ionic concentrations in the supply and drainage solutions in an inert substrate (Cánovas, 1998; Casas, 1999)

MACROELEMENTS ELEMENTOS

mmol L

MICROELEMENTS -1

ELEMENTOS

ppm

Nitrates

8 - 15

Iron

1 2

Phosphates

1-2

Manganese

0.6 - 1

Sulphates

1 - 2.5

Copper

0.05 - 0.1

Calcium

3.5 5

Zinc

0.2 - 0.5

Potassium

4-8

Boron

0.2 - 0.5

Magnesium

1 - 2.5

Molybdenum

0.04 - 0.05

Table 2: Ranges within which the concentrations of the different nutrients in the supply solutions used in southeast Spain tend to oscillate

When the percentage rates of leaching are high (40 - 50 %) to avoid excessive saline accumulation because of the poor-quality irrigation water, it is possible to slightly reduce the concentrations of the easily absorbed elements such as nitrogen, phosphorus or potassium and to thus reduce the conductivity of the solution. Furthermore, very high levels of potassium are not required since the high salinity provides sufficient quality to the fruits obtained (Cánovas, 1995) and the sodium acts as an antagonist of the potassium and replaces it in some of its functions in the plant.

130

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

Crop monitoring

It is useful to quantify the drainage produced on a daily basis and, at the same time, to measure the electrical conductivity and its pH, as well as that of the nutrient solution used, the imbalances of which with regard to the set values introduced in the irrigation programme indicate the existence of some anomaly in the irrigation rig that will need correcting; (inadequate calibration or poor state of the electrical conductivity or pH probes, change of water quality in the irrigation system, mistakes in the preparation of the stock solution, etc). It is normal for the pH of the supply solution to be somewhat higher than the set value and this is because, with the neutralisation of the bicarbonates, carbonic acid is produced, which is unstable and is released into the atmosphere as CO2. However, at the time of the adjustment, it has not completely changed and when it does so afterwards the solution loses part of its acidifying effect and its pH rises slightly. Therefore, to achieve a final value of 6 - 6.5 another value of 5.3 - 5.5 is often indicated on the programmer. As regards the conductivity, there should be no important differences between the measured and set values. In the drainage, generally, the conductivity is above the value corresponding to the supply solution and this accumulation can become more than two units. However, depending on the species that it concerns and on the environmental conditions, a maximum conductivity value in the drainage will be set, and must not be exceeded, in order to obtain acceptable production levels. If it is greater, it will then be necessary to increase the percentage of leaching or to modify the supply solution, reducing the nutrient concentrations. Although it happens less frequently, there are times in which the drainage conductivity is lower to that of the supply. This happens when good quality water is used and the crop is in the initial development stage; rapid growth and high concentrations of absorption occur. Regarding the drainage pH, this can be higher or lower than that of the supply depending on the ionic balance of the solution absorbed by the crop. In this way, if a greater absorption of anions than cations are produced, a net absorption of H+ consequently the pH of the radical medium rises. On the other hand, if more cations than anions are absorbed, H+ will be liberated and the pH will be lowered. The first situation is typical of young crops with rapid growth as they absorb a lot of nitrates. To compensate for this the nitrogen, in the form of ammonia, should be added to equalise the balance between the anions and cations. The second situation is typical of maturing crops in as much as the potassium absorption is high while that of the nitrates is low because of the limited growth, and become critical when very low pH values are reached (at around 4), as sometimes occurs with melons. To counteract this it will become necessary not to add ammonium (except that which is present in calcium nitrate), raise the pH of the supply solution and sometimes resort to increasing the buffering capacity of the solution by adding potassium hydroxide or potassium bicarbonate. With regard to chemical analysis, it is advisable to analyse the supply and the drainage solutions together because, at times, abnormal values are produced in the latter owing to an error in the former, as a consequence of an imbalance in the injection of fertilizers, in the

131

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

preparation of the stock solution, etc. Additionally, if it is suspected that the composition of the irrigation water has changed, this should be analysed to restructure the fertilizer. The drained solution should be analysed every month to check that crop behaviour matches our forecasts, or conversely, if it shows an absorption of nutrients different to that which was initially perceived. This check will be carried out taking into consideration the nutrient supply solution and the normal behaviour of the different ions, that which is expressed in Table 1. Based on these references, if the concentration of a certain ion in the drainage solution appears to be excessively low or high, the nutrient supply solution will have to be adequately modified. It is especially important to carry out a test during maximum cropping since, as was previously stated, the absorption of nutrients changes substantially during this phase. Additionally, this should also be carried out if any nutritional deficiency appears. In such a situation, a foliar analysis could be very useful to complement the information. At times it is possible to notice problems in the plant’s development that cannot be detected through chemical analysis of the nutrient solution. These errors are due to root or environmental problems that lead to nutrient absorption anomalies, even though said nutrients are present in the solution in the correct doses (Cánovas 1995). Therefore the crop will need to be closely observed so as to rapidly detect the possible changes that may take place and correct them in time. It is especially important to control the substrate hydration levels because, if they are too high, root oxygenation problems can arise leading to them dying off, and, conversely, if they are too low, the plant may suffer a water deficit which will have severe repercussions on the performance of the crop.

References Cánovas, F. 1995. Manejo del cultivo sin suelo. En: El cultivo del tomate. F. Nuez (Ed.) Ediciones MundiPrensa. Madrid. 227-254. Cánovas, F. 1998. Gestión de riegos y fertirrigación en invernadero. En: Tecnología de invernaderos II. Curso Superior de Especialización. J. Pérez-Parra; I.M. Cuadrado (Ed.) Editado por la Consejería de Agricultura y Pesca, F.I.A.P.A. y Caja Rural de Almeria. Almeria. 237-250. Casas, A. 1999. Seguimiento analítico de los cultivos: características de la zona que condicionan la solución nutritiva. Ajustes específicos. En: Cultivos sin suelo II. Curso Superior de Especialización. M. Fernández; I.M. Cuadrado (Ed.) Editado por la Consejería de Agricultura y Pesca, F.I.A.P.A. y Caja Rural de Almeria. Almeria. 267-286. de Kreij, C.; Voogt, W.; van den Bos, A.L.; Baas, R. 1997. Voedingsoplossingen loor de teelt van roos in gesloten teeltsystemen. Proefstation voor Bloemisterij en Glasgroente, Brochure VG 4, 35 pp. González, A.J. 2001. Balance de concentraciones en cultivos sin suelo. Aplicaciones. Editado por el Instituto de Estudios Almerienses de la Diputación de Almeria. Almeria. 147 pp. Lorenzo, P.; Medrano, E. y García, M. 1993. Irrigation management in perlite. Acta Horticulturae, 335: 429-434.

132

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Soilless crop management

Magán, J.J. 2005. Respuesta a la salinidad del tomate larga vida en cultivo sin suelo recirculante en el sureste español. Tesis doctoral. Universidad de Almeria. 171 pp. Magán, J.J.; Gallardo, M.; Thompson, R.B.; Lorenzo, P. 2008. Effects of salinity on fruit yield and quality of tomato grown in soil-less culture in greenhouses in Mediterranean climatic conditions. Agricultural Water Management, 95: 1041-1055. Martínez, E.; García, M. 1993. Cultivos sin suelo: hortalizas en clima mediterráneo. Ediciones de Horticultura. Reus. 123 pp. Raviv, M.; Wallach, R.; Silber, A.; Bar-Tal, A. 2002. Substrates and their analysis. En: Hydroponic production of vegetables and ornamentals. D. Savvas; H. Passam (Ed.). Embryo publications. Atenas. 25101. Sonneveld, C. 2000. Effects of salinity on substrate grown vegetables and ornamentals in greenhouse horticulture. Tesis doctoral. Universidad de Wageningen. 151 pp. Sonneveld, C.; van den Bos, A.L. 1995. Effects of nutrient levels on growth and quality of radish (Raphanus sativus L.) grown on different substrates. Journal of Plant Nutrition, 18(3): 501-513. Wallach, R.; da Silva, F.F.; Chen, Y. 1992. Unsaturated hydraulic characteristics of tuff (scoria) from Israel. J. Amer. Soc. Hort. Sci., 117: 415-421.

133

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses?

Waste, or products with other qualities and different uses? Sevilla, A.; Domene, M.A.; Uceda, M.; Buendía, D.; Racero, J.L. Cajamar Research Centre ‘Las Palmerillas’

Summary

Intensive greenhouse agriculture works along lines similar to industrial production, with a constant consumption of various resources, regular output of fruit and vegetables and, in consequence, the build-up of rejected matter. This includes various inorganic materials such as plastics or metals - and above all, an organic element which encompasses plant prunings during cultivation, the plant when it is uprooted and those fruits which are not offered for sale. The list of these leftovers has evolved from being a pile of waste susceptible to no treatment other than transfer to landfill, to a recyclable product. Practically all of this so-called waste now forms part of new processes which give value to rejected materials, and reintroduce them to the productive cycle at another level. This article will give an overview of the type of materials generated at each stage and summarizes the ways of giving new value to the various materials, paying special attention to the organic element, and the compost-based solution put into practice in the Cajamar Research Centre ‘Las Palmerillas’.

Breakdown of products generated by a greenhouse

Intensive agriculture has a work structure comparable to that of an industrial process. It uses a renewable resource, solar radiation, as its raw material, another series of natural resources such as the soil and rainwater and a number of inputs (fuels, fertilizers, pesticides, phytosanitary products, plastics, substrates, etc.) in order to produce consumable items such as fruits, vegetables or flowers. The process brings with it waste products in liquid form (leachates, fertilizer and phytosanitary residue), as well as other inorganic solids (trays, containers, underlay, soil, batteries, sanitary materials) and the most voluminous of all; organic waste generated during plant growth and the pulling up of the crop. One difference from the industrial process is, the final product can itself become part of the waste. Depending on the way the cultivation process develops and the state of the market, it can be the case that a part of or all the crop has to be destroyed, significantly increasing the waste-generation problem.

134

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses?

Scheme 1: scheme of the flow of resources and waste production for one hectare of an “AlmeriaType” greenhouse pepper crop

While the above diagram gives an overall idea of what happens in a greenhouse devoted to pepper cultivation, when it comes to recording the “waste audit”, it is necessary to concentrate on the day-to-day detail since the broad terms “plastic” or “organic material” conceal a wide diversity. Assorted products which come under the same heading can be very different in terms of their chemical composition or in their state of decomposition, and may require very different solutions. WASTE TYPE Rejected fruit Vegetable

Pruning End-of-Season Vegetable Waste

Laminated Plastics

Plastic greenhouse covers Anti-insect mesh Shading mesh Polypropylene string

Plastic Containers

Plastic phytosanitary containers Plastic fertilizer containers Plastic bags

COMMENTS Recyclable, problems of frequency & composition Recyclable Recyclable with problems - some items come wrapped Recyclable Recyclable Recyclable Recyclable with problems - difficult to handle Recyclable Recyclable Recyclable

135

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? Irrigation Pipes Substrates

Plastic Supports for Plants

Various

Sprinklers Rock wool Coco fibre Perlite Polystyrene trays Plant trays Plant pots Wire Wooden stakes Insect traps Pollination hives

Recyclable Difficult to recycle Recyclable Difficult to recycle Recyclable Recyclable Recyclable Recyclable Recyclable Recyclable Recyclable

Table 1: types of Waste Produced in a Greenhouse

Another filtering method which can be used when it comes to evaluating waste is the level of quality or the degree of contamination present in what is collected. Vegetable waste, which is the largest in terms of volume, is very diverse. Plant pruning which takes place throughout the growing phase produces very tender waste and is free of any kind of contamination, and which is different from that produced at the end of the growing cycle. In the former case, apart from a much higher quality, it provides a frequency and quantity which is more or less consistent throughout the cycle. In the latter case, the waste is produced once only, and in a matter of days. Under the heading of plastics, the vast majority is plastic greenhouse covering material, which is polythene and which is replaced every two or three years. However, other plastics such as trellis raffia, fertilizer containers, bags and trays are consumed at an annual rhythm. Their chemical make-up is always different from that of the plastic greenhouse covers, and always tends to contain traces of other chemical products.

Re-using byproducts - a theortetical framework

3.1 Plastics Products which become part of the greenhouse growing cycle leave with other properties and qualities which, if they cannot be returned to their original use, may require a less demanding level of quality for another. The following study sets out both the product’s problems, and possible new uses. 3.1.1 String (raffia) Polypropylene string used universally to support plants as they grow in height and lack the strength to support their fruits. The quality which has led to the widespread use of polypropylene string is its resistance to breakage.

136

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? However, ultraviolet radiation severely affects this property in such a way as to limit recycling options for producing an item with the same purpose. However polypropylene is a plastic with properties which have been studied in depth, as an attractant of certain hydrocarbons and as structural reinforcements for composites. In that case, the value of the product lies in the state of the microfibres, which is what reduces the problem caused by the string currently in use. Among the applications which have passed through the laboratory trial stage, the manufacture of concrete additives which improve some of the concrete’s properties can be mentioned, along with the development of absorption and containment barriers for oil spills, or the creation of new “cold” asphalt mixes. Under normal conditions, this solution for paving is one of the cheaper options, but its quality is lower than that of the high-temperature process. Notwithstanding, some tests in which polypropylene fibre has been added to the “cold” mix have improved the performance of the “cold” asphalt. The regular use of regenerated string, for whatever industrial application, entails a cleaner product than that which is currently used in. When the farmer harvests the crop, he picks up the vegetable material tangled with the string, creating a hybrid product consisting of both string and organic material which is useless, neither the string nor the organic product can be used. 3.1.2 Plant pots Plant pots are usually made of polypropylene which has a similar appearance to that of string, save that it comes in laminates, not as twine. This difference is important, because the twine form is much more complicated to process. It invariably “chokes” the cutting systems and has no axes, and it usually ends up stopping even the most powerful cutting apparatus. Plant pots, on the other hand, lend themselves to easy cutting and allow the production of polypropylene pellets as small as required. Once washed and disinfected, the pellets can be used to make broom handles, other plant pots, bicycle racks and a multitude of other plastic products. 3.1.3 Covering plastic In its totality, this plastic is polyethylene with additives to reduce its degradation under ultraviolet radiation, and to extend its useful life. The polyethylene is removed from the greenhouses every two or three years and retains its original chemical composition, plus traces of the chemical components which have been applied during the cultivation process and have clung to the inner surface. It also contains the remnants of the whitewash which is generally used in summer as a shading system. The washing of this plastic is straightforward and the resulting material is ground until acheiving a polyethylene pellet of similar characteristics to those of the pellet which produced the original material.

137

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? Recycled polyethylene pellets are widely used in the production of many polyethylene plastics not used in contact with foodstuffs such as bins, wheels, garden fencing or conglomerates.

3.2 Metals When it comes to the end of its working life after about fifteen years, the greenhouse frame (which is, in the vast majority of cases, a round or cubic structure of heat-galvanized steel) is recycled in its entirety as scrap metal, and goes back into the steel production cycle.

3.3 Incineration The best scenario we can hope for is the reintroduction of the plastic or the organic material in some other process which creates a useful product and avoids the consumption of raw materials. However, within the context of this optimum model, a proportion of these materials cannot be processed and will become waste. The plastics used in all packaging and the string are petrochemical derivatives and, as such, form a combustion fuel with very good properties when used in isolated form and will improve the condition of certain mixtures when other depleted organic material is added. In some cases, incineration offers the significant advantage of generating electricity, but has the contradictory drawback of being a potential source of noxious emissions. All plastic products, when broken down, present some type of contamination, so incineration has to be carried out under maximum measures of control. Fortunately, both incineration and gasification are highly-advanced processes and it is accepted that we can carry out the separation and cleaning of the entire product in a foreseeable way, just as control of bonfires and cleanliness of gas emissions can be completely guaranteed. The list of nations which have adopted incineration as a normal practice in the management of agricultural products includes the greater part of the so-called European nucleus. Holland, France and Germany, for example, use incineration for the management of both solid urban waste and by-products of agriculture.

The practical example of organic matter: compost production

4.1 Introduction to the process of composting The most widely accepted definition of “composting” is “the aerobic biological decomposition of organic waste of different origins, under controlled conditions, in such a state that we can manage, store and apply it easily and safely to the land, without adversely affecting the environment”.

138

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? It is known as decomposition rather than stabilization, because we cannot always guarantee that the stabilization of organic material will be complete. It is said that decomposition is of a biological/micro-biological nature to distinguish it from physical or chemical breakdown. We say that it is aerobic because oxygen is allowed to enter into contact with the material during the process. Therefore, according to the aforementioned the process is:  



Bioxidative, and therefore biological, which differentiates composting from other treatments of the physical or chemical kind, being an eminently aerobic activity Controlled, which indicates the necessity of monitoring and control of parameters while it is underway, distinguishing it from uncontrolled natural processes. Some of the parameters are temperature, humidity and oxygen supply. Takes place in the organic substrate in the solid phase. These are usually heterogeneous, and act as a physical support and a matrix for exchange, a source of nutrients and water necessary for metabolism of the micro-organisms. It supplies endogenous micro-organisms, retains the metabolic residue generated during development and acts as a thermal insulator for the system.

In principle, all organic material is susceptible to conversion into compost. We can take organic waste, from both fruit-growing and gardening, by-products from crop handling and processing. We can even consider waste generated by such diverse agrarian industries as olive presses, vineyards, etc.

4.2 Types of crop waste, frequency, quantity, quality and problems The quantity of vegetable waste which a greenhouse produces is linked to the product being grown, and to the rotations undertaken during the season. In accordance with the data compiled by the Cajamar Research Centre ‘Las Palmerillas’ team, the average farmer’s strategy is to cut the plant down to the roots or leave it to dry, in such a way that its original moisture content diminishes to almost half. The possible extremes between maximum moisture content at the moment of withdrawal from the greenhouse and the forced drying of the plant indicate a very important weight difference.

139

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses?

Graph 1: quantity of waste generated per hectare at the end of a long-cycle cultivation period

Graph 2: estimated distribution of vegetable waste generated in the province of Almeria, based on the type of growing cycle

The calendar governing the generation of waste is tied to the cycles of production of the different crops. Tomatoes, peppers and aubergines are considered long-cycle crops, while cucumbers, courgettes, green beans, melons and watermelons are short-cycle. When cultivating short-cycle crops in the greenhouse, it is common practice to introduce rotations within the one season, representative examples being peppers - watermelons, peppers melons, cucumber - watermelons and cucumber - melons (García, 1987). The cultivation process produces waste throughout the whole year in the form of pruning, removal of leaves, or the elimination of some fruit during grading and there are peak periods in January - February and May - June. The first peak corresponds to the end of the crop planted in the autumn (mainly beans, courgettes and cucumbers), and accounts for 19 % of the

140

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? vegetable waste. The May-June peak coincides with the end of the Spring planting growing period (mainly melons and watermelons), and the culmination of the long-cycle season or single crops, such as tomatoes, peppers and aubergines, representing 81 % of the waste (61 % being long-cycle waste, and 20 % being spring waste, respectively).

4.3 Composting solutions Container composting is the system where the organic material which we want to compost is placed in a container, silo or similar receptacle, capable of homogenizing the necessary conditions of humidity, aeration and the mixing of the components. In confined systems, the composting process can be kept under control, and the aerobic conditions can be kept optimum. The temperature of the stack can be managed more successfully and the leachates can be recovered. Humidity can be regulated and, in extreme circumstances, the gases emitted can be channeled. Those which are malodorous can be eliminated and, in appropriate cases, CO2 can be trapped, to avoid its dispersal into the atmosphere. Normally, these systems are associated with the use of rotation cylinders, designed so that the material enters through one “mouth”, and progresses towards the exit at a rhythm which is just what is needed for the thermophilic phase, in order to complete the first stage of composting. On its journey through the cylinder, the material is rotated, and this oxygenates and mixes it. Because the material is confined, its moisture cannot escape, and this can guarantee that the entire volume is preserved in identical conditions. Since the cylinder can be thermally isolated or sited inside a building, the outside environment does not affect the process directly, and the composting process is speeded up to the maximum possible biological rate. Additionally, the product emerges far better mixed and therefore much more homogenized than is achieved by traditional methods. It is possible to prepare the processing of enormous volumes in a continuous stream, producing compost of a carefully-controlled quality at a predictable rate. The advantages of this process have to be set against the economic cost. It is a process which requires a significant initial capital outlay, which consumes energy and which has operating and maintenance costs which need to be taken into consideration.

141

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses?

Scheme 2: schematic plan of the functioning of a rotational composting system Keys: Humidificación: humidification - Emision: emissions - Entrada de material: entrance for the material aireación forzada: forced aeration- Salida de compost: compost exit - Lixiviados leachates

Closed composting systems are opening up new possibilities, most of all when the problem which fails to be solved is complex or large volumes are involved. There are systems in existence designed to manage the entire solid waste of a whole city (Edmonton, Canada), or hospitals and social centres, to give examples of sites where efficacy counts above other considerations. However, the history of composting has been based on the management of open-air stacks with far more moderate technical requirements. Once the material is cut up or prepared for composting, the system requires no more than to stack the material in a “toblerone” pattern, one or two metres at the base, by one or two metres high. With this geometry, tractor-style machinery can be used, which can pass over the material, turning it to air and water it, to maintain the moisture content. Once the stack is formed, the manager needs to take into account that he will need to keep it going for a period of four to eight months. The simplicity of the system is balanced by the need for land. Not only do the stacks take up space, but when it’s necessary to turn the material over, which involves the machinery moving around. This requires an access network which is by no means negligible. The control of essential moisture can be achieved only on the basis of watering the stack if it dries out, but if at any given moment there is rainfall which paralyzes the composting process, the open-air method offers no way of controlling this. The lack of control over moisture and oxygen makes the process slower and means that less homogeneity will be achieved. In a stack, the materials decompose a little at a time, and it is difficult for them to mix together, and while the heart of the stack attains optimum conditions, the outer parts do not. If the materials can’t be mixed together thoroughly, the composting process will not proceed evenly throughout the whole of the stack. These uncertainties have become part of the composting debate, and in this context, composting has developed over the last three or four decades and has succeeded in reaching new levels, these being demanded both by the users of organic fertilizers and by public authorities, which have a duty to see that products meet standards of quality and hygiene.

142

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses?

4.4 Examples There are very many examples of small-scale composting, and many others of large-scale plants. The majority are fed with a mixture of solid urban waste, farm residue and domestic refuse. Facilities dedicated to the management of waste emanating from intensive greenhouse agriculture are not so common, but there are farmers who compost their own waste, as well as plants which undertake the work of an entire zone. One of these examples is that developed by the Cajamar Research Centre ‘Las Palmerillas’ which has been carried out not only due to the proximity but also because it is designed to manage the waste that a one to two hectare plot can produce. The rotational composter model uses a three-metre long, one-metre diameter cylinder with an initial load of about 200 Kg. The cylinder has some blades inside, and a motor powered by solar energy, which turns the drum at the rate of 1 rpm. The composter is loaded to capacity, and the carbon-nitrogen ratio is balanced by adding sawdust. A little water is also added, in a quantity which stabilizes the condition of the material for the start. Products such as tomatoes tend to be greener and moister than peppers or aubergines, which are woodier and give the mix a drier consistency. Once the composting process is under way, the mix is maintained at between 60 and 70 ⁰C, and the volume reduces. To ensure that the process isn’t halted, more material is added on a weekly basis for the following two or three weeks, when the thermophilic phase has started. The motor starts up during the middle hours of the day in the early stages, and once the compost has cooled, it is switched off, and used only once or twice a week after that, merely for stirring the mix.

Image 3: rotational composter, designed by Cajamar Research Centre ‘Las Palmerillas’

After six or seven weeks, the stack drops in temperature to around 40 ⁰C and then the mix is removed from the composter and piled up. The composter cycle begins anew and during the course of a season the process will be repeated from three to six times, piling all the material extracted in the same place, and allowing it to mature.

143

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? The advantage of this set-up over the stack is, compost can be made with relatively small quantities of product, which will be suitable for small farms, or for managing compost during the pruning or thinning-out period, when material is becomes continually available, but in small quantities. The composting of a large farm, including the waste from the end-of-season harvest, was undertaken for the first time in 2010, using a “flexible” stack. The most obvious reason for this was, in a matter of weeks, a big farm produces dozens of tonnes of organic waste, with a useful life as potential compost of no more than a fortnight. This leads the farmer to use a flexible stack, because it is a quick method and can cope with large volumes economically. To ensure the quality and rapid compost production, we proceed to chop up the vegetable matter with a rotovator hitched to a tractor. In this process, the volume decreases by about 70 %, which allows the preparation of stacks around 2 x 3 metres, with a starting height of 1.5 metres. Just as with the rotational composter, the stack is stabilized with sawdust, paper waste, or leaves, in order to fix the appropriate amount of carbon. It is then watered. As opposed to the composter system, the stack loses moisture more rapidly and this has to be replaced with very frequent watering during the thermophilic phase. In our case, the stacks are situated under a roofed structure which contains an automatic “sprinkler” watering system which, in the summer, is activated almost daily. The difference between the rotational composter experience and that of the treatment in stacks is, in the latter case we were able to handle the total waste generated on the more than four hectares of cultivated land available to the Research Centre, such that material started to be collected in May and this concluded in June, with the collection of the last crops.

Scheme 3: stack composting progress - carried out in the summer of 2011

4.5

Ways of measuring the quality and suitability of the product

The quality requirements relating to compost are aimed at achieving: acceptable appearance and aroma, correct hygiene treatment, impurities and contaminants kept to trace levels, known quantities of components which are agronomically useful, and characteristics which are

144

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? homogenized and uniform, so as to permit storage without having to go through subsequent alterations. The regulatory bodies lack the coordination of those which govern traffic, and there is no single universal definition beyond aspects related to the guarantee of health. Assuming that pathogen control is set, at least, in accordance with the Royal Decree 824/2005 of 8 July, regulating fertilizer products: Order APA/863/2008. of 25 March, (Salmonella Absent / 25 g product, Escherichia coli: < 1.000 NMP/g product, these being contained in the Royal Decree 2071/1993 of 26 November, in the Law 43/02 regarding Vegetable Safety, Order 776/02 of MAPA), the measures of quality presented in the following table are a synthesis of the requirements published by some of the international associations devoted to compost, or regulatory bodies governing composting. Measurements are generally grouped in three parameters: PARAMETER Physical Particle size distribution Apparent density

Inert material

% Moisture content

IDEAL VALUE

COMMENTS

Able to pass through an 8 mm sieve can vary 25 %, according to initial product or state of maturity Can include up to: · 5 % stones/sand · 3 % plastics/metals

600 Kg m-

<8%

always above 30 %, even in very mature composts

40 - 50 %

Chemical pH

Electrical conductivity

C/N % Organic matter

Determined by the original material. Tends to be basic if consisting of leaves and more acidic if mixed with manure

6.8 - 8

-1

3.5 - 6.4 mS m

Indicates the amount of soluble salts. Among them are chlorides and sulphates which are harmful to plants. The optimal threshold is determined by the proposed end use. Delicate plants or seedlings will not accept values greater than 2.5, while many others thrive on values of 6

10 - 14 % 35 - 70 %

% N (total)

1 - 2.5 %

% P (P2O5) %K % Ca

1.5 - 2 % 1.5 2

This is the sum of inorganic nitrogen in the form of nitrates, and the organic nitrogen embedded in the organisms present. Not all of this is available to plants via direct assimilation

145

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? PARAMETER % Mg Heavy Metals Arsenic Cadmium Copper Níckel Lead Zinc Mercury Selenium Chrome (total ) Biological Total Bacteria Actinomycetes Fungii Nematodes Maturity index

IDEAL VALUE 1 - 1.3 % -1 (mg kg in soil) 41 2 300 90 150 500 1.5 100 250 -1 (UFC g ) 7 133·10 4 41·10 3 48·10 absent > 95 % germination

COMMENTS

Many plants can be heavy metal tolerant, and for this reason limits are established in order to avoid problems within the plant, as much as to prevent them passing into the food chain These values may be reduced if the original material is rich in any one of these elements

Of the different measurement systems, we mention seed germination in radishes or grass

References Allen, E.R, Ming D.W. Recent progress in the use of natural zeolites in agronomy and horticulture. In Ming DW, Mumpton FA (eds) Natural Zeolites’93 Occurrence, Properties, Use. Int’l Comm Natural Zeolites, Brockport, New York (1995) 477-490. Barbarick, K.A., Pirela, H.J. Agronomic and horticultural uses of zeolites: A review . In Pond W.G, Mumpton, F.A (eds) Zeo-Agriculture: Use of Natural Zeolites in Agriculture and Aquaculture. Westview Press, Boulder, Colorado (1984) 93-103. Bremmer, J.M., Mulvaney, C.S. (1982). Nitrogen total. En Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, A.L. Page et al., eds, American Society of Agronomy, Inc Madison, Wisconsin, 595-624 Brown, K.H., J.C. Bouwkamp, & F.R. Gouin. 1998. The influence of C:P ratio on the biological degradation of municipal solid waste. Compost Science and Utilization, 6(1): 53-58. BOE 131/1998. 12731. Orden de 28 de mayo de 1998 sobre fertilizantes y afines. p. 18028 - 18078. Dan M. Sullivan & Robert O. Millar. 2005. Propiedades cualitativas, medición y variabilidad de los compost. P. 95- 119. En: Utilización de Compost en los Sistemas de Cultivo Hortícola. Ediciones Mundi Prensa. Dickson, N., T.L. Richard y R.E. Kozlowski. 1991. Composting to Reduce the Waste Stream: A Guide to Small Scale Food and Yard Waste Composting. Natural Resource, Agriculture, and Engineering Service (NRAES), Ithaca, New York. Federación Agroalimentaria de CC.OO., 2000. Formación para valoración de residuos agrícolas. 75 pp.

146

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? F. Madrid, R. Lopez, F. Cabrera, J.M. Murillo. Caracterización de los compost de residuos sólidos urbanos de la planta de Villarrasa (Huelva). Invest. Agr.: Prod. Prot. Veg. Vol. 16 (1), 2001 p. 105-117. Golueke, C.G. 1977. Biological Reclamation of Solid Wastes. Rodale Press, Emmaus, Pennsylvania, p.9. Hamoda, M.F., H.A. Abu Qdais, and J. Newham. 1998. Evaluation of municipal solid waste composting Kinetics. Resources, Conservation and Recycling, 23: 209-223. Inbar Y., Chen Y. & H.A.J. Hoitink. 1993. Properties for establishing standards for utilization of compost in container media, p. 668-694. In: H.A.J. Hoitink y H.M. Keener (eds.) Science and Engineering of Composting: Design, Microbiological and Utilization Aspects. Renaissance Publications, Wothington, Ohio. Kayhanian, M. & G. Tchobanoglous. 1993. Characteristics of humus produced from the anaerobio composting of the biodegradable organic fraction of municipal solid waste. Environmental Technology, 14: 815-829. Leggo, P.J. An investigation of plant growth in an organo-zeolitic substrate and its ecological significance. Plant and Soil (2000) 219,135-146. Mathur, S.P. 1991. Composting processes, p. 147-183. In: A.M. Martin (ed.). Bioconversion of waste materials to industrial products. Elsevier Applied Science, New York. McGaughey, P.H. & H.B. Gotass, 1973. Stabilisation of municipal refuse by composting, p.897-920. American Society of Civil Engineers Transactions. Proceedings-Separate N⁰. 302 Paper N⁰. 2767. Minato, H. Characteristics and uses of natural zeolites. Koatsugasu (1968) 5, 536-547. Ministerio de Agricultura, Pesca y Alimentación de España, 1986. Métodos Oficiales de Análisis. Vol. III. Madrid. Morisaki, N., C.G. Phae, K. NakasaKi, M. Shoda, y H. Kubota. 1989. Nitrogen transformation during thermophilic composting. Journal of Fermentation and Bioengineering, 1: 57-61. Pérez-Parra, J. J. y Céspedes López, A. J. 2001. Análisis de la demanda de inputs para la producción en le sector de cultivos protegidos de Almeria, p1-102. En: Estudio de la demanda de inputs auxiliares: producción y manipulación en el sistema productivo agrícola almeriense. Fundación para la Investigación Agraria de la Provincia de Almeria (FIAPA), Almeria. Richard, T.L. 1992. Municipal solid waste composting: physical and biological processing. Biomass and Bioenergy, 3 (3-4): 163-180. U.S. Environmental Protection Agency (U.S. EPA). 1992. Sampling procedures and analytical methods, p. 41-47. In: Environmental Regulations and Technology. Control of Pathogens and vector Attraction in Sewage Sludge. EPA/626/R-95/013. USEPA, Office of Research and Development, Washington, D.C. Finstein, M.S., and J.A. Hogan. 1993. Integration of composting process microbiology, facility structure and decision-making. cience and Engineering of Composting: design, environmental, microbiological and utilization aspects. Eds.: Harry A. J. Hoitinknd Harold M. Keener. Renaissance Publications. Ohio

147

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Waste, or products with other qualities and different uses? Keener, H.M., C. Marugg, R.C. Hansen, and H.A.J. Hoitink. 1993. Optimizing the efficiency of the composting process. Science and Engineering of Composting: design, environmental, microbiological and utilization aspects. Eds.: Harry A. J. Hoitink and Harold M. Keener. Renaissance Publications. Ohio.

148

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

Optimising the application of phytosanitary products in greenhouses Julián Sanchez- Hermosilla¹, Victor J. Rincón¹, Francisco Páez², Milagros Fernández² ¹ Dept. Engineering. University of Almeria. Campus of International Excellence in Food and Agriculture CeiA3 ² Institute for Agriculture and Fisheries Research and Training (IFAPA- La Mojonera). Junta de Andalucía

Introduction

The area devoted to the cultivation of fruit and vegetables in greenhouses, currently at around 29.990 hectares, has increased significantly in recent years (Cabrera & Uclés, 2012). This has allowed the province of Almeria to become one of the areas of greatest production of fruit and vegetables in Europe, reaching 2.973.614 tonnes in the 2011/2012 season (Cabrera & Uclés, 2012). The greenhouse based productive system used in south-east Spain, is characterised by highdensity cultivation and an environment with high temperatures and relative humidity. These conditions lead to a high incidence of pest infestations and diseases that are in greater part controlled by the use of chemical products. Nowadays the agrifood industry, and more specifically the fruit and vegetable sector, seeks the production of quality foodstuffs through safe, sustainable methods. This has given rise to the development and use of less aggressive methods where the integrated control of pest infestations is emphasised. Nevertheless, the use of phytosanitary products continues to be one of the most commonly used alternatives to satisfy the demands of the food market, consequently rational use of such is required, using less hazardous substances and efficient application methods. Along these lines are the European Directive on sustainable use of phytosanitary products (2009/128/CE), the Machinery Directive (2009/127/CE) and the Commercialisation of Phytosanitary Products Regulation (2009/1107/CE). That a treatment is effective does not necessarily mean that it is efficient, for it to be considered efficient, the application must be optimised, understanding by this, that it be carried out with correctly calibrated equipment, providing deposits close to the control threshold of the pest infestation or disease, uniformly distributed throughout the plant biomass, minimising losses, applying the least possible amount and guaranteeing the safety of the person applying it and the environment. There is a series of factors which determine the efficiency of a phytosanitary application, amongst which are: the application equipment, the type of nozzles used, volume of application and the working pressure. The influence of some of the variables previously indicated have been analysed, for phytosanitary applications in

149

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses greenhouses, within the projects “Rationalisation of the phytosanitary applications in horticultural greenhouse crops through a movable self-sustained platform” (AGL200500848/AGR) of the National Plan for Scientific Research and “Analysis and evaluation of application techniques for phytosanitary products in greenhouses. Reduction of environmental impact and techno-economical optimisation”.(P07-AGR-02995), financed by the Regional Government of Andalusia (Projects of Excellence). Some of the results obtained are shown in the following text.

The influence of application equipment

The application of phytosanitary products is mainly carried out through manual systems such as spray pistols or wands (shown in Fig. 1) This equipment is currently found in 91.7 % of the greenhouses in south-east Spain (Céspedes et al., 2009). Normally, with this type of equipment, the applications take place at high pressure (> 20 bar), with high volume distribution, until drop point is reached. They are characterised by low cost, ease of maintenance and they are adequate for the control of specific phytosanitary problems. However, the treatments carried out with this type of equipment show low-level efficiency, owing to low deposition and the lack of uniformity of the distribution of the phytosanitary product throughout the vegetation, high losses to the soil (Sanchéz- Hermosilla, 2011 & 2012) and elevated risk of exposure to those applying it (Nuyttens et al., 2009). Other types of application equipment exist that are used in lesser measure in greenhouses, such as the spray cannon and equipment supplied with vertical spray bars. The spray cannon (Fig. 2) is a piece of more technically advanced equipment than the spray pistols and wands. The main advantages of these are the time saved in application of the treatments and less exposure to them for those who apply them. However, these applicators are less effective than the spray pistols when working on staked crops with high-density vegetation, since lowuniformity distribution of the phytosanitary product is implemented within the cultivation lines as well as using greater volumes in application and producing significant losses into the soil (Garzón et al., 2000).

150

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

Figure 1: spray gun applicator

Figure 2: spray cannon

151

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses The apparatus equipped with vertical bars is characterised by two vertical spray bars with several nozzles on each one. They generally work at pressures of approximately 10 bar and use fan nozzles. The separation between the nozzles must be adjusted according to the working distance to the crop and the type of nozzle used. It is recommended to use a separation of 50 cm for nozzles with a fan of 110 degrees, since it has been demonstrated that the fan nozzles give better results than the cone nozzles (Sánchez- Hermosilla et al., 2003). Different types of apparatus equipped with vertical bars can be found, from the manual cart or trolley type sprayer (Fig. 3) to the more advanced models, amongst which the self-propelling units specifically designed for the application of phytosanitary products in greenhouses can be found (Tizona®, Fig 4). It is easier to control the operational variables such as working pressure and displacement speed on the latter-mentioned units, allowing more uniform spraying. There is also a stand-alone unit (Fitorobot®, Fig. 5) that carries out treatments without the need for an operator to be present and thus eliminates risk of exposure.

Figure 3: manual spray trolley

Figure 4: vertical bar equipment (Tizona®)

152

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

Figure 5: Fitorobot®

Another alternative for the application of phytosanitary products in the greenhouse is the use of nebulisation or fogging systems (Fig. 6). The main objective of this type is greenhouse climate control. It is made up of two networks of pipes, phytosanitary solution circulates at low pressure (2 - 3 bar) through one set of pipes, supplied from a tank, and through the other, air, at a pressure of (6 - 7 bar) ,supplied by an air-compressor. Spray nozzles are uniformly distributed along the length of the pipes. In these, the phytosanitary liquid and the pressurised air meet and cause division into fine droplets. The possibility of automating the process of phytosanitary application with these systems is their main advantage, since it can be carried out at the most opportune time, without the need for an operator inside the greenhouse. The drawback is, these systems give rise to a less uniform distribution of the phytosanitary product (Rincón et al., 2010), and to difficulty in achieving adequate deposits on the underside of the leaves and the internal area of the crop.

153

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

Figure 6: fog system a) Close-up of a spray nozzle b) Greenhouse interior during the fogging process

The influence of the nozzle type

Studies have been carried out with manual spray trolleys to evaluate the influence of the type of nozzle (Sánchez- Hermosilla et al., 2012), analysing the deposit over the crop and the losses into soil, comparing them to those produced with a spray pistol. The working conditions of the systems in the trials carried out are shown in Table 1. Application equipment

Spray gun¹

Nozzle type

Duple fan

Teejet XR 110 02

Albuz AVI 110 02

N⁰ of nozzles

Pressure (bar)

22.0

11.9

11.8

Volume of application (L haˉ¹)

1.564

1.593

1.630

Cart

¹ Application of reference (normally used by the growers in the area) Table 1: working conditions of the different systems

Between the two types of nozzles evaluated, standard fan and air induction fan, there were no significant differences found in the deposition onto the crop and the losses into the soil. However, the deposits were slightly superior using the standard fan nozzle. In both cases the

154

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses results obtained were better than those of the spray pistol, depositing up to 40 % more of the applied product onto the crop and reducing the losses to soil by 54 % (Fig. 7). It must also be taken into account that the trolley sprayer works at 45 % less pressure than that in the spray gun.

60 Deposición total

Total deposits

Pérdidas al suelo

Losses to soil

Deposición (µg cm-2)

Deposits (µg cmַ2)

Standard Fan Nozzle

Spray Gun

Air Induction Nozzle

0 BV-AS

BV-AI

Pistola

Figure 7: total deposits over the crop and losses to soil with the vertical bar equipment with standard fan nozzle, air induction nozzle and spray pistol

Influence of the volume of application

Studies have been carried out to determine the influence of the volume of application comparing manual carts with spray pistols (Sánchez-Hermosilla et al., 2011). For this purpose a reference volume with the spray pistol (P1600) was applied and a lesser volume with the same equipment (P900) and this was compared with the applications based on a trolley equipped with standard fan nozzles at three different volumes (1.000, 750, and 500 L haˉ¹) (Table 2). Application equipment

Spray gun

Cart

Type of nozzle

Double fan1

Fan2

Number of nozzles

Average pressure (bar)

Volume of application (real) (L ha-1) Trial code 1

865

1.666

524

767

1.048

P900

P1600

BV500

BV750

BV1000

Double fan NOVI ² Albuz API 110015

Table 2: Working conditions in the trials: Influence of application volume

155

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

In Figure 8 it is observed that there were significant differences between the treatments carried out with the spray pistol. The trial at lesser volume (P900) offered poor results, inasmuch as the 48 % reduction in applied volume lead to a decrease of 68 % in the deposits with regard to the referred application. These results reveal the applications with the spray pistol should take place at increased volumes. However, the results obtained with the vertical bars equipment show that similar deposits are obtained to those in the referred application (spray pistol at maximum volume, P1600), also using a 40 % reduction of volume (VB1000) the applications are more uniform and with less wastage to soil. The trials with vertical bars, at much lower volumes, (VB500 and VB750) provide deposits that greatly differ from those obtained in the referred application (P1600).

Total deposits

Deposición total

Pérdidas al suelo

Losses to soil

Deposición (µg cm-2)

Deposits (µg cmַ2)

0 BV 500

BV 750

BV 1000

P 900

P 1600

Figure 8: total deposition and losses to soil with vertical bar equipment (VB) at three different volumes (500, 750 -1 -1 and 1.000 L ha ) and with the pistol (P) at two different volumes (900 and 1.600 L ha )

Acknowledgements

This work has been financed by Bayer Crop Science S.L. and the Regional Government of Andalusia within the Project of Excellence P07- AGR-02995.

156

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Optimising the application of phytosanitary products in greenhouses

References Cabrera, A.M., Uclés, D., 2012. Análisis de la campaña hortofrutícola de Almeria. Campaña 2011/2012. Fundación Cajamar, Almeria. Céspedes, A.J., García, M.C., Pérez, J.J., Cuadrado, I.M., 2009. Caracterización de la explotación hortícola protegida Almeriense. Fundación para la Investigación Agraria en la Provincia de Almeria. Garzón, E., López. L., Sánchez-Hermosilla. J., Barranco. P., Agüera. L., Cabello. T., 2000a. Eficacia técnica de la aplicación de fitosanitarios con cañón atomizador. Vida Rural. 112: 44-48. Nuyttens, D., Braeckman, P., Widney, S., Sonck, B., 2009. Potential dermal exposure affected by greenhouses spray application technique. Pest Management Science. 65:781-790. Rincón, V.J., Páez, F., Sánchez-Hermosilla, J., Fernández, M., Carreño, A., Pérez, J., 2010. Characterization of a fog system used for pesticide application in greenhouse crops. Internacionational Conference on Agricultural Engineering. AgEng 2010. Clermont Ferrand (Francia) Sánchez-Hermosilla, J., Medina, R., Gázquez, J.C. 2003. Improvements in pesticide application and greenhouses. Workshop on Spray Application Techniques in Fruit Growing. Universidad de Turín, Italia. 54-61. Sánchez-Hermosilla, J., Rincón, V.J., Páez, F., Agüera, F., Carvajal, F. 2011. Field evaluation of a selfpropelled sprayer and effects of the application rate on spray deposition and losses to the ground in greenhouse tomato crops. Pest Management Science 67 (8), pp. 942-947. Sánchez-Hermosilla, J., Rincón, V. J., Páez, F., Fernández, M., 2012. "Comparative spray deposits by manually pulled trolley sprayer and a spray gun in greenhouse tomato crops”. Crop Protection 31 (1), pp 119-124.

157

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

Managing resistance to insecticides Pablo Bielza Lino Full-Professor - Department of Plant Production Superior Technical School of Agricultural Engineering - Polytechnic University of Cartagena

Introduction

In this chapter we will present a complete overview of the phenomenon of resistance to insecticides, from how occurs (mechanisms) to how to avoid it (strategies). This general overview will help us to understand cases of resistance for each pest considering resistance to insecticides is a common phenomenon. The objective of sustainable pesticide use is to reduce the risks and the effects on human health and the environment, which is the aim of integrated pest management (IPM). This protocol is clearly focused on obtaining healthy crops with low impact on agro-ecosystems as well as the promotion of biological pest control methods. The general principles of Integrated Pest Management establish that phytosanitary products are to be utilized in such a way that they do not increase the risk of development of resistances in harmful organisms, with the goal of maintaining the effectiveness of the products. Along these lines, according to integrated pest management, the sustainable use of phytosanitary products must also be reliable, consistent and long lasting. For this reason, it is essential that we possess an in-depth, scientific understanding of the phenomenon of pest resistance. Only in this way will it be possible to establish resistance management strategies that allow us to achieve effective integrated pest management.

Concept of pest resistance

Resistance arises when a pest population has genetically acquired the capacity to tolerate a dose of insecticide which would otherwise be lethal for the original insect population. Resistance must not be confused with a lack of product effectiveness. 'Poor results' may be due to a case of resistance, although it could also be an issue of incorrect product application, incorrect timing of treatment, incorrect choice of product, or a number of other reasons. Resistance is a quantitative biological phenomenon, meaning it can be graduated. The degree of resistance can vary between simply tolerating a stronger dose to virtual immunity to a product. The method for measuring the degree of acquired resistance is to compare the sensitivity of the study population (supposedly resistant) with the sensitivity of a susceptible reference population. In order to make this comparison we will use a concentration, or lethal dose, (LC50), which is the concentration or dose of insecticide that kills 50 % of the population. LC50 is used, and not

158

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

LC90 for example, because it allows us to estimate with the lowest margin of error. In addition, it makes it possible to conduct a bioassay and treat the population with a dose that kills above and below 50 % of the population. This will give us data for quantities higher and lower than LC50 to properly estimate the regression line. In contrast, with LC90 we would not have much data above this amount (more than 100 % cannot die), which is why the estimate error would be greater. The bioassay gives us an estimate of the degree of product toxicity on the population, that is, the degree of sensitivity or tolerance of the population. In order to estimate resistance it will be necessary to make a comparison with a reference population, while always using the same bioassay method. As a result, the resistance factor will be the division of the LC50 of the resistant population by the LC50 of the sensitive reference population. FR50

LC50 of the resistant population LC50 sensitive reference population

A resistance factor of (FR50) 2 will mean that in order to kill 50 % of the study population it will be necessary to double the dose that kills 50 % of the reference population. With a FR50 = 100, it would be necessary to multiply the dose by 100 in order to kill 50 % of the study population. It is important to mention that the presence of resistance in a sensitive reference population does not necessarily imply resistance in the field. For example, the reference population may have an LC50 = 0.5 ppm, and the study population an LC50 = 5 ppm. This would equate to a resistance factor of FR50 = 5 / 0.5 = 10. In other words, the study population is ten times more tolerant or resistant (or less sensitive) than the sensitive reference population. However, the concentrations tolerated may not exceed the application dose for the products in the field. Therefore, following this example, the field dose might be 500 ppm (of the active ingredient), meaning the study population, although 10 times more resistant than the reference population, would still be controlled in the field. There is indeed a natural variability between populations with respect to their susceptibility to insecticides, which must not be associated with the phenomenon of resistance. Prior to registering a product and launching it on the market, work is carried out to study its baseline susceptibility (or resistance). This is the degree of resistance that the populations possess before being exposed to product application. This work consists of collecting populations from various areas and at different times of the year, and conducting bioassays to obtain the LC50. It is quite common for there to be variability between the populations, and this natural variability is expected to be a factor of 10 - 20 (although higher factors have also been observed). Therefore, it is essential to know from the very beginning (before using the insecticide) both the baseline resistance (the LC50 combined with the populations) as well as the expected natural variability in the species. Thus, subsequent monitoring of variability in sensitivity (or resistance) in field populations, which have been treated with a compound, will consist of correctly interpreting data for LC50 that are obtained upon bioassaying the populations exposed to the product. This data (LC50 of field populations) can be compared with

159

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

the LC50 of the baseline, and it will be possible to determine whether there is a significant loss of sensitivity if the resistance factor obtained is considerably higher than the natural variability.

Development of resistant populations

Over the course of millions of years insects have had to deal with plant defenses, mainly the toxic substances produced by secondary metabolism. They have essentially been battling a wide range of toxins throughout their millions of years of evolution, which means they have developed highly efficient detoxification mechanisms. If we also take into consideration that many insecticides are an imitation of plant toxins (pyrethroids, neonicotinoids, etc.), we can understand that there is nothing new about the need for pests to develop resistances - they have be doing it for millions of years! The only difference now is that this process is somewhat faster; it is an adaptation process by populations to a changeable abiotic factor. The majority of pest species have a vast genetic background with respect to mechanisms for metabolizing toxins. The development of resistant populations simply selects the most appropriate mechanism. A population of insects or mites is composed of individuals with different degrees of sensitivity to a toxin (insecticide or mite killer). Thus, there will be some individuals that are very sensitive, some less sensitive, some more resistant, and others, although very rarely, that are resistant to the application dose of the pesticide.

Figure 1: variation within a population in terms of susceptibility or resistance to a composition Keys= Susceptibilidad: susceptibility - Resistencia: resistance - Dosis de campo: field dose

160

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

The resistance originates in the selection of these resistant individuals in a population through insecticide pressure. When the insecticide is applied, virtually only the resistant individuals survive, and some sensitive ones which the product did not reach; these will form the new pest population. If this process is consistently repeated, with the same product, the population will be made up exclusively of resistant individuals, meaning the application will cease to be effective. Basically, an evolution process occurs on a small scale and quite quickly. Selection pressure is the insecticide pressure (number and dose of applications) - the greater the pressure, the greater the effectiveness and speed of the selection. If the insecticide pressure is high, only the resistant individuals will have an opportunity to survive. Therefore, when the number of applications with the same product is greater, and/or the application dose is stronger, the possibilities of survival decrease for the sensitive individuals, selection pressure increases and resistance develops more rapidly. There are some species of pest that have a greater tendency to develop resistance. These pests are usually polyphagous, grow and reproduce quickly, have a large number of offspring, and possess low levels of mobility.

Polyphagous pests have more and better detoxification mechanisms since they are more adapted to having to detoxify substances from various plants. Moreover, they are exposed to insecticide pressure as they are present in more crops. The first factor makes it easier to select the resistance mechanism considering it already exists in the genetic background of the species, and the second increases insecticide pressure. Both factors combine to make these species those which normally show greater resistance problems (thrips, whiteflies, red spider mites, spodotera, etc.).

Since the phenomenon of resistance is an evolutionary selection process, if the rate of growth from egg to adult is faster and more generations and descendants are produced, the probabilities of selection will be higher. Thus, it will be easier to create a dominant resistant population from a very low number of resistant individuals in a population.

One of the factors that retards the development of resistance is crossing resistant individuals with sensitive ones. It is common for resistance to be a regressive trait, which means that the crossing of a resistant individual with a sensitive one will produce sensitive offspring. This type of crossing is more common when sensitive individuals can migrate to new crops easily. Therefore, if a pest is less mobile, by nature or it is impeded by a mesh, greenhouses, etc., or because a sensitive population does not exist (all crops are treated the same), a flow of sensitive individuals will not exist, and resistance will develop more quickly.

161

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

Resistance mechanisms

Resistance mechanisms to insecticides can be classified into four types:    

Behavioral Reduced penetration Metabolic Altered target-site

The behavioral mechanism consists of a change that enables the insect to not enter into contact with the pesticide. It is actually not a resistance but more of a pseudo-resistance, considering the pest dies if it is exposed to the pesticide. This type of resistance by means of evasion is not very common, and it does not cause serious problems in the field. In terms of the reduced penetration mechanism there are various factors that stop the toxin from reaching the target-site in sufficient quantity, resulting in an effective resistance. A thicker outer cuticle or one with different physicochemical properties, such as reduced lipophilicity, will reduce absorption of a contact insecticide into the bodies of the insects, allowing their survival. This mechanism does not usually provide high levels of resistance, but it multiplies the effects of metabolic resistance. Metabolic resistance is the most common of all the mechanisms, and it is the first to appear in the field. Living beings (insects, mites, all animals, plants, fungi, bacteria, etc.) possess a series of enzymatic systems that allow them to detoxify the potentially dangerous (toxic) products that enter their bodies. These enzymatic systems are the P450 monooxygenases (also called multi-function oxidases), esterases, and the glutathione S-transferases. These enzymes attack the pesticide and either isolate it and negate its toxic effect or metabolize it, which is normally the case with a more hydrophillic product, causing it to be excreted quickly. In relation to the sensitive individuals, the resistant ones have either a greater amount of these enzymes (quantitative improvement) or their enzymes are more effective in degrading insecticides (qualitative improvement). Metabolic resistance is normally gradual, progressively increasing the resistance factor through the accumulation of resistant genes (more and/or better enzymes).

162

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

Figure 2: Gradual increase in resistance when the metabolic mechanism is involved Keys= Susceptibilidad: susceptibility - Resistencia: resistance

In general, insecticides produce their toxic effect when they bind with a specific part of the metabolism, where they alter its normal function causing death. This binding point is called the target-site, and the way it alters the normal function is called the mode of action. Altered target-site resistance normally consists of a small change in the place where the toxin binds with the body. In this way, it ceases to be compatible and, therefore, ceases to have a toxic effect. Thus, a small genetic change (a mutation) in the gene that codifies for the protein that is the target-site, causes a small modification in its stereochemical disposition, impeding the pesticide molecule from binding. This type of resistance usually confers an abrupt, highlyelevated resistance factor to the pest since the insecticide ceases to act as a toxin, and the target species ceases to be susceptible. The probability of these mutations is extremely low, but if selection pressure is high (consecutive applications with the same product, excessive doses, overuse in a widespread area, high pest population, etc.) the selection process will continue to take place.

Figure 3: Abrupt increase in resistance when the altered target-site mechanism is involved Keys= Susceptibilidad: susceptibility - Resistencia: resistance

163

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

Three types of resistance can be identified: simple, multiple or cross. Simple resistance is when the resistant pest possesses various resistance mechanisms for different products. Cross resistance involves a single mechanism that confers resistance to different products. The development of resistance to a product by altering the target-site can confer resistance to other products that act the same way, at the same site (e.g., the development of resistance to a pyrethroid confers resistance to other pyrethroids). Metabolic resistance can confer cross resistance to other products with similar chemical structures, or similar chemical radicals, and not only in the same chemical group, but also among different chemical groups (e.g., the development of resistance to a pyrethroid can confer cross resistance to other compounds like carbamates). Cross resistance is a relatively common phenomenon when the metabolic resistance mechanism is involved.

Simple

Cross

Multiple

Figure 4: Types of resistance according to the resistance mechanisms present

Negative cross resistance also exists. It means that the more resistant an insect is to a product, the more sensitive another one will be. This phenomenon would be perfect for managing resistance in the field, but it is very uncommon.

A growing problem

Resistance to pesticides is currently a serious problem, not only in terms of insects and mites but also for fungi and weeds. Furthermore, this is not merely a problem with classic pesticides (organophosphates, carbamates, pyrethroids, neonicotinoids, etc.). It also occurs with the socalled biorationals, such as those which are regulators of insect growth (IGRs), Bacillus thuringiensis, and even in pheromones, among others.

164

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

The organisms that cause phytosanitary problems usually feature vast genetic flexibility, as it is precisely this characteristic that transformed them into pests. Therefore, almost any control method that is utilized exclusively will ultimately select the individuals capable of counteracting, by means of one mechanism or another, the effects of the method applied. Taking into consideration the wide-spread and lasting utilization of phytosanitary products, resistance to pesticides is quite common. However, other types of resistances and tolerances will also develop to other non-chemical control methods, such as biotechnical, genetic and even biological ones, if they are used exclusively and excessively. The key is to always use different control methods, combining them in a harmonious way, in order to optimize their effectiveness and sustainability. An integrated approach towards pest management will not only achieve sustainable use of phytosanitary products, as set out in Directive/2009/128/CE of the European Parliament and of the Council, but also the sustainable use of all pest control methods. New regulations on registration and labeling of phytosanitary products in the European Union are reducing the number of products available for crop protection. As there are fewer available tools, it is common to use them more frequently, which results in repeated use or overuse of certain compounds. It is this which brings about an increase in resistance development. In addition, the successful and growing implementation of biological control methods requires pesticides which are compatible with the natural enemies. As these compatible compounds are very scarce, it is common to use them repeatedly, which increases the risk of resistance development. Moreover, the lack of effectiveness of these products due to resistance development is even more serious (if that could be possible) considering that it could render the entire protocol of integrated control unfeasible. This could lead to its absolute abandonment and a return to a control system based on pesticides, rather than on biological control agents. On account of the existing risks mentioned in the paragraphs above, the development of antiresistance strategies is a key element to obtain an integrated pest management system that is reliable and consistent.

Resistance management strategies

Resistance management strategies are based on two fundamental premises:  

Resistance is easier to avoid than reverse. Selection pressure must be decreased.

The first premise is based on the fact that during the initial stages of resistance development the resistant individuals are very scarce and/or are less adapted than the sensitive ones. Due to this lower ecological valence, if selection pressure is decreased, the resistant individuals will

165

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

rapidly be displaced from the population. In contrast, if selection pressure is maintained, resistant individuals will begin crossing with the sensitive ones that are better adapted. This brings about reselections of individuals until resistant individuals are obtained, with high ecological valence and greater numbers. At this point it will be difficult to displace them from the population even if selection pressure is decreased. For these reasons it is absolutely vital to have a program that monitors resistance evolution and to develop techniques for early resistance diagnosis. In order for these to exist it will be necessary to first establish, as previously mentioned, the baseline susceptibility and expected natural variability, so as to obtain a point of reference. The second premise is based on the fact that when selection pressure is lower, selection intensity is lower and the rate of resistance development is as well. Everything that allows the sensitive individuals to survive, and the crossing of these with treated populations, will favor the preservation of sensitive populations, favoring the development of the resistance. Therefore, an adequate management of resistance consists of avoiding unnecessary treatments, applying products at the right time, maintaining periods without applications and without applications of a specific product, using correct doses, preserving shelters with sensitive individuals, rotating the use of active ingredients, reducing or reserving the use of some products, the use of synergies and all things associated with integrated control. Rotating the application of active ingredients consists of alternating between products with different resistance mechanisms. Considering the fact that different active ingredients, with either the same mode of action (same group) or different, may have cross resistances since they are affected by the same resistance mechanism, it is necessary to rotate said mechanisms. It is irrelevant whether the active ingredients are different; even if they are from different chemical groups, they must have different resistance mechanisms because it is vital for them not to have cross resistances. As a result, the survivors of an application will be sensitive to the following application and will not survive, and so on and so forth. This will lower the possibilities of resistant individuals establishing a population. In order to establish these anti-resistance strategies it is necessary to first study the resistance mechanisms involved, or that potentially could be, in the resistance to each compound. Another option for combining active ingredients is rather than alternating between them each time, they could be applied for periods of time. In this way, a crop can be treated with a specific type of product at specific growth stages, and at other times can be treated with another that does not feature cross resistances with the prior applications. These strategies are called "windows," and they exist during the course of crop life. During these "windows" different compounds are applied without cross resistances between "windows”. There is also the option of alternating in terms of space rather than time, which is known as a mosaic. This method consists of treating some areas with a product and others with a different one without cross resistance (different resistance mechanism). In the subsequent application, the product is changed in each area.

166

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Managing resistance to insecticides

One more alternative for rotating active ingredients is the mixing of products with different resistance mechanisms. If there is a very low frequency of resistant individuals for a product initially, this same type of frequency will be extraordinarily low with two products, that is, if they have different resistance mechanisms. Thus, the probabilities of resistance development will be reduced. However, this method is dangerous because if the frequencies are not very low due to prior use of the product, or cross resistances exist with other products that were used previously, this system will result in high selection pressure, and will therefore accelerate resistance development. Undoubtedly, the best anti-resistance strategy is a true integrated pest management system, in which different control methods are combined effectively. A multiple control strategy approach is what will make it possible to achieve a reliable and lasting pest control system. Furthermore, to achieve sustainable use of phytosanitary products, it will be necessary to follow resistance management strategies based on:      

Determining baseline susceptibility and natural variability Understanding existing, and potential resistance mechanisms involved Recognizing cross resistances and possible synergisms Establishing rotation and optimum use (dose, times, etc.) of pesticides Incorporating all of this into an integrated management system of all the pests in a crop Monitoring resistance development and updating strategies

167

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

Greenhouse pest and disease control: Sublimators Corpus Pérez Martínez Cajamar Research Centre ‘Las Palmerillas’

Introduction Sulphur sublimators are mainly used to prevent the onset of fungal diseases such as powdery mildew in a greenhouse. This technique is effective and compatible with integrated and organic farming. Powdery mildew is a major fungal disease that attacks vegetable crops, both open field and in greenhouses. The wind or air currents favor the spread of spores, which germinate on leaf surfaces, colonizing mycelium within the leaf and producing yellow patches or powdery white on top and white down on the undersides. With the advancement of the patch, the tissue becomes necrotic and leaves dry out to the point of causing severe defoliation. The optimum conditions for powdery mildew to develop are temperatures of 26 ⁰C and relative humidity of 70 % (Cádenas, 2003). Sulphur is one of the most commonly used products in intensive agriculture, and has been for decades, especially for its fungal and acaricidal properties as it prevents the occurrence of powdery mildew and delays the appearance of spider and broad mites. Traditionally sulphur has been applied by dusting (powdered sulfur) in spray form (liquid or wettable sulfur), or sublimated (solid sulfur), the least used by growers in Almeria. Sublimators using sulphur to prevent the occurrence of mildew is very widespread in the world, mainly used in pepper crops and floriculture (Huertas & Rodriguez, 2001). Cajamar Research Centre ‘Las Palmerillas’ has been working on the use of sublimators to control powdery mildew in greenhouses since 2007.

168

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

Figure 1: sublimator for powdery mildew control in a greenhouse

The sublimator consists of a cylindrical vessel with an electrical resistance and a vaporization bowl into which the solid sulphur is placed. The heater melts the sulphur which gradually evaporates as a gas. The gaseous sulphur penetrates the powdery mildew cells as a result of its solubility in the lipids of the cell walls of the fungus (Garcia-Jimenez, 1997). Once inside the cell the sulphur is reduced to hydrogen sulfide and interferes in various metabolic processes by blocking cell respiration and inhibiting the synthesis of nucleic acids and proteins. These processes occur for eight hours following treatment, with maximum activity occurring around the third hour.

Photo 2: changes of state during the sublimation process

Temperature control is a very important factor to prevent the generation undesirable sulphur oxides (SO2, SO4, etc.). It should not exceed 155 ⁰C. (Figure 3)

169

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

 261 ⁰C :VERY DANGEROUS OXIDES FREED  250 ⁰C :BROWN/GREEN  232 ⁰C – 261 ⁰C: SELF INFLAMMATORY  188 ⁰C: BOILING POINT  159 ⁰C: INCREASED VISCOSITY RED/BROWN  145 – 155 ⁰C: IDEAL VAPORISATION TEMPERATURE  119 ⁰C: FUSION  SOLID

Figure 3: the working temperatures of a sublimator

The power consumption depends on the sublimator model, ranging between 75 and 100 watts from initial start up to the ideal vaporization temperature. Thereafter to maintain that temperature power consumption is 50 watts. Using sublimators it is necessary to consider a series of basic recommendations:   

The greenhouse must have an electrical installation. Install a sublimator for every 200 - 300 m2 and distribute them staggered to cover the entire surface to be protected Use sulphur cylinders of more than 99.0 % purity or 98.5 % micronized sulphur although it contains a higher proportion of impurities

Figure 4: sulphur cylinders used in sublimation

170

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators    

  

Place sublimators 30 cm above the crop and raise them as crop grows Do not overfill sublimator bowl as it could overflow upon melting Monitor operation and periodically remove any waste Operation always takes place at night, so timers are required in the greenhouse. Start by operating for 3 hours at the beginning of the crop (small plants) and progressively increase to 8-10 hours, depending on the density of sublimators, climatic conditions, the type of greenhouse, crop sensitivity, etc. The amount of sulfur sublimated depends upon sublimation temperature Disconnect sublimators 1 - 2 hours before entering the greenhouse and ventilate early in the morning Place a shield over each sublimator that prevents sulfur concentrate being sublimated onto the plastic cover and to facilitate the dispersion of the product

Figure 5: protector which avoids the accumulation of sulphur on the plastic covers

The use of sublimators on horticultural crops has more advantages than disadvantages. Amongst the advantages are: The use of sublimators is a very efficient technique which prevents the appearance of powdery mildew on horticultural crops. The incidence of powdery mildew in different horticultural crops following application of powdered sulfur, either on leaves or sublimated, has been evaluated at the Cajamar Research Centre ‘Las Palmerillas’. In peppers, the most effective method for controlling this fungal disease was sublimated sulfur (8 hours maximum operating time) powdery mildew was detected on only 15 % of plants compared to 45 % of plants by applying foliar sulphur or 100 % of the plants with no preventive-curative treatment (Pérez, 2013). By reducing the number of hours of sublimated sulphur (4 hours at most) powdery mildew was detected on 95 % of plants, so it was not a very effective method (Chart 1). For tomatoes, the results were very similar to those obtained for peppers.

171

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

Plantas con oídio (%)

120

AS(Dosis baja): 1,5h AS (Dosis alta): 3 h

AS(D. Baja): 3 h AS (D. alta): 5 h

AS (Dosis baja): 5 h AS (dosis alta): 8 h

100 80 60 40

20 0 0

100 Días desde el trasplante

Azufre foliar

150

200

Azufre sublimado (Dosis alta)

Azufre sublimado (Dosis baja) Chart 1: percentage of plants with powdery mildew in peppers when applying foliar sulphur, sublimated sulphur low dose (maximum operating time 4 hours a day) and high dose sublimated sulphur (maximum operating time 8 hours a day). Azufre foliar = Foliar sulphur Azufre Sublimado = Sublimated sulphur - Dosis baja = Low dose - Dosis alta = High dose - Plants con oidio = Plants with powdery mildew - Días desde el transplante = Days since transplant

The use of sublimators is a technique that reduces fungal infections from the start of the crop, reducing the need for specific treatment for this disease, as well as reducing the number of hours devoted to such a task. The use of sublimators is a technique which is compatible with integrated pest management because it is beneficial insect friendly. The Cajamar Research Centre ‘Las Palmerillas’ has evaluated the effect of sublimators on natural enemies, mainly Orius laevigatus, Amblyseius swirskii and Nesidiocoris tenuis. The Accumulated Daily Incidence (ADI) was calculated according to the work of Moreno-Vazquez (1994), Hair & Benitez (1994). The sublimated sulphur did not affect the implementation of biological control as populations of Orius laevigatus and Nesidiocoris tenuis were similar to those observed when applying foliar sulfur, while the population of Amblyseius swirskii increased by 27 % compared to foliar sulphur application (Chart 2).

172

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

IDA A. Swirskii en planta

Greenhouse pest and disease control: Sublimators 350 300 250 200 150 100 50 0

(a 0

100

120

140

160

180

Días después del trasplante

IDA Orius laviegatus en planta

Azufre foliar

Azufre sublimado

160 140 120 100 80 60 40 20 00

(b) 0

100

120

140

160

180

Días después del trasplante Azufre foliar

IDA Nesidiocoris tenuis en planta

Azufre sublimado

500 400 300 200 100

0 0

100

150

Días después del trasplante Azufre foliar

Azufre sublimado

Chart 2: evolution of Amblyseius swirskii (a) and Orius laevigatus (b) and Nesidiocoris tenuis (c) populations with different methods of sulphur application. Días después del transplante = Days following transplanting

173

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators The use of sublimators favours crop development (Photo 6) and appearance especially leaves and fruit, because there are no sulphur deposits from phytosanitary applications (Photo 7).

Figure 6: appearance of different crops with and without sublimated sulphur

174

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

Figure 7: appearance of leaves and fruit with foliar and sublimated sulphur applications

A very important aspect to be considered when using sublimators is the greenhouse cover. The sulphur and chlorine, derived from the use of phytosanitary products, are the main causes of plastic degradation, clearly reducing the life of greenhouse covers. For this reason, in 2012, the Spanish Committee of Plastics for Agriculture (CEPLA) adopted a guideline which fixed the maximum permitted concentration of sulphur and chlorine in the plastic covers to ensure its longevity. It also recommended that the dose of phytosanitary products used be proportional to the time, such that the maximum yearly accumulated concentration does not exceed 1.000 ppm sulphur and 70 ppm chlorine (Table 1). Plastic

Sulphur (parts per million)

Chlorine (ppm)

2 Seasons

1.500

100

3 Seasons

2.000

150

3 Years

3.000

200

Table 1: Maximum accumulation limits (CEPLA Directive 2012)

175

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

When sublimators are used without any type of protection, the highest concentration of sulphur is occurs in the area immediately surrounding the sublimator, therefore after 11 months exposure and 1.591 hours sublimating sulphur, accumulated sulphur concentration is greater than 3.000 parts per million (Chart 3). This is more than the maximum permitted for a three year old plastic cover, as well as the recommended 1.000 ppm per year maximum, according the CEPLA guideline. The direct consequence of exceeding these maximum concentrations is that the plastic will break (Photo 8).

3500

Concentración azufre (ppm)

3000 2500 2000 1500 1000 500 0 6 MESES (789 horas)

7 MESES (981 horas)

11 MESES (1591 horas)

Chart 3: Sulphur concentration (ppm) in the plastic cover over the unprotected sublimator KEY: Concentración de azufre = Sulphur concentration - Meses = Months - Horas = Hours

Photo 8: breakages in the plastic cover due to unprotected sublimator use

176

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators The use of a protected sublimator reduces the sulfur concentration in the plastic cover by 46 %, preventing premature degradation of polymers (Chart 4).

Concentración de azufre (ppm)

1000 800 600 400 200 0 SIN PROTECTOR

PROTECTOR

Chart 4: sulphur concentration (ppm) accumulated in the plastic cover over a protected and an unprotected sublimator working for 447 hours Keys: Sin protector: Unprotected - Protector: Protected

Photo 9: protected sublimator in a melon crop

177

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Greenhouse pest and disease control: Sublimators

References Cabello, T; Benítez, E. 1994. Frankliniella occidentalis (Thysanoptera; Thripidae). En Moreno, R (Ed.). Sanidad vegetal en la horticultura protegida. Consejería de Agricultura y Pesca. Junta de Andalucía. Sevilla: 157-178. Cádenas, F, Gónzález J y Hernández, M. 2003. El cultivo protegido del tomate. En ‘Técnicas de producción en cultivos protegidos’. pp: 483-537. Ed. Caja Rural Intermediterránea, Cajamar. CEPLA 2013. Directriz CEPLA para filmes de cubierta de invernadero. Folleto. www.cepla.com García-Jiménez, J. 1997. Enfermedades del melón causadas por hongos y nematodos. En ‘Melones. Compendios de Horticultura 10’: pp: 131-139. Ed. Namesny. Ediciones de Horticultura SL. Barcelona Huertas, J. y Rodriguez, J. Optimization of sulphur sublimators used in the Colombian flower industry. Symposium on Thermodynamics and the Design, and Improvement of Energy Systems. International Mechanical Engineering Congress and Exposition. New York, USA.Noviembre 2001. Moreno-Vázquez , R., 1994. Análisis de datos. En: Moreno, R(Ed.). Sanidad vegetal en la horticultura protegida. Consejería de Agricultura y Pesca. Junta de Andalucía. Sevilla: 109-112. Pérez, C y Gázquez JC, 2013. Uso de sublimadores para el control del oídio en hortícolas. Vida Rural 360: 40-43

178

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

Biological control in greenhouses Mónica González Fernández Cajamar Research Centre ‘Las Palmerillas’

Introduction

As with all human activities, agriculture has an impact on the natural environment, in this way man modifies his environment to adapt it to his needs. However, these changes necessarily entail alterations in the balance of relations between the different elements that shape and make up the eco-system. Inevitably, agricultural activity destabilises the balance fostering a significant simplification of the natural environment, which increases as production intensifies with the aim of increasing productivity. In this sense, agricultural development has meant the loss of bio-diversity, and one of the main consequences is the vulnerability of crops to pest infestation and disease. The concept of pest infestation is totally anthropocentric, inasmuch as it implies harm to humans. In agriculture, the notion of pest infestation is generally associated with terrestrial arthropods, insects and mites that feed on the material of the “phytophagous” plants resulting in economic harm. However, one should exclude micro-organisms; virus and bacteria, also fungus and mould, since the damage they cause are commonly called diseases. In general, one can apply the term “pest infestation” to any animal form that, as a consequence of a rupture in the ecological balance, reduces the production or the quality of foodstuffs in such a way that justifies intervention against it. In the natural world there are no pest infestations, in a natural, balanced eco-system there is no demise of a plant population because of attack by any phytophagous pest. As previously stated, in a natural eco-system, ecological balance is established where the insects that feed off the plants serve as prey to their natural enemies and as such never develop into great populations. In the case of intensive protected agriculture it is obvious that the humid conditions and temperatures, along with the abundance of food in the interior, provide an excellent, stable atmosphere for the development of these pest infestations. This is aggravated by the lack of the natural enemies that assist in the control of the phytophagous insects within the interior of the greenhouses, for these reasons, the pests develop with ease and to a greater degree within the greenhouses than out of them. Pest and disease control is one of the greatest challenges that a farmer faces. Traditionally pest control in agriculture has been based, with growing frequency, on the use of chemical compounds, even reaching the point of weekly preventive

179

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

applications. This usage abuse, even exclusively, of plant protection of our crops has lead, paradoxically, to a greater incidence of infestations and diseases. This occurs because the products also affect the natural enemies of the pests which are also more susceptible, resulting in their elimination from the environment. The use of phytosanitary products has created resistance to the insecticides in the pest populations, as well as the appearance of environmental problems and toxicology problems both for the farmer and the consumer. It should also be taken into consideration that the use of these products also increases cultivation costs as the active ingredients tend to be very expensive, as do the equipment and the labour necessary for treatment application. Chemical control, and associated resistance to the same, means that the farmer must use higher and higher doses of the phytosanitary products to continue to combat the infestations and has to use a greater amount of active ingredients, leading to an unsustainable situation. These problems have lead to the search for viable alternatives to the traditional chemical control of pest infestations in the field of Integrated Production. Integrated production advocates the production of high quality foodstuffs using methods that respect the health of the consumer and of its producer using environmentally friendly production processes, minimising and justifying the use of agrochemical products whilst ensuring the economic viability in a way tailored to suit the production methods of the actual agricultural companies. Integrated production makes the maximum use of natural production resources and mechanisms and ensures long term commitment to sustainable agriculture, introducing biological and chemical means of control and other technology that is compatible with, amongst others, the demands of society, the protection of the environment and agricultural productivity. With Integrated production systems use Integrated Pest Management. This is defined as a system in which all of the available methods are combined to reduce the damage caused by the infestations, with the least impact on the environment. Within this framework, special mention has to be made of the recent new Royal Decree 1311/2012 of the 14th of September, which comes into force from 1st of January 2014, and which responds to the European Directive 2009/128/CE establishing the framework of communal performance to attain a sustainable use of phytosanitary products through the reduction of risks and the effects of use of the phytosanitary products on human health and the environment, promotion of integrated pest management and of alternative approaches or techniques, such as non-chemical methods. Amongst the methods being contemplated in the Integrated Pest Management, the most interesting is Biological Control, which according to the IOBC (the International

180

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

Organisation of Biological Control) is defined as the use of living organisms, of their natural resources or their products, to prevent or reduce the losses or damage caused by pest organisms.

Biological pest control

Biological control forms part of a wider phenomenon, the natural control mentioned previously. Natural control involves the action of all the environmental factors, both physical and biological, that govern the densities of populations of different organisms and is defined as “the maintenance of the density of a more or less fluctuating population, of an organism within certain limits (higher and lower) definable within a period of time, thanks to the actions of abiotic and/or biotic environmental factors” (De Bach, 1985). On the other hand, biological control is defined as “the action of parasites, predators and pathogens on the maintenance of the densities of populations of other organisms at levels inferior to those that exist in their absence”. In other words, biological control is a natural phenomenon of the regulation of the density of plants and animals by natural enemies. In this sense it can be considered that the natural enemies are the most important natural control agents and those that exert the greatest effect on the pest infestation populations. What makes natural enemies even more interesting is that they can be manipulated by man. Where natural biological control is carried out by the natural enemies of the pests present in nature, applied biological control is that which is carried out by biologically controlled organisms (BCOs), also known as beneficial insects, which are bred and released by man. The use of biological pest control has its advantages and disadvantages. Amongst the advantages it should be noted that the problems of the infestation are not seen to be intensified, nor are new problems created. The natural enemies have the capacity to seek and find the infestation as well as increase in number and to spread, all of which allows some reduction in control costs. One of the most important aspects is that the use of natural enemies does not generate resistance within the infestations and as such the control is long-lasting. Biological control has no risk of toxicity either for the plants or for people, does not contaminate the environment, does not leave waste, therefore it is un-necessary to comply with safety periods. Consequently it is possible to obtain a higher added value in production compared with other agricultural production and fulfil the requirements of both the market and the consumer with respect to increased food safety. Biological control also entails some disadvantages, such as, for example, the length of time that the action takes and that the infestations are never completely eradicated.

181

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

As living things they are unpredictable and can occasionally be difficult or expensive to obtain or to implement. Furthermore, there are no biological products on the market that effectively control all of the phytophagous pests that affect our crops. It must be noted that the great incidence of pest infestations and diseases in our crops, for the number of species as much as for the increased populations, requires the use of different natural enemies, in addition to its use together with chemical combat, always using authorised natural products that are compatible with the auxiliaries. Also, on many occasions, the efficiency of control depends on climate conditions. In this sense, the microclimate conditions within the greenhouses sometimes hamper the activity of the natural enemies of the pests. Biological control requires technical knowledge for the release of the natural enemies and continuous monitoring.

Biological control agents

In order to carry out biological pest control in a determined agricultural ecosystem and to select the most suitable BCO to introduce, it is necessary to classify the infestations present as real or induced. The real infestations are those that have almost no effective natural enemies whereas the induced do but are incapable of acting for some reason. Amongst the introduction strategies, the introducing of exotic species could be considered for establishment in the ecosystem; or conversely one could opt for the conservation or improving the effectiveness of the native or indigenous natural enemies. There is also the possibility of artificially increasing or augmenting the presence of the BCOs naturally present in the ecosystem. The biological control of the real pests requires the introduction of exotic BCO. In the case of induced infestations the conservation of the native beneficials should be tried and if that is not sufficient they should be introduced. Historically, classic biological control has consisted of the introduction of natural pest enemies. It should also be taken into account that many of the pests that affect our crops are exotic or introduced and as such, on many occasions, efficient natural enemies have been sought in their original area. For classic biological control to be successful it is not only necessary to find an effective natural enemy but that it also adapts well to the conditions of the environment where it is to be introduced. It has to be borne in mind that the introduced organisms will be competing with the native natural enemies. On the other hand, augmentative biological control entails the introduction of natural enemies, imported or otherwise, and the manipulation of the environment to favour the increase of their populations. This strategy involves, therefore, the rapid increase of the population levels of the natural enemies; given that in their own time they

182

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

would take too long to do so or never reach the levels necessary to control the pest species. This type of biological control requires that the most efficient natural enemy be identified, selected and mass-produced and this depends on the financial cost. It is necessary to ensure that the creation of this organism is of a constantly high level and allows for release en masse within a short time of being selected, bearing in mind, of course, the genetic deterioration and the loss of efficiency that results from controlled laboratory conditions; and lastly their release into the countryside. The BCO’s can be classified as entomophagous (predators and parasites) and entomopathogens (virus, bacteria, fungi, nematodes and protozoa). Predators are insects or mites that feed off other animals that they consider prey. They are characterised by their consumption of numerous prey whilst in an immature state and until they complete their development in adult form. Except when in egg state, the predator acts freely, the eggs being deposited on or near to the prey, in such a way as to allow that once the nymphs and larvae emerge they are able to capture and kill their prey to feed themselves. They tend not to be specific. The principal groups are: neuropterans, coccinellids, mirids, anthocorids, mites, phytoseiids, etc. Parasites are insects that live and develop in, or on, another arthropod, their host, causing its death in a short period of time. Unlike the predators, parasites tend to be quite specific in their selection of a host. The majority are hymenopterans and dipteral. Finally, the entomopathogens are micro-organisms, bacteria, virus, fungi, protozoa and nematodes capable of causing diseases in insects. Nowadays there are numerous commercial preparations based on these pathogens that are used for the control of many pest infestations.

4 The main pest infestations found in crops grown under plastic in SE Spain and their natural enemies The number of species of arthropods and pathogens that cause losses in protected horticulture is very high. The greatest economic impact is caused by approximately 61 species. Bearing in mind that the total area is divided into eight main crops, this implies a significant number of pest infestations. In the region of 42 % of these species are arthropods, followed by fungi at 27 %, virus 19 %, bacteria 11 % and the rest are nematodes. Amongst the most problematical arthropods are the order of Hemiptera, the sub-order of Homoptera, which encompasses whitefly (Aleyrodidae family), aphids (Aphididae family) and mealybugs (Pseudococcidae family), amongst others. Other orders included in the families of greatest impact on protected agriculture are Thysanoptera, represented by thrips (Thripidae family); the Diptera order, which contains the Agromyzidae family of leafminers and the Lepidoptera order which covers butterflies and moths. In addition, within the Arachnid classification we find the

183

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

Acariform order which encompasses several families of mite pest such as Tetranychidae (spider mite), Tarsonemidae (broad mite) or Eriophydae (Aculops lycopersici - tomato russet mite). A brief description of the main pest infestations and their natural enemies will be given as follows.

a. The Hemiptera order a.1 Sub-order Hemoptera a.1.1 Aleyrodidae Family Whitefly

Although all species of whitefly are phytophagous, of the one thousand five hundred known, only two are a serious problem in protected greenhouse horticulture. These are Bemisia tabaci and Trialeurodes vaporariorum. They are not only important for the direct damage that they do to crops but also as vectors for viral diseases such as tomato yellow leaf curl virus (TYLCV) or cucumber vein yellowing virus (CVYV). Both adults and nymphs introduce the sucking mouth parts into the plant tissue and suck out its juices. As they are incapable of digesting the high sugar content of the sap it is excreted in the form of drops of molasses on the surface of the leaf or fruit. This molasses is the perfect substrate for fungus (Cladosporium spp.) to form on leaves and fruit, reducing the photosynthetic capacity of the plant, its transpiration and depreciating the fruit. In ornamental crops it reduces the aesthetic value of the plant. Several beneficial species have been commercialised for the biological control of whitefly amongst which can be found as many parasitoids as predators. The biological control protocols for whitefly in the majority of the crops are based on the use of the predator mite Amblyseius swirskii and of the parasitoid Eretmocerus mundus if dealing with B.tabaci; or Encarsia Formosa in the case of T. Vaporariorum. In those crops where predatory mites are not well established then bugs from the Mirid family such as Nesidiocoris tenuis or Macrolophus caliginosus, whose use is controversial because of their omnivorous feeding habits, which with high-density population and scarcity of prey, can cause damage to plants.

a.1.2 Aphididae Family Aphids

Aphids belong to a very extensive group that contains many species that damage cultivated plants. They are normally polyphagous species with a wide range of host plants. Among the most frequent species in horticultural crops are the green peach aphid Myzus persicae and the cotton aphid Aphis gossypi, although the larger aphids

184

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

such as the green potato aphid Macrosiphun euphorbiae and Aulacorthum solani are also important. Aphids tend to appear during the warmest times of the year, in the form of focal points, and disperse very quickly which is why early detection is fundamental. As homipteras, like the whitefly, the damage caused to the plants is very similar. They also transmit viruses such as the cucumber mosaic virus (CMV) or the zucchini yellow mosaic virus (ZYMV). Aphids have a great number of natural enemies; parasitoids and predators as well as entomopathogenic organisms. All of the parasitoids that are used in greenhouse biological aphid control belong to the Aphidiiae family particularly Aphidius colemani and to a lesser degree Lysiphlebus testaceipes. For the largest species of aphids Aphidius ervi is used. Furthermore, aphids are the prey of numerous predators belonging to different orders; Diptera, Neuroptera, Coleptera. In the Diptera order the aphids can be predated by the larvae of diverse species of the Syrphidae family (hoverfly) and also from the Cecidomydae family (gall midges). Similarly, the larvae of many neuropteros (Chrysopidae Family) are very active devourers of aphids. Within the coleoptera group the Coccinellidos family encompasses many genera that feed on aphids, Harmonia, Adalia, Coccinella, Scymnus etc. In their case, it is not only the larvae that feed on the aphids but also the adults.

b. Thysanoptera order b.1 Thripidae Family Thrips

There are many species of thrips that may appear related to protected crops, but the reality is that they are only a few that cause the vast majority of damage. Generally speaking there are two species; Frankiniella occidentalis and Thrips tabaci, the latter being only slightly problematic. The flower thrips, F. Occidentalis, is very polyphagous, it feeds mainly by piercing the cells of the plant tissue; however it can also act as a predator of the eggs of the spider mite. The way it feeds causes direct damage that can depreciate the commercial value of the fruits. However, the greatest danger is in the transmission of tomato spotted wilt virus (TSWV) to peppers and tomatoes. The control of this pest infestation is based on the placement of chromatic traps that allow early detection and mass trapping, and the introduction of beneficial predators. Predators of various species belonging to different groups are commercially available.

185

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

On the one hand there are the predatory mites of the genus Amblyseus and on the other, different bugs (heteroptera) of the Anthocoridae and Miridae families are used. Both groups of predators, mites and bugs, have the advantage of being able to feed off pollen and as such are able to sustain themselves and reproduce independently without the presence of live prey in the crop, thus allowing the maintenance and growth of their population throughout the crop cycle. With regard to the predatory mites, the most commonly used in the greenhouses is A. swirskii, which efficiently devours the small thrips larvae. It is a very mobile mite that seeks its prey on both flowers and leaves. When not feeding on adults, thrips control is complemented by the release of predatory bugs such as Orius laevigatus (Anthocoridae) or Nesidiocoris tenuis (Miridae), according to the crop being treated.

c. Diptera order c.1 Agromyzidae Family Leaf miners

Within the Agromyzidae family, the genus Liriomyza encompasses 23 species that damage different crops, and of these, only 5 species, considered very polyphagous, cause damage of any serious economic importance. In the case of protected horticultural crops, there are mainly two, L. Trifoli and L. Bryoniae. The damage caused by the adults when feeding and laying eggs as well as the tunnels produced by the larvae when feeding, cause significant damage to the plants and their photosynthetic capacity is considerably reduced in severe cases of infestation. The tunnels vary in form according to the species and the type of host plant, although they tend to be elongated and winding in relation to the vascular tissue of the leaf. Biological control of the miners is primarily carried out with parasitoids because of their effectiveness. Although there are a number of parasitoids that are capable of controlling this pest and that appear spontaneously within the greenhouse, it is Digilyhus isaea (Eulophidae family) that is used commercially. This is a small wasp-like insect whose adult form feeds on the molasses it finds on the crop. Digilyhus takes control of the miner by introducing its eggs in the tunnel next to the miner larvae which will serve as food during its development. Although to a lesser degree, within the greenhouse there are other efficient predators for the control of the miners. The mirid Nesidiocoris tenuis feeds off the larvae, whilst the diptera known as the hunter fly (Coenosia attenuata), that appears spontaneously, feeds off the adults.

186

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

d. Lepidoptera order d.1 Noctuidae family Numerous species of butterflies and moths cause different types of damage to protected crops grown under plastic, the majority belonging to the Noctuidae family. These are nocturnal butterflies that, in their larval state, cause serious economic losses by their consumption of the crop. They generally feed off the leaves, shoots and fruit by cutting pieces of the plant with very well developed mandibles. Amongst the species of the lepidoptera pests, the most important are the Spodoptera exigua and the Helicoverpa armigera. Other species that cause damage are Chrysodeixis chalcites and Autographa gamma. Among the biological control agents for noctuid infestation, predators, parasitoids and entopathogenic organisms can be found, which although they are neither predators nor parasitoids, they do exert sufficient control. Many heteroptera predators belonging to different families (Orius laevigatus, Nesidiocoris tenuis, Nabis pseudoferus) like neuropteras (Chrysoperla carnea) contribute to the control by their consumption of eggs and small caterpillars. Furthermore, there are several species of parasitoids that appear spontaneously in the greenhouses and help to control the caterpillars Cotesia sp, Hyposoter didymator and Chelonus oculator amongst others. Commercially, species of the genus Trichogramma have also been used discreetly. Nowadays, different entomopathogenic organisms are being commercialised. On one side are the various formulations based on Bacillus thuringiensis, bacteria that cause death through disease, and on the other, preparations of the Nuclear Polyhedrosis Virus are also being commercialised.

d.2 Gelechidiiae Family Tuta absoluta

Special mention is made of this microlepidoptera because it is a very important pest infestation in tomato crops. Tuta absoluta was found for the first time in Spain in 2007 and experienced an extremely rapid expansion which turned it into one of the most significant infestations of this crop and it can also affect other solanaceas such as the aubergine. The main damage is caused on the leaves and the young shoots, although the un-ripe fruit can also be affected via the stalk. The tunnels formed by the Tuta larvae are very different to those of Liriomyza sp. On the leaves, the caterpillars consume all of the mesophyll respecting only the foliar epidermis. The tunnels that are produced by this way of feeding are wide and of indifferent bundles that end up necrotising.

187

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

In Spain, N. tenuis is a good predator of Tuta; however for optimum biological control it is also necessary to optimise the strategies to establish this bug very rapidly. Currently, the releases in nurseries are providing very successful results in this sense. There are also some parasitoids that are capable of parasitizing the Tuta eggs, as in the case of Trichogamma sp although its commercial use is not very extensive.

e. Arachnida class e.1 Subclass acari(na) e.1.1 Acariform order e.1.1.1 Tetranychidae Family Spider Mite

The mites of the genus Tetranychus are known as spider mites and make up one of the most significant pest infestations in Spanish horticultural crops. The four main species are: T. Urticae, T. turkestani, T. ludeni, and T. evansi. These mites possess a pair of chelicerae that they use to feed on the surface material of the plants. When the cell juices are suctioned out, the yellow patches and deformities that are caused reduce the photosynthesising capacity of the leaf. When the colonies are very large webs, formed by the silk threads, cover some parts of the plants entirely. For the control of the spider mite, predators are most commonly used, amongst which are phytoseiid mites such as Phytoseiulus persimilis, which is the most commonly used, although Amblyseius californicus and the gall-midge Feltiella acarisuga are also to be found but these last two are not included in the release programme in the greenhouses.

e.1.1.2 Tarsonemidae Family Broad mite

The broad mite, Polyphagotarsonemus latus is a polyphagous mite that generally attacks the young organs of the plant, usually on the underside of the leaves. The edge of the leaves become rigid and deformed as a result of its feeding activity. Peppers are the most affected but it can also appear on cucumber, aubergine and watermelon. Biological control of broad mites can be carried out using phytoseiid predatory mites like Amblyseus swirskii, A. californicus and A. cucumeris that exert good control and can be introduced into the crop as a form of prevention.

188

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

Biological control management in the greenhouse

Implementing a biological control programme in the greenhouse requires greater knowledge on the part of the grower than that of the more traditional pest control methods. For the study of the variables that affect the incidence of infestations and diseases, it is necessary to consider the greenhouse as a system made up of the crop, the populations of the different pests that affect it and the beneficial fauna linked to it. And to take into account that the balance of said eco-system is affected by the interaction of different factors such as the configuration of the enclosure that defines it (hermticity and characteristics of materials), the equipment installed (heating, refrigeration, CO2) or the management of said system. In short, the technology used in the greenhouse and its management affects in some way, each and every one of the living components of the greenhouse: plants, pests and beneficial fauna and they determine the intensity of the phytosanitary problem areas or the success in their resolution for each greenhouse. The evaluation of the interaction of the abovementioned factors with the behaviour of the pest populations and of the beneficial fauna should supply useful information to ensure the success of the incorporation of biological combat in pest control. The success or failure of biological control is going to depend on many factors such as the rhythm of release, the timing and the most suitable areas for those releases and which phytosanitary products are compatible with these beneficials. In order to determine the right time to carry out these releases close monitoring is needed. It is also necessary to know the life-cycle of these beneficial organisms to be able to determine the frequency of release and to maintain their populations for as long as possible. The crop is a primordial element in every strategy of pest control. The phytosanitary state is going to depend on the cultural practices which they are subject to (irrigation, fertilising, de-leafing and pruning etc.) and in turn will have a decisive influence on the management of the beneficial fauna released into the greenhouse. To do this, it is necessary to synchronise the cultural measures (pruning, de-leafing...) with the releases of the beneficial fauna into the greenhouse so as to prevent these tasks interfering with the process of establishing the natural enemies. So, the pruning should always be carried out, where possible, before each release of natural enemies and should not be repeated during the following two weeks. The efficiency of biological pest control is closely inter-related with the characteristics of the greenhouse, with its equipment and with the management provided, the teams, the crops, the beneficial biological agents. A better knowledge of all of these relationships results in greater efficiency and effectiveness of integrated pest and disease control in the horticultural crops of the greenhouse. Further necessary investigative efforts must

189

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

be made in the future to optimise and consolidate this important technological advance.

6 Development of a strategy for biological control through conservation within the framework of southeastern Spain’s intensive horticulture In view of the importance that biological control has achieved in the areas of competitiveness and image towards foreign markets for the agricultural and food-production sector, the implementation of biological pest control is essential for the protection of the ongoing sustainable development of intensive horticulture. In this context, a strong commitment to create a new line of research dedicated to biological control through conservation has been settled upon. The idea is to contribute to the development of more sustainable agriculture from the agro-ecological perspective, until now, an unexplored procedure for this kind of very intensive agriculture. In this way, the biological control through “conservation’ emerges as an essential factor for the sustainable development of intensive horticultural crops. In the area of open-field agriculture it has been proved that biological control can benefit from adequate habitat management. The presence of natural enemies can be increased if food resources are supplied by the surrounding vegetation. It is a fact that biological pest control is affected negatively by the isolation and loss of semi-natural habitats, a circumstance that lowers biodiversity in agricultural landscapes. This happens in every agricultural area, where the same species prevails for hectares upon hectares, whether it is orange trees, loquat trees, persimmon trees, cotton plants, broccoli plants or greenhouses. The important role that hedgerows, windbreaks or nearby forests play in agricultural areas is well known, given that they increase the presence of natural enemies. Biological control through conservation can be applied to the Spanish Mediterranean basin, making use of native plants, which are totally adjusted to our climate and soil. In those highly altered agricultural areas, of which the western part of Almeria is the prime example, the native perennial plants provide, besides nectar and pollen, a shelter and a moderate microclimate which contribute to the improvement of the natural enemies’ performance. The potential for pest control through auxiliary fauna is, therefore, necessary related to our ability to exert some kind of control over the habitat close to the production areas. As a result, our main objective is the selection of native plant species which will be used afterwards through Xeriscaping techniques, with the aim of improving the landscape, increasing biodiversity and decreasing the impact of infestations in the areas where intensive horticulture is concentrated, without the need of extensive monitoring by growers. These actions are expected to have a beneficial effect on the population dynamics of pests’ natural enemies, thus reducing their impact on the crops. At the end of 2010, a forest-island was set up in Cajamar Research Centre ‘Las Palmerillas’. It contains approximately 900 plants belonging to 29 different species, which in turn belong to 18 botanical families, selected according to a multi-criteria analysis that today is subject to research studies. The most important criteria considered for the selection of plants were those

190

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Biological control in greenhouses

related to specific resources that plants provide to the different beneficial insects (food, shelter or breeding sites). The differences in plant architecture were also considered, as well as their habit, availability in forest nurseries and degree of protection, ease of handling, as well as whether these plants are considered as possible virus reservoirs. In such a forest-island, plants are arranged in the same way they would be spontaneously in nature so that they look like a spot of natural vegetation. Once the plants have grown to a suitable size, a sampling of the arthropodofauna associated with these plant species is carried out, and has been monthly since May 2012. The samples obtained are processed in the laboratory, with the aim of identifying the arthropods present in each plant, establishing their population dynamics during the year and understanding their role in the ecosystem. Similarly, each of the species’ flowering is being monitored once a week in order to know which floral resources are available at any given moment. This will allow us to know the resources that make these plants attractive to these insects (flowering period, flower morphology, the presence of extrafloral nectaries, etc.) In conclusion, this experimental plot will be useful to describe the dynamics of beneficial arthropods associated with these species and will allow us to decide which of them are most suitable to be used in landscape restoration. In the future we will be able to design these ecological infrastructures adapting to the space availability between greenhouses. It is expected that these actions will have a beneficial effect on the population dynamics of pests’ natural enemies, reducing in this way their negative impact on the crops. The aim here is to design personalized hedgerows.

References Conocer y reconocer- Las plagas de los cultivos protegidos y sus enemigos naturales. 1992. Koppert B.V. 288 pp. Organismos para el control biológico de plagas en cultivos de la provincia de Almeria. 2006. Colección Agricultura. CAJAMAR Caja Rural. 231 pp. Organismos para el control de patógenos en los cultivos protegidos. Prácticas culturales para una agricultura sostenible. 2010. Colección Agricultura. Fundación Cajamar. 528 pp. Control biológico en invernaderos hortícolas. 2009. COEXPHAL. 178 pp. Jan van der Blom. 2010 Applied entomology in Spanish greenhouse horticulture. Proc. Neth. Entomol. Soc. Meet. Volume 21:9-17. Perspectivas del control biológico en agricultura bajo plástico. 2010. Cuaderno de Estudios Agroalimentarios 01. Fundación Cajamar. 122 pp.

191

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management

Best agricultural practices in the greenhouse: the key to success in integrated pest control management Juan Carlos Gázquez Garrido Cajamar Research Centre ‘Las Palmerillas’

Introduction

In recent years it has become evident that there is growing concern about the consumption of better quality produce and the effect that phytosanitary products have on the environment. In response to the demand for safe, quality food products a change of strategy towards biological control is called for. The integration of crop-protection methods and of environmental protection has given rise to an increase in the use of cultivation techniques that try to minimise the use of synthetic chemical substances in favour of other phytosanitary products that are more respectful of people’s health. Biological control that seeks to control crop enemies by the use of live organisms that feed off or destroy them is highlighted amongst these methods. The integrated management of pest infestations involves the combined use of all available control methods, taking into account the level of parasite population, the beneficial insects and environmental impact. There are four key points for success in a programme of integrated pest management in the greenhouse: prevention, follow-up monitoring, good usage of natural enemies and by the rational use of chemicals in a way that is compatible with the natural enemies.

Prevention - cultural measures

A thorough overhaul of the whole growing system must be undertaken, including the structure of the greenhouse and crop management, to facilitate the action and the reproduction of the beneficial fauna that has to be applied and observed. In order to carry out biological control, it becomes necessary to apply a series of cultural measures such as: 

Checking for tears in the plastic

192

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management  

    

Use of anti-insect mesh of 10 x 20 threads cm2 in the side walls as well as the roof vents The mulching of the ground: covering the earth with a layer of plastic (black, transparent or other type) to avoid direct contact between the plant and the fruits with the moisture in the soil. In this way the emergence of diseases can be controlled. With the use of black plastic weed growth can also be controlled Entrance areas and double doors Sulphur dusting The use of healthy, pest free plants with their corresponding phytosanitary passport The removal of weeds and vegetable waste Initiate cleaning up of waste materials. To do this, treatments with residual products in previous crops should be avoided

The placing of chromotropic traps: these traps are devices designed to attract and capture insects and are made up of a coloured plastic sheet coated with a layer of an adhesive substance. The insects are attracted by the colour and become stuck to the trap. Types:  

Yellow: Made from sheets of yellow plastic. The insects (especially aphids and miners) are attracted to this colour and become stuck to the trap Blue: The same design as the above but are coloured blue which is especially attractive to thrips

Figure 1: shows the double gate arrangement and the placement of chromotropic traps inside it

Figure 2: shows a disinfection mat

When one crop is planted soon after another, the passing of infestations from the previous one to the next must be avoided. Infestations such as thrips (Flankliniella occidentalis) and the miners (Liriomyza spp.) complete part of their cycle in the soil and therefore continue to emerge for several weeks following the elimination of the previous crop. During the

193

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management changeover periods between crops, the blue chromatic sticky traps have proved to be very effective against thrips, in the same way as the yellow traps are against whitefly and miners.

Photograph 3. Shows chromotropic traps placed between crops

Photograph 4. Shows a blue chromotropic pad with a pheromone for thrips

Crop monitoring

For the study of the internal variables that affect the incidence of pest infestations, the greenhouse should be considered an ecosystem that comprises: the plant, the populations of the different phytoparasites that affect it and the beneficial insects linked to it. However, there is a series of factors arising from the ecosystem itself which affect the balance. These can affect the seriousness and intensity of a phytosanitary problem at any given time, and in any given crop. The rational control of pest infestations and diseases, both within integrated control programmes and in their use per se, relies on a decision-making process. This process comprises a number of tools: sampling techniques, intervention thresholds, control methods and their implementation. Knowledge of the populations of the pest infestations and their natural enemies and diseases is imperative to be able to carry out pest control procedures in any crop. For good monitoring to take place, the first step is to speak to the grower; he is the one who best knows the track record of the plot, (the location and progress of the pest infestations). Therefore, the degree of involvement of the producer is one of the determining factors in exercising adequate control over pest infestations and diseases. Then the plot must be visited to quantify the levels of pest infestation, diseases and natural enemies.

194

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management We should have a simple but efficient record sheet of infestation count that allows fast but exhaustive tracking to detect possible focal points of broad mites, red spider-mites, aphids or russet mites. An easy sampling technique is based on the percentage of pest presence and of the natural enemies. It consists of counting 25 flowers and 25 leaves and noting the presence or absence of thrips and Orius on the flowers and whitefly and Amblyseius swirskii on the leaves. There are some very useful products for the sampling and capture of pests, especially within the Integrated Pest Management (IPM) and Integrated Crop Management (ICM) programmes, for example, chromotropic sheets that allow the detection of the influx of pest species from outside or the increase of the population within the greenhouse. Chromotropic sheets are an essential tool for keeping track of the evolution of the infestations in greenhouses or plots of any crop and to thus be better able to decide the right moment for phytosanitary intervention and/or the release of beneficial organisms. The sticky traps are used at the rate of 5 - 10 per 1.000 m², being mainly placed below sidewall vents, and generally where the risk of insect invasion is greatest. There are chromotropic traps (sampling) specially designed to carry out sampling in that they come supplied with a protective sheet divided into 5 strips that can be removed separately. The chromotropic traps that are used for sampling are placed at a ratio of 2 - 3 sheets of each colour per cultivation site or greenhouse, in the areas of greatest risk of pest entry. Every week, or at the most opportune frequency, one of the bands of paper attached to the sheet should be removed in order to periodically observe the catch. Furthermore, the placing of blue or yellow sheets or gummed rolls in sufficient densities at the start of a crop, is a very important complement (physical barrier) to phytosanitary treatments and beneficial organisms, also contributing to the reduction of incidence of virus transmission by insects in susceptible crops. The recommended placement of the gummed capture rolls is along the sides of the greenhouses, at side vent height and also underneath the roof vents.

Figure 5: view of mass - capture chromotropic traps

Figure 6: chromotropic sample traps

195

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management The use of pheromone traps to detect the first flight of noctuids is also an essential element. They represent a fundamental tool in deciding the most opportune time and the most suitable phytosanitary product to use; combining the use of the sex pheromone with adhesive traps or with insecticide bait, insects of a certain species can be captured. Sex pheromones are chemical substances produced by insects (mainly females) to attract individuals of the same species (males) for mating. The chemical signal produced is sensed by the male through his antennae. They are used as a method of combat and for monitoring. There are two possible control methods: a) to achieve sexual confusion, a mass of pheromones is released to confuse the males at the time when they are searching for a mate; b) to carry out a mass capture: a sufficient number of pheromone traps are placed in order to reduce the number of males, thus reducing the global fertility of the population and the intensity of the attack by reducing the total number of individuals. Monitoring consists of the placing of 1, 2 or 3 traps with pheromones and so detect the start of sexual activity in the males; these traps may be of the delta type with a gummed sheet or a funnel trap with water or an insecticide tablet (deltamethrin and lambdacyhalothrin). There are different types of pheromone traps on the market, depending on the size of the species to be captured; a) Delta traps: for small-sized moths and b) Funnel trap - Flycatcher: which can be used for the capture of larger sized moths (Spodoptera, Heliothis,....) as well as dipteras (Dacus oleae, Ceratitis capitata,...). Pheromones are mainly used to detect flight and to follow the evolution of moths and flies in greenhouses and open-air plots. They are a fundamental tool to decide the best time and the most suitable phytosanitary product, combining the use of the sex pheromone with adhesive traps or with insecticide bait, the capture of insects of a particular species is achieved. The insects captured are quantified and the evolution of the adult population of the insects is obtained (capture curve). The evolution of the capture should be linked to the detection of the different evolutionary stages of the insect within the crop. 

Number of traps recommended: ∙



Minimum distance between traps: ∙ ∙



For monitoring: 3 - 5 traps per pheromone per site

Same species traps: Different species traps:

Pheromone duration:

50 metres 100 metres 6 weeks

196

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management

Figure 7: Delta pheromone traps for the capture of Lepidoptera

Figure 8: Funnel trap - Flycatcher pheromone trap for the capture of Lepidoptera

However, to trap nocturnal Lepidoptera moths en masse, those which really work without having to distinguish between sexes or species are the ultraviolet light traps, which are also highly recommended for the control of Tuta absoluta. It is important to take the precaution of placing them outside the greenhouse so that they do not serve as an attraction. Another option is to place them inside, but they should be well protected so as to prevent this effect. There is a commercially available sex pheromone of Frankliniella occidentalis which contains a synthetic version of the sex aggregation pheromone of this pest. The natural pheromone is produced by the males of F. occidentalis and attracts both males and females to mate. It can be used in any crop which is sensitive to Frankliniella occidentalis for early detection of infestation or to improve the sensitivity of the monitoring sheets for thrips, particularly in conditions of low- level infestation or in crops that are susceptible to thrips damage. They should be hung some 30 - 50 cm above the crop. They should be placed in staggered positions leaving 8 - 10 metres between each one. Similarly, a distance of some 5 metres from the sides should also be left. Each emitter is directly attached to the centre of a blue capture pad; for correct monitoring use 100 pheromones traps ha-1. The duration of the pheromone, once it is in place, is between 4 and 6 weeks depending on the environmental conditions.

197

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management

Figure 9: ultra-violet light trap

Figure 10: detail of the capture of adult Lepidoptera in an ultra-violet light trap

Once the sampling has been carried out, decisions have to be made, to evaluate the level of damage, analyse possible evolution and if the economic threshold is exceeded, to decide if any treatment is to take place or not, what cultural practices can be of help if releases are carried out, how they are to be done and what dose.

Good crop and natural enemy management

In all integrated pest management (IPM or ICM) programmes all the compatible techniques need to be integrated with each other to allow the level of pest infestations to be reduced: cultural measures, treatments with compatible products, release of natural enemies, crop operations, etc. Climate control must be improved with the aim of eliminating extremes of temperature and relative humidity. Factors that now greatly restrict the adaptation and reproduction capacity of many species of natural enemies. The crop is an essential element in every pest control strategy. The phytosanitary state of a crop will depend on the cultural practices which it undergoes (irrigation, fertilisation, pruning, etc). The programming of cultural measures (pruning etc.) has to be synchronised with the releases of beneficial insects to prevent these from interfering with the establishment process of the natural enemies. Many species, above all predatory mites and bugs, depend on the pollen that flowers produce for their reproduction. Therefore, we must ensure that the flowering of a pepper crop remains stable throughout the entire crop cycle, which may involve a change in plant pruning, changes in fertiliser to produce plants with more leaves and also in the way of harvesting, more staggered, this is achieved by picking unripe fruits at times.

198

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management

A biological control programme: recommendations

In integrated pest management programmes, all available methods of pest control, biological included, are used. Preventative and physical methods are particularly important.

5.1

Prior to planting

There are many procedures that must be carried out before a crop is planted which will enable the reduction and control of pathogen action. Featuring amongst these measures:         



        

Soil preparation tasks such as levelling and sub-soil preparation in case of problems with water-logging, scarifying, Rotovator, etc. The use of suitable manure, well rotted and of identifiable origin Grafting onto resistant rootstock Removal of vegetable waste before the new crop Disinfection of tools and packaging such as trays, crates etc. In the case of soilless crops or in nurseries, the use of substrates with sanitary guarantees When necessary, disinfection of the soil by solarisation for 40 days Maintain a pre-planting period of at least 15 days Meet all mandatory requirements and those recommended in the October 10th 2007 Order in which both compulsory and recommended measures are established for the control of viral diseases in horticultural crops Use plantlets from authorised nurseries and ensure that the Phytosanitary Passport of the horticultural plantlets acquired is kept for a year. Pay special attention to the monitor and register the treatments in the nursery. (Except in the case of direct sowing) Check the greenhouse condition, covering any tears in the plastic with anti-insect mesh (10 x 20 cmˉ¹) and install a double gate Arrange the structure of the greenhouse to provide optimum climate control Installation of irrigation systems appropriate to the needs of the plot that will facilitate operation and maintenance In the case of reservoirs, keep them covered to stop pathogen transmission via irrigation water No dusting of chemical products ( excepting sulphur) Remove weeds from both inside and outside the greenhouse through the use of contact herbicide or by pulling them up Place a disinfection mat at the entrance to the greenhouse Pressure-clean the mesh to eliminate accumulation of soil, red-spider mite and broad mite Carry out sulphur dusting (20 - 40 kg ha-1) of soil and structure

199

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management  



Use granular products in the soil for the control of ants, beetles, crickets etc. with specific products like Clorpyrifos (10 kg ha-1) Place chromotropic capture traps and insect detectors around the interior perimeter of the greenhouse and, if there has been a previous crop, covering the whole surface, 50 yellow sheets and 50 blue sheets per hectare then water thoroughly. Yellow adhesive rolls may also be used along the sidewalls and gates Thorough cleansing of treatment equipment. Fixed treatment system should be cleaned with bleach, soap and wetting agent, as should the rubber stops and pipes to be used. Any excess liquid should be disposed of away from the greenhouse. The tank and hoses must also be cleaned well. In the case that there are crops with chemical and biological control on the same plot, it would be advisable to use separate set of equipment for each At times, it may be worth transferring the natural enemies from one crop to the next

5.2 During cultivation Amongst the cultural measures to be carried out during cultivation the following should be emphasised:    



   

The removal of weeds that could compete with the crop The removal and/or shredding of vegetable waste from pruning, de-leafing etc. that can cause infection or infestation Irrigate correctly. The frequency and the amount will depend on the type of soil, climate, crop etc. and especially to avoid problems of overirrigation or flooding A balanced supply of fertiliser, avoiding excess or lack of any element that may cause the appearance of disease or infestations. For example, an excess of a nitrogenous fertiliser will increase the plant’s susceptibility to pathogen attack Pruning, de-leafing, and cutting back to allow adequate formation and balance of the plant organs, facilitating pathogen control. Whilst improving the ventilation and facilitating the penetration of pesticides during phytosanitary treatments, avoid leaving cuts Removal of pest and disease, especially seriously, affected organs and plants. If not, they will become sources of infection The maintenance of a healthy crop during the entire season so as to avoid it becoming a reservoir for pathogens Frequent disinfection of the tools used throughout the whole crop cycle (shears, utility knives, etc.), thus eliminating the possibility of future contagions Adequate greenhouse management so that optimum conditions for the development of certain pathogens do not occur

200

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management

5.3 From planting to the start of the releases Take into account the chemical products and the safety period for the release of beneficial insects. Do not use active residual matter like pyrethrin, malathion, imidacloprid, cypermethrin, procymidone, etc., so do not use any product that exceeds the 2 - 3 week safety period. Carry out a multi-residue analysis 2 weeks before the first release, for the avoidance of doubt regarding the existence of any residues that could affect natural enemies. Placement of yellow and blue adhesive chromotropic monitoring sheets. If it is foreseen that the natural enemies might become stuck to the yellow or blue chromotropic sheets when released into the crop, the sheets should be removed. Carry out weekly sampling to be able to estimate the presence of pest infestation. Use coloured marker clips to advice of the presence of infestation inside the greenhouse, very useful to locate the pockets of spider-mites and aphids.

Figure 11: sampling of infestation and diseases

Figure 12: the marking out of a pocket of red spider mite

5.4 Rational chemical control For the introduction of beneficial fauna to take place, the pest and disease pressure must be taken into account, also the phytosanitary treatments carried out to guarantee the absence of residues and finally, the phenological state of the crop and the cultural practices followed. Once the first introduction of beneficial insects has been made, only products that are COMPATIBLE with the beneficials may be used. Beneficials should always released late in the afternoon.

201

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management Should the use of phytosanitary treatment become necessary, consult the secondary effects on the natural enemies. In preference, try to treat only the pockets, using the most appropriate method to increase the effectiveness and thus reducing the number. Use the best method for application of the treatment, so as to increase effectiveness at the same time as reducing the number. Close the ventilators when treating the greenhouses or adjoining crops to avoid the drifting of the chemical products into the biological control greenhouse. It is important to retain relatively high humidity (>60 %) because this favours the establishment of the beneficials

Rational chemical control compatible with biological control

Pesticides are chemical substances that are used to combat the causative agents of infestations and diseases in crops, with the aim of achieving greater quantity and quality production. Nowadays, there are a great number of specific pesticides on the market, for each group of harmful agents, insects, bacteria, mites, etc,. These products come in all states, shapes and sizes (solids, liquids and gases) and the way they are applied in the field is also very varied. Furthermore, the behaviour on the crop on which they are used, the way in which they act on parasites, their toxicity to people, animals or to the crop itself, and the residues produced, vary a lot according to the type of pesticide that is applied. It is very important that the people who work with the pesticides have proper knowledge of the product and its characteristics, so that their handling and management will be correct. All of this also contributes to there being no negative effects on the environment, neither for the people who apply the pesticides nor for those who consume products that are treated with this type of substance. The application of phytosanitary treatments in a rational way requires the adoption of a series of measures, amongst which feature: 

 

Verification of the need to carry out the application: the pathogen must be correctly identified, as must the level of the population, the vegetative state of the crop and the presence of secondary or beneficial fauna The selection of product to apply: it is important to bear in mind the active ingredient, the way it acts, the way it penetrates the plant and the alternating of active substances Application techniques: the correct functioning of treatment equipment should be checked, produce a suitable mix of pesticides, take opportune security and personal

202

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management protection measures, and take into account the climactic conditions at the time of application (wind, rain, etc.) If pockets of broad mite, spider mite or aphids are detected, the risk that they pose must be calculated and, where appropriate, localised treatment is recommended. On occasion, it is also advisable to carry out a generalised treatment of compatible products so as to reduce the pest pressure. In either case, the effectiveness of the treatments to be carried out must be maximised: choose the most suitable time of day and select the right product and the best suited application method. The concept of the efficiency of chemical control may be established as optimising the application of pesticide within the crop from a technical and economical point of view, with the correct dosage reaching the pest population or pathogen, and causing a toxic effect on them, whilst avoiding the loss of active ingredients into the environment, as well as avoiding harm to people and natural enemies. The applied pesticide can cause the reduction or elimination of natural enemies. The importance of the harmful effects of the pesticides on the beneficial insects of the crops led to the creation of a Workgroup of the International Organisation of Biological Control (IOBC). The damage that phytosanitary products can cause to the natural enemies are classified as: a) Direct effects:  

Lethal effect: mortality within a short space of time < 24 hrs or the non-hatching of eggs and pupae Sub-lethal effects: reduction in fertility, and alteration of search behaviour

b) Indirect effects:  

The ingestion of contaminated host food Reduction of the host prey

We can define compatibility as the property of a phytosanitary product to control a specific pest or disease without eliminating the natural enemies. Nowadays, there are lists detailing secondary effects of pesticides on auxiliary fauna (natural enemies and bumblebees) that are put together by the companies who produce and supply the natural enemies, but it would be more beneficial if these effects were harmonised by the appropriate administration. According to the IOBC the secondary effects of the pesticides on beneficial organisms are divided into 4 categories. The residual (persistent) effect is expressed in the number of weeks and indicates the length of time that the pesticide remains harmful to the natural enemies.

203

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Best agricultural practices in the greenhouse: the key to success in integrated pest control management Symbol or Category

Reduction in capacity of control

Inoffensive

< 25 %

Slightly harmful

25 - 50 %

Moderately harmful

50 - 75 %

Very harmful

> 75 %

Effect unknown Residual effect or Persistency

The number of weeks that the pesticide is harmful to natural enemies.

Source: http://www.koppert.nl/Efectos_Secundarios.html

204

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Diseases affecting the main horticultural crops in the greenhouses of Almeria María Antonia Elorrieta Jove Department of Phytopathology, LABCOLOR, Almeria

Introduction

Plant diseases are considered to be the harmful alterations caused in plants by microscopic organisms such as virus, bacteria, fungi and nematodes, among others. These diseases can attack at any time during a plant's life cycle, and even after harvest. For this reason it is important to monitor the health status of crops in relation to these pathogens until the produce can be marketed. The fact that a disease appears in a crop is the result of several factors that coincide simultaneously:   

The presence of the pathogen agent responsible for the disease The presence of a susceptible host, which in this case is the crop The presence of adequate climate conditions that allow the disease to act

It is obvious that the presence of the pathogen is the first requisite for the disease to act. It must also be a virulent strain and possess sufficient inoculum density to generate the disease, and it is necessary, of course, that the pathogen and host come into contact. The host must be susceptible to the pathogen, meaning it cannot be a resistant variety, and it must be in a stage of physiological development sensitive to said pathogen. If the infection arises during an early stage of plant development, the effects of pathogens are normally more severe than during an adult stage. Finally, climate conditions prove to be the definitive factor in many cases that allow the disease to act. For example, fungi and bacteria usually require very specific temperature and moisture conditions, but these vary depending on the organism. There are numerous bacterial, fungal and viral diseases that can be considered as relevant in the horticultural crops in the southwest part of the Almeria province. There are even more so if those caused by weak pathogens are included - ones which act in unfavorable conditions for plant growth. Based on this context, this article will attempt to offer a brief outline of only those diseases that are frequently present in the most common crops in the province, mainly focusing on cucurbits and solanaceae. Information will also be provided on diseases which, although are not present in the study area, can be important due to their epidemiological implications and/or their particular significance in regard to plant health legislation.

205

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Relevant bacteria in the horticultural crops of Almeria

In general, the most common bacteria responsible for the development of diseases in vegetables (and all plants) belong to a few taxonomic groups such as the genera Pseudomonas, Xanthomonas, Clavibacter, Curtobacterium, or the species Ralstonia solanacearum and Acidovorax avenae (both previously included in the genus Pseudomonas). The aforementioned bacteria can be classified into three main groups according to the way they function: airborne, pith and vascular.

2.1 Airborne bacteria This group includes mainly the bacteria that act on plant surface and belong to the genera Pseudomonas, Xanthomonas and Acidovorax avenae subsp. citrulli. 2.1.1 Pathogenic plant species belonging to the genus Pseudomonas The genus Pseudomonas includes a ubiquitous group of Gram-negative bacilli, which includes numerous species of varying importance. Forming part of this group are saprophytes, which are relevant because of their high metabolic versatility. However, it also includes pathogenic human, animal and plant species. As for phytopathogenic species, the most notable in the area of study would be Pseudomonas syringae. This species produces a fluorescent pigment under UV light in King B medium and includes numerous pathovars. One of them is polyphagous (Pseudomonas syringae pv. syringae) while others are highly specific in terms of the crop that they can infect (P.s. pv. tomato in tomato; P.s. pv. lachrymans in cucurbitaceae; P.s. pv. phaseolicola in green beans, etc.). The various P. syringae pathovars attack a variety of crops and produce leaf specks, which can also affect the stem and fruit. In general, this entire bacteria group requires moderate temperatures, around 20 ⁰C, and, above all, very high humidity. They are transmitted through the seed and remain in vegetable waste and wild hosts for a long time, and, like epiphytic microbiota, they also remain on the surface of numerous plants. 2.1.1.1

Pseudomonas syringae pv. tomato

Is responsible for leaf spot disease in tomatoes, which is known in the Almeria area as the "tomato black speck bacteria”. It affects all parts of the plant and its most common symptom is the appearance of small brownish to black leaf spots, frequently surrounded by a yellowish halo (Figure 1). These spots can later extend to stems and petioles. These symptoms are observed in the Almeria area, particularly in nurseries and some leaves in culture media. However, the most characteristic symptom associated with greenhouse farming in the area is long blackened stretches of plant stem (Figure 2) with the occasional presence of blisters or vesicles full of bacteria. This blackening advances along the petioles of the leaflets and fruit branches (Figure 3) and continues up to the points where leaves and fruit begin. What appears on the fruit itself is described as small brownish spots, something not commonly found in

206

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria Almeria. The bacteria can infect the seeds and later manifest itself in seedlings if climate conditions are adequate.

Figure 1

Figure 2

207

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 3

2.1.1.2

Pseudomonas syringae pv. lachrymans,

Which is responsible for angular leaf spot on cucurbits, is found in all crops grown in Almeria (cucumber, melon, watermelon and courgette) and produces spots on mainly leaves, stems and fruit. It is most commonly observed in cucumbers, on whose leaves these bacteria initially produce small round or irregular yellow spots. As they grow and coalesce they acquire an angular appearance since they are bound by the leaf vein structure (Figure 4). The spots can dry out and turn brownish-grey until the affected tissues flake off. In relatively high humidity conditions they can form drops of an exudate that resemble teardrops. Stems and fruit can be affected in the same way, and in fruit it can cause a systemic infection able to contaminate seeds, which is one of the forms of disease transmission. In other cucurbits such as courgette and melon, symptoms similar to those in cucumbers can appear, and, in the case of melon, even cankers have been observed on stems as well. As for courgette, dark spots surrounded by a yellowish halo that are approximately 2 mm in diameter (Figure 5) have recently been appearing on leaves quite frequently in the study area. It is also possible to observe alternations in leave development due to damage that took place during plant growth. These alterations include the appearance of holes, deformations and "cracks" in the leaf and stem, which can easily be mistaken for other pathogens.

208

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 4

2.1.1.3

Figure 5

Pseudomonas syringae pv. syringae

Affects different hosts, among which are tomatoes. It produces symptoms similar to those of P. s. pv.tomato, although it lacks the epidemiological consequences of the latter. As for melons in Almeria, this pathogen has been observed to be associated with brownish, necrotic areas on leaves. Other species of Pseudomonas identified as phytopathogens, at least in crops such as cabbage, lettuce, onion, endive, chicory, etc., are Pseudomonas marginalis pv. marginalis, P. viridiflava and P. cichorii. All three can cause leaf wilting similar in lettuce, but the most aggressive in this crop would be P. cichorii. The latter causes black vein in lettuce and considered transmissible through seeds and capable of also producing a systematic vascular infection that is difficult to control. Pseudomonas corrugata belongs to this genus but is addressed in the section dedicated to pith diseases. 2.1.2 Plant species belonging to the genus Xanthomonas The genus Xanthomonas belongs, like Pseudomonas, to the Family Pseudomonadaceae. Similarly, it is also formed by aerobic Gram-negative bacilli capable of forming pigments called xanthomonadins, which are responsible for the typically yellow colonies that these bacteria produce. The genus includes different phytopathogenic species, although the most important in horticultural crops is the species Xanthomonas campestris. The latter, like Pseudomonas syringae, includes different pathovars such as X. campestris pv. campestris (polyphagous, extremely relevant in the genus Brassica), X. campestris pv. vesicatoria (solanaceae), and X. c. cucurbitae (cucurbits). This type of bacteria is usually involved in the development of leaf damage in its various hosts as well.

209

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 2.1.2.1

Xanthomonas campestris pv. vesicatoria

Mainly affects tomato and pepper crops. In tomato plants it produces the characteristic bacterial leaf spots similar to, but larger than those of P. syringae pv. tomato. They are dark circular spots measuring several millimeters that become angular as they grow and feature a very faint yellow halo. The centre portion of these spots can eventually detach. Long dark blotches can appear on stems and petioles, the same way small blacks spots can initially appear on fruit. As they grow they acquire the appearance of pustules surrounded by an oily halo that is several millimeters in diameter. In pepper plants it produces spots that also look like pustules that reached up to 5 mm in diameter in leaves stems and fruit. This seed-borne bacteria is very common in tropical areas since it grows well in warm climates (20 - 35 ⁰C) with high humidity. In Almeria this bacteria is uncommon, or inexistent for that matter, most likely because the area does not offer the climate conditions necessary for its development. Nevertheless, considering these bacteria are seed-borne, their introduction into a farming area by means of a poorly-controlled seedling batch implies a threat that must be monitored. 2.1.2.2

Xanthomonas campestris pv.cucurbitae

Mainly affects pumpkin crops and appears on leaves in the form of spots similar to, but smaller in size than those produced by P. s. lachrymans. This is not found in any of the crops typically grown in the Almeria area, but it is also uncommon in Europe, where it has been known to affect cucumber plants. This pathogen harms mainly the fruit of pumpkin plants, in which it causes rotting during storage. It is also quite relevant for the fact that it is transmitted through seeds. 2.1.2.3

Acidovorax avenae subsp. citrulli

Acidovorax avenae (previously referred to as Pseudomonas avenae and, therefore, featuring characteristics typical of the genus Pseudomonas) includes the subspecies Acidovorax avenae subsp. citrulli, identified as a pathogen of cucurbits, on which it causes "bacterial fruit blotch”. This is not found in the Almeria area, or the rest of Spain for that matter, but it is widespread in the U.S.A. and South America. Its seed-borne transmission and capacity to act on seedlings makes it extremely relevant with regards to nurseries. The characteristic symptoms observed during seedling transplants are moist, oily areas on the underside of the cotyledons, or first leaves, often running parallel to veins, and the presence of a yellow halo (Figure 6). The infected areas elongate and become angular and eventually blacken and necrotize. Some seedlings will wither and die immediately after infection whereas others can retain the bacterial infection and do not exhibit symptoms until fruit begins to grow. Stems, petioles and roots are not infected and do not show symptoms. The infection can spread from infected leaves to the fruit, where a dark green blotch appears on the upper surface and rapidly expands with favorable environmental conditions until it covers the entire surface. This infection cycle usually begins with contaminated seeds, which find an excellent medium for propagation in nurseries as they offer high temperatures and humidity and favor dispersion of the pathogen to other plants via droplets from sprinkler irrigation. It is also worth mentioning

210

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria that the transplant of infected seedlings to the field can cause serious consequences. This bacteria can be included with harmful organisms that are not present in Spain and, therefore, it is vital to maintain extreme vigilance.

Figure 6

2.2 Pith necrosis bacteria The main bacteria that are included in this group are those that target the interior of the plant exclusively, such as Pseudomonas corrugata. In addition, the group includes those that penetrate and disintegrate tissues down to the plant pith, attacking via plant lesions or damage at the superficial level. Said process corresponds to the bacteria Pectobacterium carotovotum subsp. carotovorum, which could have been included in the previous group as well. 2.2.1 Pectobacterium carotovorum subsp. carotovorum Pectobacterium carotovorum subsp. carotovorum, formerly Erwinia carotovora subsp. carotovora, is a bacteria that causes watery rot, accompanied by a foul odor, in various crops such as peppers, tomatoes, aubergines, courgettes, cucumbers, melons, watermelons and lettuce. It appears in tissues in the form of water-soaked lesions that grow quickly and soften

211

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria tissues, without causing chlorosis. Eventually, the bacteria break down infected tissues, whether they are soft such as leaves and fruit (Figure 7) or hard tissues like stem. This rotting is accompanied by the release of a watery exudate, somewhat more visible in fruit, which is loaded with bacteria and is a vehicle for the dispersion of the pathogen. In the case of tomato crops, it is mainly observed affecting stem pith, where it decays the interior part of the plant. The bacteria then advances outward, where it ultimately kills the entire stem and wilts all parts of the plant above the original lesion. The problem is similar in pepper and aubergine, although the disease mainly affects fruit on pepper plants, above all during postharvest (Figure 8), but it is visible in the field and on the stem. Courgettes are one of the most widely affected crops in the Almeria area. Damage caused by the bacteria appears mainly at stem level, at nodes, considering they represent good access points for bacteria to enter tissue and they usually exhibit high levels of moisture, vital for bacteria development. As for cucumber, the disease mainly affects the basal part of the stem, most likely due to higher moisture content in this area, leading to complete decay of tissue and, as a result, wilting and plant death, just as in the case of courgette.

Figure 7

Figure 8

Transmission of this bacteria is mainly airborne. It is spread either by the handling of plants (probably the principal cause of bacteria dispersion for a crop) or by contact between plants, or contact with water or watery exudate that is secreted from rotting tissues. This bacteria is ubiquitous meaning it can be assumed that numerous sources of infection and bacterial reservoirs exist. The climate conditions that allow this type of rotting to take place feature high levels of humidity and warm temperatures; ideally around 24 ⁰C or slightly higher, and the required presence of available water in plant tissues so that infection may occur.

212

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 2.2.2 Pseudomonas corrugata This is another bacteria that can be found in tomato crops, albeit less frequently. It affects plant pith (Figure 9) causing necrosis that does not lead to external tissue disintegration, nor is it accompanied by a foul odor, as occurs in the previous case. Its presence may not have any other greater consequence than only that. Moreover, on many occasions the plant continues to grow without showing symptoms that are more serious; nevertheless, plants may be weakened and feature irregular fruit ripening.

Figure 9

Transmission can also take place as a result of plant handling, mainly during pruning. Once transmitted its development is favoured by excessively nitrogen rich fertilization.

2.3 Vascular bacteria This group would include mainly bacteria that colonize the vascular system of plants, which corresponds to species from the genera Clavibacter and Curtobacterium and the species Ralstonia solanacearum.

213

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 2.3.1 Pathogenic plant species belonging to the genus Clavibacter Clavibacter includes species of great phytopathogenic importance and consists of Grampositive bacteria, which are pleomorphic. Various species comprise this genus, but in terms of typical horticultural crops that which is most relevant in the Almeria area would be Clavibacter michiganensis subsp. michiganensis. It causes bacterial canker of tomato, which is its main host, and the only crop in this case that concerns Almeria. This bacteria is a vascular pathogen that produces cankers and leaf spots but whose main effect, caused by a systematic plant infection, is the drying and wilting of the plant. The latter effect can be combated to varying degrees but features marginal to interveinal chlorosis that gives the plant a burnt appearance (Figure 10). These symptoms are accompanied by vascular necrosis, the browning of vessels (Figure 11) and the formation of hollow cavities in the pith. It is also possible for small grey or black spots to appear on leaves, stems and fruit, which is probably a consequence of secondary infections. These spots sometimes give the appearance of a burn from plant protection products. Root growths often appear as well and come in the form of adventitious roots at varying heights on the stem. They are produced by the plant in order to seek water that it fails to obtain from its root system. Secondary infection caused by the splashing of contaminated water droplets, for example, can bring on foliar spots and burns prior to wilting. On fruit, visible effects can include the appearance of cankers with a black center surrounded by a whitish halo, also known as “bird's eyes”. Seed-borne transmission and dispersion in seedbed environments are considered to be this species main way of entering field crops where it is not present, while crop handling constitutes the main form of secondary transmission. The bacteria can remain in vegetable waste and soil for a long time if they are not properly disinfected.

Figure 10

Figure 11

214

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

2.3.2 Ralstonia solanacearum Ralstonia solanacearum, which was previously classified as Pseudomonas solanacearum, features characteristics of the genus Pseudomonas, is oxidase positive, and non fluorescent on King's B Medium. It is a bacterial species that includes several strains (five are actually known) widely spread throughout tropical, subtropical and hot regions, where it causes significant problems for many crops. There is one strain, strain 3, which can act in more temperate regions and appears to be the one that affects mainly potato and tomato plants in Europe. In short, this bacteria represents the biggest threat in temperate areas. It is responsible for bacterial yellowing in tomato and is subject to eradication in those areas where it has been detected in the European Union. Spain appears as a country in which this bacteria is not established. Given the great risk it implies to affected crops and its easy transmission via water, as well as through tubercles and plant waste, exhaustive control mechanisms exist to impede its entrance and development. It is a vascular bacteria that causes, similar to Clavibacter michiganensis subsp. michiganensis, vascular wilting in infected plants. In terms of tomato crops, symptoms include the wilting of green leaves, which initially affects the youngest ones, and rapidly affects the entire plant if conditions are optimal (Figure 12). In less suitable conditions, development can be slower and adventitious roots can appear on the stem also. Browning can be observed on vascular tissues and, following a cross section, a whitish to yellowish sap exudes from them.

Figure 12

215

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria Recognized sources of inoculum for the bacteria are infected potato tubercles and contaminated vegetable waste and soil. By means of these, the bacteria can easily travel via water flows, water splashing, and wind movement. Plant handling is a common way for the bacteria to be transmitted between plants. 2.3.3 Pathogenic plant species belonging to the genus Curtobacterium The genus Curtobacterium includes a group of Gram-positive, irregular rod-shaped bacteria that include different phytopathogenic species. Of particular interest in this case is the species C. flaccumfaciens pv. flaccumfaciens, whose vascular action produces wilting in green bean plants, which is its primary host, although it can affect other crops such as soy. The effect of this pathogen is more severe the earlier the infection begins and, besides leaf wilting, it can also produce irregular, yellowish lesions on leaves, stems and pods. This pathogen is of special interest considering Andalusia is a region protected from these bacteria, which is also included as one of the harmful organisms in quarantine that are not established in Spanish territory. Therefore, it is not a known organism in the Almeria area, but taking into consideration its seed-borne transmission capacity; controls in nurseries are of vital importance.

Important fungi in horticultural nurseries

In contrast to bacteria, there exists a wide range of fungal taxonomic groups which includes phytopathogenic fungi. Similar to bacteria, they can be classified according to their mode of action or infection site-fungi that affect the root system, the vascular system, or that are airborne.

3.1 Fungi affecting root system and crown This group contains a long list of genera and fungal species that can act by altering root system quality. Several species among them worth highlighting belong to the genera Pythium, Phytophthora, Rhizoctonia and Olpidium, although there are others with some incidence such as Monosporascus cannonballus or Thielaviopsis bassicola. It is necessary to clarify that oomycetes, the group which the genera Pythium and Phytophthora belong to, are currently excluded from the fungus kingdom and are considered part of the protist kingdom. However, for the practical purposes of the presentation of this topic, in this section they will be treated as fungi, the same way they traditionally have been. 3.1.1 Pathogenic plant species belonging to the genus Pythium One of the most important oomycetes in nurseries, because its primary and most notable effect occurs in seedlings, belongs to the genus Pythium, included in the family Pythiaceae, order Peronosporales. The genus Pythium encompasses numerous species, some of which are polyphagous (P. ultimum, P. debaryanum, and P. aphanidermatum). They generically cause a lack of germination, damping-off and seedling wilt. These species are further characterized by the presence of strangling and rotting of crown and roots, accompanied by rapid wilting of

216

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria seedlings. In general, plants become stronger after the growth of the first real leaves, but they can die if they are already infected. In cucumber crops, some attacks have been observed on plants in a state of development following the seedling state, causing soft rot in the crown (Figure 13). This affects a great number of crops, among which are pepper, aubergine, tomato, cucumber, melon, watermelon, green bean, beetroot, and lettuce. This oomycete is saprophytic and characterized by forming a fast-growing mycelium that produces sporangia. These, in turn, produce zoospores that are capable of dispersing by swimming in water. It also forms oospores in its sexual stage which persist in adverse environmental conditions. It commonly enters growing areas by means of sick plants, contaminated substrata, contaminated water, and infected seeds.

Figura 13

3.1.2 Pathogenic plant species belonging to the genus Phytophthora Similar to Pythium, the genus Phytophthora belongs to the family Pythiaceae. Among other factors, it differs from Pythium because of its slower growth in culture media, typically lemonshaped sporangia, and lower saprophytic capacity. This genus includes numerous pathogenic species with a vast diversity in terms of their modes of action and the wide range of hosts they affect. Their symptoms include rotting of plant roots and crown during periods of growth or production, fruit rot, and the eventual appearance of some very severe diseases such as

217

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria phytophthora blight in peppers (P. capsici), or mildew in tomatoes and potatoes (P. infestans), which will be addressed in the section on mildew. P. parasitica, P. capsici, P. megasperma, and/or P. drechsleri have been identified as capable of affecting the crowns on peppers, melons, and courgettes. P. parasitica affects tomato crops particularly after transplant, causing rapid watery crown rot and a high rate of plant death (Figure 14). P. capsici affects peppers and manifests as Phytophthora blight causing crown rot accompanied by a systematic attack on roots that leads to sudden plant wilting without yellowing and eventually death. Its attack on plants can occur during any stage of plant development, but its critical period for symptom manifestation is during fruiting.

Figure 14

The bacteria is mainly dispersed in water and contaminated water. It is able to remain in vegetable waste and soil between growing seasons, in addition to having multiple intermediate hosts. 3.1.2.1

Rhizoctonia Solani

The species Rhizoctonia solani is relatively important among fungi that affect root systems. It is also a polyphagous fungus and has a wide range of host plants (melon, cucumber, watermelon,

218

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria tomato, pepper, green bean, lettuce, etc.). It causes damping-off and seedling wilt, in addition to rotting with crown cankers and damage to stem, root and even fruit. This fungus lives in soil as a saprophyte and its resistance structure allows it to survive in crop waste. It is typically found in most cultivated soils, where it enters plants from the substrata or contaminated plants from nurseries. The most visible symptom in nurseries is seedling wilt, which can be confused with a symptom caused by Pythium, but in this case brown cankers can appear at the stem base. Cucurbit seedlings exhibit strangling and both crown and root rot, whereas in solanaceae it causes softening in the basal stem. In green beans it can attack before or after seedlings emerge from soil and causes crown cankers and eventually necrosis in the crown and roots. In general, it can be said that tissues during juvenile stages are more susceptible to the fungus than in adult plants, but its effects can still persist, especially in plants infected during their initial development stage. Crops such as lettuce are very susceptible throughout their entire lifecycle and experience crown cankers and leaf rot mainly in the basal area, where blackening occurs (Figure 15).

Figure 15

219

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

3.2 Fungus affecting vascular system There are few fungal species that specifically affect the vascular system of horticultural plants: Fusarium oxysporum and Verticillium dahliae or V. alboatrum. However, in the Almeria area they are limited to practically only the first species, F. oxysporum. 3.2.1 Pathogenic plant species belonging to the genus Fusarium The genus Fusarium includes various pathogenic plant species, among which is Fusarium oxysporum and its different formae speciales (F. oxysporum f.sp. melonis in melon, F. oxysporum f.sp. niveum in watermelon, F. oxysporum f.sp. cucumerinum in cucumber, F. oxysporum f.sp. lycopersici and F. oxysporum f.sp. radicis-lycopersici in tomato). These formae cause an infection in the vascular system by obstructing vessels. Symptoms include leaf yellowing and plant wilting, accompanied by vascular necrosis. This fungus is characterized by a hyaline mycelium with numerous branches where microcondia, macrocondia, with between 3 and 5 septate are produced. Other characteristics are its resistance spores called chlamydospores and its ability remain in soil for a long time. In general, these pathogens are seedborne and feature low yet significant transmission rates, making them one of the primary sources of inoculum. Moreover, plants can be affected during different stages of development: before emerging (as a seedling in a seedbed) or as an adult plant. However, it is more common for the disease to advance progressively and be most visible during fruit swelling. 3.2.1.1

Fusarium oxysporum f.sp. melonis

Quite frequently causes death in melon seedlings with characteristic symptoms of Fusarium wilt. In this crop, as well as in watermelon infected by F. o. niveum, drooping and necrosis of leaves are observed, which is symptomatic of an initial "one-sided wilt" that eventually spreads. This is accompanied by stunted growth and the browning of vascular tissues (Figure 16). Relating specifically to melon, symptoms of intense yellowing appear in addition to the presence of a necrotic streak that advances along the stem and petioles and which is sometimes accompanied by reddish sticky secretions in the lower portion of the stem. The incidence of F. o.niveum on farm crops rose so high that it managed to compromise the entire watermelon crop in the Almeria area, but fortunately this was reversed thanks to the utilization of pumpkin grafts resistant to this fungus. Presently, all of the watermelon crops in the greenhouse area of Almeria are grafted. In cucumber, F. o. f.sp. cucumerinum also causes vascular wilt both in seedlings and adult plants. This particular disease produces long necrotic streaks, along with symptoms of yellowing in basal leaves, browning of the vascular system and wilting. Infection can take place at any age of the plant resulting in damping-off, seedling wilt and, in early stages, wilting and death of plants in transplanting.

220

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 16

3.2.1.2

Fusarium oxysporum f.sp. lycopersici

F. o. f.sp. lycopersici is responsible for Fusarium vascular wilt in tomato. In this case, the disease is characterized by yellowing, primarily on basal leaves, followed by wilting without defoliation, accompanied by browning of vascular bundles. This fungus is not very common, not to say inexistent, in the horticultural crops along the Almeria coast; this is most likely because the area does not possess the climate conditions necessary for the disease to propagate. On the other hand, radicis-lycopersici, whith is a forma especiali of Fusarium oxysporum, is very common in the greenhouses of Almeria. 3.2.1.3

Fusarium oxysporum f.sp. radicis-lycopersici

F. o. f.sp. radicis-lycopersici is responsible for a type of Fusarium wilt in tomato that affects mainly the root system. Visible signs of one-sided chlorosis on leaves do not usually appear, at least until advanced stages of the disease, but a more evident symptom is plant wilt at the hottest part of the day. This wilting subsides at night, but eventually causes plant death in many cases, especially during the fruit swelling stage (Figure 17) when the plant is loaded with fungi. Another characteristic of this fungus is that is causes browning of the plant crown and root system.

221

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 17

3.2.1.4

F.o. f.sp. lactucum

Is responsible for the Fusarium wilt in lettuce and can cause wilting and death in seedlings. Affected plants in this crop exhibit a characteristic brown stripe that extends from the main root to the crown cortex. Other species worth mentioning in the genus Fusarium include F. solani, which can be very important in certain cases. One such case is that of F. solani f.sp. phaseolicola, which is one of the most widespread fungi in the world as an agent of root necrosis in green beans. Another species is F. solani f.sp. cucurbitacearum, which is causing significant damage at the crown level of courgette plants in the Almeria area.

3.3 Airborne fungi This section focuses on fungi that affect the aerial part of plants and are mainly airborne in their transmission (handling, wind, water splashing, etc.). The examples included in this section are considered to be of great importance. Notwithstanding, it is obviously known that the list of other fungi is quite long and there are very common examples such as Sclerotinia sclerotiorum, but they are scarcely present in the Almeria area. As a result, due to the focus

222

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria and limited space of this chapter, they will not be addressed. However, it must be noted the fungi not included herein may be very relevant in other regions of the continent. 3.3.1 Didymella bryoniae Didymella bryoniae (Mycosphaerella melonis) is responsible for sticky stem blight in melon, cucumber and watermelon. Damage caused by this pathogen can begin in nurseries, where circular spots appear on cotyledons and advance to the stem, where lesions emerge that eventually dry out the plant. In adult plants the disease produces lesions on the stem, generally at the stem base, which becomes dark and black, corresponding to the perithecien of the fungus. These lesions can also frequently exude a sticky black sap (Figure 18). Watery patches appear on the leaves and expand to cover large areas, eventually causing leaves to die. Also visible on leaves are fungus pycnidia and perithecien (Figure 19). The effects on fruit can be quite severe, primarily on cucumber and courgette. The fungus penetrates mainly through the stem scar causing the latter to lose volume and eventually rot.

Figure 18

Figure 19

3.3.2 Botrytis cinerea Botrytis cinerea (Pers)., an asexual form of Botryotinia fuckleliana, which is one of the most important airborne fungi in the Almeria area and also worldwide. This is largely due to its polyphagous nature (it attacks a large number of plant species), rapid dispersion, challenging control (strains currently exist that are resistant to all products that initially allowed its chemical control) and severe effects. It can affect all plant organs, above all if the plant is weakened or damaged, ultimately causing plant decay. In nurseries the fungus produces crown and stem rot that lead to the wilting and drooping of seedlings, whereas in adult plants it attack stems, leaves and fruit. The fungus develops on lesions located on the stem (Figure 20), where it produces rot and stem wilt. Brown lesions appear on leaves and flowers, while it

223

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria produces patches or soft rot in fruit (Figure 21). In all cases, this fungus is usually easy to identify when lesions develop and when in the presence of moisture, mainly because a characteristic grey powdery mycelium forms on affected organs. Disease incidence for this fungus is greater in the early phenological stages of plants, particularly in the months of December and January as they offer the adequate climate conditions for its development (temperatures between 7 - 24 ⁰C and relative humidity over 90 %).

Figure 20

Figure 21

3.3.3 Diseases caused by oidia Oidia comprise another airborne pathogen that must be considered as a priority in the horticultual crops of Almeria. The term refers to a group of fungus species belonging to the family Erysiphaceae, order Perisporales, class Ascomycetes. They are characterized mainly by the fact that they cause a powdery mould to appear on plants, leaves and stems. It is usually whitish in colour giving it an ashy appearance. Oidia can be differentiated with regard to the crop families that they affect. As far as cucurbits are concerned, the most frequently involved fungi are Podosphaera xanthii (previously known as Sphaeroteca fuliginea) and Golovinomyces cichoracearum (until recently identified as Erysiphe cichoracearum), but the most prevalent in the Almeria area is Podosphaera xanthii. This disease, which is present worldwide, attacks at any stage of plant growth and produces a powdery white mildew on leaf surface (Figure 22) that expands until it causes the drying of leaves and stems. These fungi develop externally and are apparently not affected by relative humidity.

224

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 22

Golovinomyces cichoracearum is another agent responsible for oidia in lettuce, which it normal affects when the plant is in its adult stage. In green beans oidia are caused by the species Erysiphe polygoni, which produces a white layer that covers leaf surfaces that eventually turn powdery. This leads to interveinal chlorosis in leafs. In regard to solanaceae, the most common causal fungus is the species Leveillula taurica. The symptoms of this disease first begin on the top side of leaves, which exhibit yellow patches whose centers eventually necrotize (Figure 23). The underside of leaves reveals fluffy white patches produced by the fungus that are bound by leaf veins. The development of the disease leads to wilting and leaf detachment, ultimately resulting in significant plant defoliation. In tomato, G. cichoracearum is also known to produce powdery white patches in the Almeria area.

225

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 23

3.3.4 Diseases caused by mildew Finally, also relevant are airborne fungi encompassed by the generic term “mildew”. This group includes fungi from the order Peronosporales, which includes species such as Pseudoperonospora cubensis (agent of mildew in cucurbits), Phytophthora infestans. (In solanaceae), and also Bremia lactuae (in lettuce). Pseudoperonospora cubensis, the causal agent of mildew in cucurbits, exhibits a hyaline mycelium that develops intercellularly inside affected tissue. Emerging from the mycelium are the sporangiospores where sporangia are formed that produce the fluffy purplish-grey patch that is visible on the underside of leaves. The effect of this fungus in greenhouses is mainly observed in melon and pepper crops, but also in watermelon and courgette. In cucumber, symptoms are generally observed when the plant has reached its adult stage, producing light yellow patches on the top side of leaves and oily on the underside. They are also angular in shaped since they are bound by the leaf veins (Figure 24). These patches eventually dry and necrotize. In cucumber, it is rare to observe attacks on cotyledons and true leaves during the first stages of development as they are quite resistant to the fungus attack. Symptoms in melon can occur early on, even in nurseries. The first lesions that form are generally small translucent irregular patches that are light green and surrounded by a yellowish halo. As they

226

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria develop, they dry and necrotize. The downy material of the fungus can be seen on the underside of the leaf. The patches on watermelon are similar to those on cucumber, but they are smaller in size and are usually near the leaf edges.

Figure 24

Figure 25

Mildew in tomato and potato, caused by Phytophthora infestans (Mont de Bary), mainly affects adults plants but can be a dangerous disease in nurseries located in areas where it is not endemic. Symptoms in affected plants begin at the edges and apex of leaves, starting with the lower ones. Initially yellow patches appear that later turn brown and necrotize in the center. A brown canker forms on the stem which can eventually girdle it completely and wilt the portion above it. In this situation fruit is also affected and reveals a necrosis that advances on the fruit itself (Figure 25), sometimes exhibiting growth rings. In humid conditions this area can soften and a downy mycelium can emerge. Mildew in lettuce caused by Bremia lactucae (Regel) is one of the most dreaded diseases for this crop. It can attack lettuce at any stage of its life cycle. If climate conditions are adequate in nurseries and there is high plant density, damage can be severe. The first symptoms appear in cotyledons where yellowing occurs and progresses until eventual death. Seedlings that are affected are weakened and as a result are more susceptible against any adverse factor, whether biotic or abiotic. During subsequent stages, the mildew affects external leaves, producing angular patches bounded by leaf veins. The leaves themselves yellow and necrotize from drying or rotting, depending on whether humidity is low or high. The underside of the leaf reveals the characteristic downy white patch of the fungus, which germinates and grows optimally at temperatures between around 15-20 ⁰C and with relatively high humidity. There are other fungi with relatively high incidence in the Almeria area, whether it be in nurseries, on farms, or following harvest. Their names are worth remembering even though they are not discussed in detail in the present chapter. These fungi include: Alternaria sp. (which is the case of A. solani in tomato or Alternaria cucumerina in cucumber) normally involved in producing spots on leaves and stems, Stemphylium sp., which is the causal agent of leaf spots in tomato, mistaken for those of Alternaria, and which is gradually becoming a very

227

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria important disease in this crop, similar to Fulvia fulva - an agent also causing spots in tomato and very widespread in the Almeria area, Cladosporium cucurbitacearum is also becoming more relevant among cucurbits and causes leaf and fruit spots, and Monosporascus cannonballus, whose importance is particularly notable on farms that have repeated numerous crop cycles with melon or cucumber, non-stop, for years.

Important viruses in horticultural crops in Almeria

Viruses are microorganisms which different to the rest of living beings. This is because they are non-cellular organisms which use their hosts’ cellular machinery to multiply, they are therefore obligatory parasites. They can be classified according to the same characteristics; structure, shape, chemical make-up, genome, hosts, etc. From a practical point of view the epidemiological aspects of viruses such as their transmission media, and the symptomatology they cause may be aspects to be taken into account. In fact, one of the traditional ways of classifying a virus is based on its transmission media, as this may be determinant in the establishment of a means of control for said virus. In Table 1 annexed, the main viruses found in horticultural crops in Almeria are listed according to their transmission media.

4.1 Viruses transmitted by contact There is a long list of viruses that can be transmitted by contact, some of the most serious of which are included in the Tobamovirus genus, due to the damage they cause to different horticultural crops. As well as the tobamovirus, there are others which are transmitted by contact amongst which the PepMV virus stands out. It is currently one of the main viral diseases affecting tomatoes, not just in Europe but also worldwide. The common characterstic of all these viruses is that they can be transmitted by direct contact between plants, with contaminated soil or tools, utensils and even growers or labourers’ hands or clothes, all of which could have been infected during the handling of the plants whilst carrying out tasks such as pruning, thinning, fruit picking or just by brushing through the plants. 4.1.1 Tobamovirus Within the Tobamovirus there is a group of viruses which, as well as being transmitted by contact are made up of viral particles which are both very stable and very resistant to physical and chemical factors. The virus can remain on infected land for a long period of time, where both soil and water which have been contaminated by infected vegetable waste can also become sources of infection. Its description can be carried out jointly because it shares many characteristics regarding the nature of the viral particle, transmission media, inoculum sources and, above all means of control. Amongst the virus of interest in the greenhouses of Almeria the following are of particular importance:   

ToMV: Tomato Mosaic Virus which affects tomatoes and cucumbers. PMMV: Pepper Mild Mottle Virus affecting peppers TMGMV: Tobacco Mild Green Mosaic Virus in peppers and aubergines

228

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 

CGMMV: Cucumber Green Mottle Mosaic Virus in Cucurbitaceae

The tomato mosaic virus ToMV causes very varied symptoms according to the strain of virus which infects the plant and the tomato variety affected. Generally speaking the leaves have a light to dark green mosaic which is at times so mild that it goes unnoticed (Figure 26) However, at times it can be a brighter chlorosis, or even necrotize. The stalks also have necrotic marks. Symptoms on the fruits can range from circular necrotic marks to complete fruit necrosis. There are also varieties where no symptoms appear on the fruits. The earlier a plant is infected the greater the degree of development delay. In peppers, both ToMV and PMMV, cause mainly a mild, light to dark green mosaic on leaves which is rarely more pronounced. All these symptoms may go unnoticed but that is not the case with fruit symptoms. These are much more obvious due to the serious deformities which are normally accompanied by blistering and sometimes grooves or necrosis. It can also delay plant development. These viruses can only be distinguished through laboratory analysis.

Figure 26

Figure 27

TMGMV has been detected in both peppers and aubergines. In aubergines the main symptoms observed are foliar necrosis and deformities accompanied by necrosis with fruit splitting (Figure 27). In peppers the most noteworthy symptoms are fruit necrosis and deformity. CGMMV also affects different cucurbits, mainly cucumbers, melons, watermelons and courgettes in our area. Several races have been detected as well as the crops they affect and the symptomatology. In cucumbers the symptoms are mottling of young leaves and the appearance of star-shaped patches (Figure 28). Nerve constriction also occurs which leads to leaf blistering. Symptomology in fruit varies greatly from asymptomatic fruits to fruits with more or less mild mottling, blistering and serious deformities (Figure 28). In watermelons there is a mild leaf mosaic (Figure 29) and it can lead to the internal rotting of mature fruit. In melons foliar mottling, dwarfing and a drop in yield can occur. In courgettes the same star shaped patches as in cucumbers appear as well as very slight leaf and fruit blistering.

229

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 28

Figure 29

All the viruses mentioned are transmitted mainly by contact: brushing between plants, during handling, through the soil or irrigation or rain water. There is a limited range of wild hosts. In the case of ToMV, PMMV and TMGMV it can be found on some wild solenacea. CGMMV, as well as in the crops mentioned, can also be found in Lagenaria siceraria. Regarding primary sources of infection; seeds that have not been adequately treated, infected soil, infected vegetable waste and wild host plants. Depending on environmental conditions these viruses can remain active in vegetable waste for periods ranging from months to years. 4.1.2 The Pepino Mosaic Virus PepMV The Pepino Masaic Virus (PepMV) is a virus which affects tomato crops (Solanum lycopersicum), sweet cucumbers (Solanum muricatum), and some wild solinacea but it does not affect cucumbers (Cucumis sativus). It appeared for the first time in 1999 in tomatoes in England and the Netherlands, spreading from there to the whole of the European continent and Mediterranean Basin as well as South and North America. It can cause mild to severe symptoms depending on the viral race, the crop variety and the climatic conditions. Symptoms are apparently milder during sunnier periods and more visible when the days are short and cold. Leaves may range from slightly mottled or with a mild mosaic to severe chlorosis, blistering (Figure 30), shoestringing and what is known as “arrowhead leaves”. Regarding the fruits, symptoms can range from none at all to a characteristic mottling (Figure 31) and inadequate ripening, a symptom which can also be associated with other nutritional problems, TIR, lack of light, etc. Other symptoms described are growth reduction, plant shoestringing and, at times, collapse. PepMV is a virus which is transmitted by contact; tools, machinery, labourers’ hands and clothes, between or among plants, etc. Seed transmission has been established to be very low, from 0.005 % to 0.05 % in treated seeds. It also appears to be soil and irrigation water borne. Although this virus can remain active for less time than the tobamoviruses it can survive for months, between seasons. It can be found in infected vegetable waste, uprooted plant roots

230

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria or in fruits, the commercialisation of which is also considered a possible means of dispersion for the virus. Its survival, for at least some weeks, has been established in other materials.

Figure 30

Figure 31

4.2 Thrips-borne viruses 4.2.1 Tomato spotted wilt virus (TSWV) The main virus transmitted by thrips is the “tomato spotted wilt virus” or “spotted” it is a major viral disease affecting pepper and tomato crops in Almeria’s greenhouse areas. When it was introduced during the eighties it caused serious damage to our crops but, it was contained by timely the development of resistant varieties. However, there is now a new strain of the virus which is able to overcome the resistance in peppers (not so in the case of tomatoes), and which is being contained thanks to the biological control of the vector. In tomatoes it causes dark golden necrotic marks on the leaves which give them a tanned appearance. It can deform the heads and reduce development in plants are infected at an early stage. It causes irregular ripening as well as chlorotic and necrotic rings in fruits (Figure 32). In peppers it causes concentric, chlorotic rings or arabesque shapes on leaves (Figure 33), which can also necrotize. It can deform young shoots, cause dwarfing in heads and retard plant growth. It also causes ring shaped marks on the fruits.

231

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 32

Figure 33

In our province it can also be a serious problem for lettuces, causing mainly necrosis, usually more present on the outer leaves. Many other crops are affected by this virus with symptoms similar to those described. Cucurbitaceae are, in principle, unaffected by the virus. It is transmitted through the bite of an infected thrips Frankliniella occidentalis although thrips is not infectious at every stage of its development. It gets the virus in its larval stage when it feeds off the sap of an infected plant but will only be able to transmit it when they become adults. An adult thrips is unable to acquire the virus at that stage. In short, the larvae acquire the virus but cannot transmit it and the adults transmit it but can´t acquire it. It is quite an unstable virus which cannot survive long in vegetable waste and only for a question of minutes or hours in the atmosphere. It’s transmission by seed or natural contact has not been reported. Given its instability and its dependence on thrips for transmission, it may be considered that the main reservoir and primary source of infection for the virus is any one of its uncountable hosts (horticultural crops, ornamentals, weeds, etc.).

4.3 White fly-borne viruses White fly in general, and particularly Bemisia tabaci, is one of the main pests affecting horticultural crops in the province of Almeria. It is important due to the fact that it can transmit viruses which have very serious impact in our province, added to the damage that they themselves can cause. In tomatoes they can transmit TYLCV (which can also affect beans) TocV, TicV, or ToTV, the two latter still virtually unknown in our province. It transmits CSYDV and CVYV in Cucurbitaceae. 4.3.1 Tomato yellow leaf curl disorder (TYLCD)

232

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria The TYLCV virus is one of the main viral infections affecting tomato crops in Almeria. It arrived in this area in the early 90s together with Bemisia tabaci, causing havoc in tomato crops. There is a coextistance with the virus due to the development of tolerant varieties although there is still a high incidence of early infection with high temperatures. These tolerances are threatened due to the appearance of new viral races, or recombining strains (blends of old ones) and TYLCD is showing no shortage of those. This is why we often refer to the disease (TYLCD=Tomato yellow leaf curl disease) and the complex of geminiviruses associated with it (TYLCSV, TYLCV, TYLCKaV, TYLCGuV, TYLCCMV, etc). This genetic diversity entails biological variability which appears in the varieties of tomato in is able to infect, whether it infects beans or not, etc. The symptoms it produces in tomato crops are mainly upwards leaf curling, more noticeable in young leaves, accompanied by chlorosis around the whole edge and delayed development of leaflets above all in the apical area (Figure 34). The sprouts are stiff and erect and sometimes violet in colour. There is a stop in plant development and it resembles more a bush. The virus affects flowering and thus plant production. When infection takes place at an early stage production loss can reach very high levels.

Figure 34

TYLCV is transmitted only both effectively and specifically by the Bemisia tabaco white fly. It is a type of persistent transmission in which the white fly acquires the virus by feeding between

233

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 15 and 30 minutes on an infected plant, even better if it feeds for several hours. Following a latency period of several hours the white fly can begin to transmit the virus. The virus can be transmitted by the vector for the rest of its adult life. This transmission ability is not inheritable. No other form of transmission, be it mechanical or by seed, is known and its persistence in vegetable waste is limited. With a relatively low number of natural hosts, apart from tomatoes and beans it has only been found in Solanum nigrum y Datura stramonium, the transmission of the virus is closely linked to Bemisia tabaci, which is important when it comes to establishing control measures 4.3.2 Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TiCV) Tomato chlorosis virus (ToCV) is a viral infection which is on the rise in tomato crops in our province and is also occasionally detected in peppers. It is present worldwide and was reported in Spain in 1997 in the southeast. The Tomato infectious chlorosis virus (TiCV) is now also reported to be present worldwide. It was reported for the first time in 2001 in Castellón and Alicante and has since spread widely to the Spanish Levant, except for Almeria for now, due to the fact that its vector, the white fly Trialeurodes vaporariorum, has hardly been detected here. The symptomatology of both viruses, ToCV and TiCV, is quite similar. There is an internerval yellowing which affects the central/lower area of the plant (Figure 35). At times this chlorosis can turn brown or tanned until it necrotizes above all in basal leaves. Said leaves may roll up, become thicker and more brittle and the plant generally loses colour and shine. This symptomatology can easily be confused with nutritional disorders, chemical toxicity or natural leaf senescence. There may be some delay in plant development and fruit ripening, although the fruit is perfectly apt for sale. TiCV may show more severe symptoms than ToCV. ToCV is transmitted by different species of white fly, Trialeurodes vaporariorum, Trialeurodes abutilonea, y Bemisia spp. TiCV is transmitted by the white fly species Trialeurodes vaporariorum but not by Bemisia tabaci. None of them is transmitted mechanically. Different wild hosts for these viruses have been reported which can be both reservoirs as well as infection sources for said viruses due to the fact that they do not survive long in vegetable waste.

234

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 35

4.3.3 Tomato “torrado” virus (ToTV) Its symptoms were first described in Murcia (Spain) in 2001. However, it was not until 2007 when Verbek et al., isolated and described the virus. This virus has spread along the Spanish Levant and has reached as far as the Canary Islands where it has also caused serious damage. However, for now, although there has been no important appearance the virus in Almeria, it has been reported occasionally. It causes aerial level symptoms which, as the disease progresses, make the plant look burned or “toasted” (“torrado” in Spanish). The symptoms begin with the appearance of chlorosis with necrosis at the base of the leaflet, patches which go from the base of the leaflet to the apex, with partial or total deformity of same (Figure 36). Necrosis and deformities in stems, petioles and peduncles present. The plants show a reduction in development with dwarfing and head deformation. The fruits showed serious “zip” necrosis and cracking (Figure 37).

235

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 36

Figure 37

White fly (Bemisia tabaci and Trialeurodes vaporariorum) appear to be a possible vectors, there is still much data regarding how this virus is transmitted to be defined. What is known about the virus is that it is present in several wild plant families; Amaranthaceae, Caryophyllaceas, Chenopodiaceae, Cruciferae, Malvaceae and Polygonaceae. 4.3.4 Cucurbit yellow stunting disorder virus (CYSDV) CYSDV, or the “Yellowing Virus”, as it is known locally, was first detected in the United Arab Emirates in 1982 spreading to all the Mediterranean Basin, Europe and America. It was first detected in our country, in Southeastern Spain, in 1991. Its most characteristic symptom is an internerval yellowing which starts with older leaves first and progresses to younger ones, both in melons and in cucumbers (Figure 38). No symptomatology is present in the fruits nor does it affect plant development. There has been reported, however, a loss in production. With regards other cucurbits such as courgettes and watrermelon, they have been described as virus hosts but, for the moment in our area, hardly any symptoms have been observed in these crops.

236

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 38

This virus is transmitted exclusively by Bemisia tabaci semi-persistently. That is to say that the flies need to feed for an extended period of time (hours) to acquire the virus and, after a latency period during which they do not transmit the virus until they become infective, which they will continue to be for 9 days. Fortunately, transmission efficiency is not very high and only 3 % of infective flies transmit the virus to a melon plant. There are few wild plant reservoirs for this virus because the range of natural hosts for the CYSDV is limited to the cucurbtaceae (melons, watermelons, cucumbers, marrows, and courgettes), alfalfa (Medicago sativa), lettuce (Lactuca sativa) and beans (Phaseolus vulgaris), mainly. Given that it is not a stable virus able to survive in the atmosphere or vegetable waste, these reservoirs are important as a possible source of virus. 4.3.5 Cucumber vein yellowing virus (CVYV) The Cucumber vein yellowing virus (CVYV) is the other important virus transmitted by B. tabaci in cucurbitaceae. It was detected in Spain for the first time in 2000 and is located in countries in the Mediterranean Basin. In Almeria it causes symptoms in cucumber leaves and fruit. The most typical sympomatology of this virus, in cucumbers, is a yellowing of the apical area leaves. A general yellowing of the plant is also possible, together with delayed development, smaller fruits mottled leaves and a mosaic on the cucumber fruits. Sudden death of the plant

237

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria may also occur. In courgettes, a milder yellowing of the leaf nerves may occur too. With watermelons, symptoms of mild chlorosis on the leaves which may even go unnoticed. However, watermelon plants may suffer from generalized fruit necrosis and splitting with this virus.

Figure 39

CVYV is also semi-persistently transmitted by this fruit. In this case the persistence of this virus in white fly is significantly lower, around 6 hours. It has a range of hosts which is maily restricted to cucurbitaceae, both cultivated and wild. Infection of some members of other families has also been demonstrated as is the case with; Solanaceae, Asteraceae, Malvaceae and Convolvulaceae. These host plants can act as reservoirs and sources of inoculation for the virus.

4.4 Aphid-borne viruses Viruses transmitted by aphids have historically caused very serious problems for open-field and greenhouse horticultural crops alike. In past decades they were kept under control by the use of chemicals against the vectors and virtually insect-proof greenhouses. However, while the widespread introduction of biological greenhouse-pest control has improved the results regarding white fly and thrips, it has not been so with aphids. This is the reason why some cases of this type of virus are reappearing. Amongst the different virus we can find in our area which are transmitted by aphids we can find cucumber mosaic virus (CMV), very serious for most of the crops, the potato virus yellow (PVY) for solanaceae, and the zucchini yellow mosaic virus (ZYMV) Amongst the different viruses transmitted by aphids to be found in our province the following stand out; the cucumber mosaic virus (CMV), seriously affecting most crops, the Y potato virus (PVY) affecting solanaceae and the zucchini yellow mosaic virus (ZYMC), the watermelon

238

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria mosaic (WMV), papaya ring-spot virus (PRSV) in cucurbits, together with the yellowing virus in cucurbits which is transmitted by aphids (CABYV) and has just recently been discovered in the area 4.4.1 Cucumber mosaic virus (CMV) The cucumber mosaic virus (CMV) is a virus which is present worldwide and has a large number of host plants. It affects the majority of horticultural crops in our area. There are different races of virus which are responsible for the appearance of different symptoms. Symptoms in tomatoes can range from mild to severe. There are some races which are not very virulent and cause a mild mosaic, causing only slight damage to leaflets, shoestringing, as well as internal necrosis in the apical area of the first fruits. More aggressive races may have more pronounced symptoms, internerval chlorosis with necrosis in more or less open areas of the leaves. Said leaves may curl outwards over the petioles and the stalk, which can also show necrotic marks. The illness advances from the apical area to the lower area. Deformities and more or less necrotic areas may appear on fruits (Figure 40). The disease also affects plant development by causing a shortening of internodes and it acquires a stumpy appearance. In any case, it is important to take into account that, although the disease may be very harmful to the plant it is not common for a high dispersion between plants to take place in the greenhouse due, above all due to the control of the vector.

Figure 40

239

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria In peppers yellowing together with leaf curl, shortening of internodes and the appearance of some necrotic patches green rings on old and yellowing leaves. Shape and colour alterations may appear on leaves, with discoloured rings or necrosis and also fruit drop. Shallow and deep necrotic cuts can also appear. In cucurbits, mainly cucumbers, melons and courgettes, they cause leaf deformity, leaf area reduction, deformity and a yellowy green mosaic. In the fruits, mainly courgette and cucumber it causes deformities with depressions and holes as well as hardening of same and reduced fruit set. The appearance of mixed infections with other viruses is common, mainly potyvirus such as PRSV, ZYMV or WMV. In leguminous crops it attacks mainly beans and broad beans. In beans it shows mosaics on leaves with discolouring at the edges of the nerve structure and foliar deformities. In broad beans there may be reddish colour patches on the underside of the leaves which can lead to necrosis and leaf wilt. It is transmitted in a non-persistant way by numerous species of aphid, especially Myzus persicae, Aphis gossypii, A. fabae and Macrosiphum euphorbiae. The virus is acquired by the insect from an infected plant by sap “tasting”. It is enough for it to on the plant for a minute for it to be able to transmit the virus to another plant with no need for a latency period. The ability to transmit the virus lasts for about four hours, as long as the viral load acquired during feeding lasts. After that period it can become re-infected by feeding off an infected plant again. The number of host plants of this virus is very high, in excess of 1000 vegetable species which include both cultivated varieties and wild plants. They are both reservoirs and inoculums sources of the virus. Some, very limited, transmission via seed has been reported in some leguminous plants and cucurbits but none at all for tomatoes, peppers, courgettes, cucumbers or melons. 4.4.2 Potato virus Y (PVY) The Y potato virus is the type species of the Potyvirus genus. It is a virus which is present worldwide and naturally affects, and almost exclusively, solanaceae crops namely peppers, tomatoes, potatoes and tobacco. There are different races of virus which can be differentiated by the symptomatology they cause, their ease of transmission and their host specificity. Symptomatology in tomatoes is not usually very pronounced. It can range from a virtually unnoticeable mosaic coupled with slight leaf deformities to some limited internerval necrosis on leaves around the middle of the plant. Fruits do not usually show symptoms.

240

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 41

In peppers the damage is, in general, more serious. It can range from a slight internerval mosaic to a marked necrosis of the nerves on the underside of the leaf (Figure 41) and above all on the youngest leaves, which can be deformed, in the case of necrogenic strains. It can show necrosis in the stem. There may be necrosis and greater or lesser deformities on the fruits. Plant growth may be reduced above all in the case of early infection. PVY is a virus transmitted, non-persistently, by over 25 species of aphids; (Myzus persicae, Aphis gossypii, A. spiraecola, A. fabae, Macrosiphum solanifolii, M. pisi, etc.). 15 - 60 seconds feeding-time on an infected plant is enough for an aphid to transmit it to a healthy one for which it requires an inoculation time of 30 to 60 seconds. It can retain this capacity for a maximum of 24 hours. It can become ineffective again if it feeds off an infected plant again. No transmission by seed has been detected. There are several wild species, as well as the cultivated ones, such as Solanum nigrum, S. dulcamara, Cirsium spp. Portulaca oleracea, etc., which are natural hosts for the virus and can act as reservoirs and sources of inoculum for the virus. 4.4.3 Zucchini yellow mosaic virus (ZYMV) Zucchini yellow mosaic virus (ZYMV) is a potyvirus transmitted by aphids which affects a very limited range of hosts, almost exclusively cultivated cucurbits, and is present worldwide.

241

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 42

In courgettes it can start with a discolouring of the leaf nerves, the yellowing of large areas of the leaf intermingling with dark green areas, blistering and shoestringing to a greater or lesser extent (Figure 42). It affects the general development of the plant and the fruits show deformities and cracking. In many cases it is indistinguishable from affects produced by the PRSV virus. Some more or less virulent strains can cause a mild leaf mosaic and no symptoms on the fruits. In cucumbers there is discolouring of the nerves followed by patches of varying intensity, deformities and blistering of the leaf, plant development delay and light coloured patches on the fruit. The disease can be more serious in melons, causing discolouring of leaf nerves, yellowing, mosaics, deformities and blistering as well as uneven plant growth. The fruits can show mosaics, external russeting cracking and internal patches and necrosis. In watermelon the most common symptoms are well defined leaf mosaics and lack of plant development. This virus, as with the potiviruses explained below, is transmitted by many aphid species Myzus persicae, Aphis gossypii and Macrosiphum euphorbiae. The way of transmission for all of them is what we call “non-presistant transmission”. The virus is acquired by the vectors by “sap tasting” the plant, so to speak. A one minute tasting session is sufficient for the virus to be transmitted to another healthy plant with no need for a lapse in time. This transmission to a healthy plant can take place in an equally short period of time. Furthermore, the aphid is only

242

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria infective for a few hours, as long as the viral load acquired during feeding lasts. It can then reinfect itself by feeding on infected plants again. Regarding plants capable of hosting ZYMV, there are hardly any alternatives to the crops already mentioned. Seed transmission is, in general, not possible although there have been reports of a very low incidence of ZYMV in courgettes, and of a very low epidemiological value. There is also some evidence of transmission capacity during pruning when the sap of one plant mixes with that of another due to the cuts made using scissors. 4.4.4 Papaya ringspot virus (PRSV) The papaya ringspot virus (PRSV) formally known as “Watermelon mosaic virus-1” WMV-1, is a potyvirus which also affects cultivated cucurbits; courgette, melons, watermelons and cucumbers, almost exclusively. The most aggressive symptoms are visible in courgettes: shoestringing, blistering and green mosaics on the leaves which are also curlier and more saw-toothed. The fruits show deformities, blistering and cracking, and also rusetting (Figure 43). In melons and watermelons there can be deformities, shoestringing blistering and chlorosis in the leaves with dark green bands in the areas next to the nerves. In both cases fruit development is reduced, there are external deformities and, above all in watermelons, pulp is discoloured. Cucumbers also show leaf mosaics and deformities together with poorly developed fruits with deformities and mosaics on the skin.

243

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 43

Regarding the transmission media and hosts, the same as was mentioned regarding ZYMV applies here. 4.4.5 Watermelon mosaic virus-2 (WMV-2) Watermelon mosaic virus-2 (WMV-2 or simply WMV) is another potyvirus which is practically indistinguishable from the previous one with regards symptomatology in cucurbits, although slightly less serious. In this case the range of hosts is a little wider than for the other two viruses It causes symptoms which are similar in different cucurbits: diffuse mosaics, light dark bands around the leaf nerves, shoestringing and leaf deformities. There is fruit loss, and these can be deformed and suffer colour changes, above all watermelons and courgettes. These symptoms can worsen seriously with the appearance of mixed infections, which are very commonplace, given the similarity of host plants and insect virus vectors. Regarding the transmission media, the same as for ZYMV can be said. It is not transmitted by seed and reported hosts are some leguminous, ornamental and wild plants

244

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

4.5 Cucurbit aphid-borne yellowing virus (CABYV) There have recently been some cases of crop yellowing reported in the absence of white fly but with the presence of aphids. These cases can be explained by the presence of cucurbit aphid-borne yellowing virus (CABYV) reported in the Campo de Cartagena (Murcia) in 2003 as the main cause of melon and courgette yellowing there and recently reported in our area. It affects the four main types of cucurbits grown in our area: courgette, melon, cucmber and watermelon. The symptoms it causes are basically yellowing and swelling of the oldest leaves and progressively the younger ones (Figure 44). Chlorosis is initially mild with discreet internerval light green patches which join up and grow clearer until the leaf becomes bright yellow except for the nerves which tend to stay green. As for the fruit there are usually no symptoms apart from production loss.

Figure 44

It is transmitted by aphids such as Myzus persicae and Aphis gossypii and it is not transmitted mechanically. As alternative hosts to those already mentioned; beetroot and lettuces as well as a number of wild plants which guarantee the survival of the virus in the countryside.

245

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

4.6 Soil vector-borne viruses As well as viruses transmitted by contact or aerial vectors, seen in previous chapters, there are other which are transmitted by soil vectors or even by soil with vectors as yet unknown. Among the ground level vectors the most noteworthy are some fungi such as the species of the Olpidium genus, as well as nematodes. In the case of the Almeria area the soil-borne virus which became particularly serious in the 1990s is known as the melon necrotic spot virus. This virus is transmitted by the Olpidium bornavanus fungus. 4.6.1 Melon necrotic spot virus (MNSV) The melon necrotic spot virus (MNSV) has been described as a melon, cucumber and watermelon pathogen although symptomology varies according to the area or climate this is justified by the presence of different viral strains. It appears to be more harmful in autumn than in spring. Melons are the most affected crop. The symptom which this virus gets its name from is a necrotic mottling of the leaves which begins as a few small chlorotic patches dotted around which quickly turn necrotic with a light/dark golden colour (Figure 45). These can end up falling out making the leaf look riddled. It can also cause a grid-like necrosis of the leaf nerves. Goldcoloured necrotic marks can be observed in the stems, petioles and peduncles. In the area of the hypocotyls, the stem base, necrosis can also be observed (Figure 46) which can be confused, if this virus is not taken into account, with the damage caused by Dydimella bryoniae (Mycosphaerella melonis) and even Fusarium oxysporum. At times, frequently in Almeria, only the symptom affecting the plant base and a certain wilting of the plant are observed. Slight browning of the vascular bundles and a smaller root system, which is light brown in colour, can also be observed. The fruits do not usually show symptoms but russeting and mottling can also appear both on the skin and in the pulp can also appear. In watermelons the disease is also similar, in some aspects, to the one suffered by melons, above all the wilting and death of plants shortly before or during harvest. Also, at times, previously chlorosis affects the old leaves and occasionally with necrosis of the hypocotyls. The fruit may have some necrotic plaques and internal necrosis visible under the skin. In the case of cucumber, although it is sensitive to the virus, it does not usually show symptoms or if it does they are very mild and do not damage the fruit.

246

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

Figure 45

Figure 46

The virus is transmitted by a fungus; Olpidium bornavanus, previously known as Olpidium radicale, by which the virus, together with the fungus, can survive in dry soil for a long period of time. It is also transmitted by seed, in this way it has spread from one area to another. However, it is considered that the heat treatment it is usually subjected to is effective as a disinfection method. The virus can also be transmitted through plant handling during pruning. Crop handling, during pruning, is also considered to be responsible for spreading the virus from plant to plant Olpidium bornavanus is an aquatic, zoosporic fungus which is easily transmitted by water, where it moves and disperses through the zoospores it produces. It is an obligatory parasite which infects a melon’s, or another host’s, roots where it reproduces by forming reproductory structures which make up said zoospores and resistant cysts thanks to which they can remain in the soil for years. These cysts are what confer the fungus its high resistance to physical treatments (temperature) and chemical (different fungicides) and make it very hard to control. The MNSV virus which multiplies in the plant joins the fungus’ zoospores at root level so infecting new roots. It is widespread in the province of Almeria and its elimination from the soil is very difficult due to the lack of totally effective treatments against it. The most that can be achieved is the reduction of the source of the inoculum. In this way the incidence of the disease can be partially controlled although not eradicated.

Disease control

The best way to control vegetable diseases is achieved using a system of integrated measures aimed at controlling the entrance, dispersion and maintenance of pathogens in crops. It must always be remembered that a good system for preventing diseases is the only way to keep control. There is a long list of chemical products available for many of the diseases mentioned however, in many cases, they are not totally effective. Furthermore there are many cases, viruses for example, for which there are no chemical treatments. Finally, there are other cases, above all certain fungi, which easily develop strains resistant to the chemical compounds and these become ineffective, a short time after they are introduced.

247

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria In addition, although every disease has its own epidemiological characteristics, it is also true that many of them have factors in common which would enable us to control several diseases simultaneously. We are, therefore, going to compile some of the recommendations regarding the general disease control as well as some particular considerations.

5.1 Pathogen access control To avoid the entrance of pathogens into the greenhouse it would, generally speaking, be a good idea to take the following measures for the majority of diseases:      

Use seeds that have been commercially treated and have their corresponding phytosanitary passport Verify the health of the seedlings from the nursery and make sure they are not carrying any of the pathogens previously described at the time of transplanting Disinfect all the tools that are going to go into the greenhouse Do not exchange personnel between greenhouses, and if necessary make sure specific clothes, and shoes, for the different greenhouses are available Limit access of people, machinery, or utensils which have not been cleaned and disinfected Keep possible wild hosts and vegetable waste under control in the surroundings

In the case of viruses transmitted by aerial vectors (thrips, white fly, aphids), the most important, apart from what was mentioned above, is to prevent the access of these vectors into the greenhouse. It will thus be necessary to apply all the methods described to this end:    

Fit mesh to the side walls and roofs of the greenhouse with a maximum density of 20/10 cm2, except when this impedes adequate ventilation of the greenhouse. Fit a double greenhouse entrance gates or gate and mesh (minimum 20 x 10 strands per cm2) The greenhouse must maintain hermeticity so as to impede insect vector access Set yellow stickytraps for vector capture and follow-up

Furthermore it is necessary to 

Check soil and water quality

248

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

5.2 Curbing the spread of pathogens that have entered the greenhouse: To curb the spread of a pathogen inside the greehouse, the ideal scenario would be to have a set of the following measures in place, even if there were no trace of pathogen entrance. The initial outbreaks take time to detect and, if no preventive action is taken prior to their appearance, when their presence is detected it may be too late. 

 

Ensure adequate ventilation of all facilities because many pathogens require high relative humidity and/or water on plant surfaces as their optimum environmental conditions Thus, at colder and less sunny periods of the year early morning irrigation may be recommendable to allow the humidity to dry during the day Apply balanced irrigation to allow the seedlings to develop well without weakening the roots

To avoid the spread of pathogens transmitted by pathogens such as contact viruses (Tobamovirus, PepMV) or handling, such as bacteria and vascular fungi, or air-borne bacteria and fungi which are also transmitted by contact in the end:  

Work advancing in lines and always in the same direction in the greenhouse Disinfect, at least between lines, tools, gloves, etc. either with bleach or analogical disinfectants effective on any pathogen

In the case of vector-borne viruses: 

Control of the insect vector by the setting up of a good biological pest control system. The chemical pest control methods allowed are now practically ineffective in many cases

Whatever the disease, on appearance of the first outbreaks;  

Carry out a diagnosis which enables the precise identification of the agent causing the problem to know how to act At the end of the day, when work in the greenhouse has finished, the first plants to appear with symptoms must be pulled up and put directly into plastic bags for their disposal. These bags must be removed from the greenhouses without touching the healthy plants so as to avoid any new contamination. These plants must not be kept in the surroundings of the estates and must, therefore, be placed in the containers for controlled waste removal

249

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 



In the case of diseases caused by contact viruses or vascular bacteria such as Clavibacter michiganensis subsp. michiganensis, or Ralstonia solanacearum, even vascular fungi like Fusarium oxysporum, the elimination of plants that have come into contact with the diseased plant is also recommended, due to the fact that they may also be infected although they have as yet not shown any symptoms In these cases it is advisable to put the affected area into quarantine and work as little as possible in it and always at the very end of the day. The fact that plants infected for example by a virus, or the vascular bacteria and fungi previously mentioned, may not show any symptoms during part of the crop cycle could mean that these pathogens are very widely spread by the time the first case is detected, and that the control measures taken seem ineffective

In some cases, the use of chemical control is, probably, inevitable however there are many considerations to be taken into account regarding this. It is convenient to: 



Have a plan of action which contemplates the possibility of using preventive treatment against certain aggressive pathogens coinciding with the optimum for their development Obtain a positive identification of the causal agent of the problem to be able to apply the adequate chemical treatment and avoid the use of inefficient or unnecessary chemical formulae Be aware of pathogen resistance to said compounds, alternating between different types of products to avoid the development of resistances, etc. can be of great help

In any case, one way to avoid diseases is to use resistant varieties if they exist. 



Use resistant varieties. There are resistant or tolerant varieties for a wide range of pathogens. Resistances al ToMV in tomatoes, to PMMV in peppeto, al MNSV in melons, or to TSWV in peppers and tomatoes. Tolerance to TYLCV in tomatoes, to CYSDV in cucumbers, to CVYV in cucumbers, or to CMV in several crops. Resistance to Fusarium oxysporum, Verticillium, Podosphaera, etc., all of these are a good option for controlling these pathogens. It is important to bear in mind that there will always be races of pathogens and resistance to races. An alternative to resistances in many cases, above all when there aren’t any,is the use of resistant rootstocks as is the case with watermelons against Fusarium oxysporum f.sp. niveum. This option is effective against soil pathogens, of for example in the case PepMV to avoid the “collapse” syndrome.

5.3 Inter-season pathogen control: To eradicate a pathogen from a greenhouse between two seasons one must:

250

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria 

 



Clean the greenhouse well and remove all the vegetable waste from the whole estate. In the case of bacteria and vascular fungi, as well as for viruses transmitted by contact, remove as much as possible of the root system, especially the main root. Remove weeds and wild hosts, as well as spontaneous plants which can act as reservoirs for the next season Disinfect irrigation systems, structure, etc. with disinfectants and hot water. This is very important for the majority of soil and water-borne pathogens as well as contact viruses The disinfection of the soil or the substrate holders in hydroponic crops to be carried out will depend on the pathogen to be controlled ∙ ∙ ∙

∙



In the case of viral diseases transmitted by white fly or aphids it is not necessary to carry out any action in this media If it is a viral disease transmitted by white fly disinfection of the soil by solarisation may be a good way to control the pupa of these insects In the case of fungi and vascular bacteria, the solarisation of the soil is a necessary measure, in the case of fungi to reduce the inoculum and in the case of bacteria, to eliminate them In the case of PepMV solarisation in our climate conditions is totally effective if it is carried out in the summer (between June and August) and for a prolonged period and with the greenhouse completely devoid of vegetable waste including the main plant root In the case of contact virus belonging to the Tobamovirus group, solarisation will reduce the inoculum but it will not solve the problem. It is therefore recommendable to change crops or use varieties that are resistant to the virus you wish to control The more structurally complex greenhouses, with hydroponic crop systems, heating facilities etc. are more difficult to disinfect with solarisation. This is also the case with estates with more than one greenhouse where production takes place non-stop with the same crop. In these cases it is recommendable to lengthen the disinfection period and to consider the possibility of stopping production simultaneously in all greenhouses In the case of hydroponic crops, disinfection with solarisation of the substrate holders is more difficult, little effective on Tobamovirus or fungi like Fusarium and Olpidium, and possible with vascular bacteria and PepMV, although it is not 100 % guaranteed. This is the reason why it is a good idea to change the holders or look for other complementary alternatives such as the use of grafted rootstock, or resistant varieties and crop rotation. These can all be useful if one does not wish to change the containers

In cases in which there is no guarantee of soil disinfection and there is no alternative crop with resistant varieties, crop rotation is always an alternative. Be that as it may, crop rotation every so often is a recommendable practice to avoid soil exhaustion by pathogens

251

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria

References Alvarez, A., Barrera, C., Egea, R., Aguilar, M.I., Guirado, M.L., Serrano, Y., Gómez, J. 2002. Nuevas enfermedades causadas por hongos de suelo en los cultivos de tomate, pepino y judía del sudeste andaluz. En III Jornadas Nacionales de Semilleros Hortícolas. Ed. I.M. Cuadrado, M. Fernández, C. García. FIAPA, 2002. Almeria. Blancard, D. 2000. Enfermedades del Tomate. Observar, Identificar, Luchar. Ed. INRA y Mundi-Prensa. 212 pp. Blancard, D. Lecoq, H., Pitrat, M. 2000. Enfermedades de las cucurbitáceas. Observar, Identificar, Luchar. Ed. INRA y Mundi-Prensa. 212 pp. Davis, R.M., Subbarao, K.V., Naid, R.N., Kurtz, E.A. 2002. Plagas y enfermedades de la lechuga. Ed. Mundi-Prensa. Madrid. Díaz, J.R., García-Jiménez, J. Eds. 1994. Enfermedades de las Cucurbitáceas en España. Monografías de la Sociedad Española de Fitopatología n⁰ 1.Ed. Phytoma-España. 155 pp. Elorrieta, M.A. 20011-20012. Serie coleccionable “Principales enfermedades víricas de los cultivos hortícolas bajo plástico de Almeria” Almeria en Verde, n⁰ 90 a 99, pg. centrales. Elorrieta, M.A. 20012-20013.. Serie coleccionable “Principales enfermedades bacterianas y fúngicas de los cultivos hortícolas bajo plástico de Almeria” Almeria en Verde, n⁰ 101 a 109, pg. centrales. Elorrieta, M.A. 2005. Enfermedades bacterianas y fúngicas relevantes en semilleros hortícolas, pg 269290. En Dirección Técnica de Semilleros Hortícolas. Ed. Cuadrado-Gómez, I.M.; García-García, M.C.; Fernández-Fernández, M.M. Almeria, Spain. FIAPA. Elorrieta, M.A. 2006. Identificación de enfermedades fúngicas hortícolas en semillero. Vida Rural n⁰ 228. 18-22 Jones, j.B., Stall, R.E., Zitter, T.A. 2001. Plagas y enfermedades del tomate. Ed. Mundi-Prensa. Madrid. 74 pp. Jordá, C., Arias, M., Tello, J., del Moral, J. 1998. La sanidad del cultivo del tomate. Fisiopatías, plagas, enfermedades, malas hierbas, y su relación en el agrosistema. Ed. Phytoma-España. Valencia. 399 pp. López, M., García, J.P., Navas, J.A., Ortiz, F., Justicia, L., Fernández, M., López, J. 2001. Cultivos Hortícolas II. Plagas y enfermedades. Ed. Consejería de Agricultura y Pesca. Junta de Andalucía. 187 pp. Maroto, J.V., Gómez, A., Baixauli, C. 2000. La lechuga y la escarola. Ed. Caja Rural Valencia, Ediciones Mundi-Prensa. Madrid. Memoria de Actividades. 2004. Laboratorio de Sanidad Vegetal (Almeria). Consejería de Agricultura y Pesca. Junta de Andalucía. 87 pg. Messiaen, C.M., Blancard, D. Rouxel, F. Lafon, R. 1995. Enfermedades de las hortalizas. Ed. MundiPrensa. 576 pp. Namesny, A. 1996. Pimientos. Compendios de Horticultura 9. Ediciones de Horticultura S.L. Tarragona. 160 pp.

252

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Diseases affecting the main horticultural crops in the greenhouses of Almeria Reche, J. 1991. Enfermedades de hortalizas en invernaderos. Ed. Servicio de Extensión Agraria. MAPA. Madrid. 189 pp. Reche, J. 1994. Cultivo de la sandía en invernadero. Ed. Colegio Oficial de Ingenieros Técnicos Agrícolas de Almeria. 243 pp.

253

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Integrated pest and disease management in pepper crops Francisco Salvador Sola Nature Choice S.A.T.

Definition

Before we go into detail, it may be convenient to define what we understand by the integrated pest and disease management. It consists of combining adequately all the agrarian, physical, biological and chemical techniques available for keeping pests and diseases under control, and avoiding damage to crops, while at the same time reducing as far as possible the use of chemical pesticides. This general philosophy may be applied to any crop, from a field of cereal to a high-tech greenhouse, but -evidently- the focus has to be different. Upon approaching a plastic greenhouse pepper crop, the first step is to identify any problems and to have an in-depth knowledge of the life cycle for the causal agent of each of those problems. Later, preventive strategies must be designed to minimize the risk, and physical or cultural measures must be established to limit the Access or the development of the phytopathogens. The next step has to be the identification of beneficial insects, whether spontaneous or artificially released, which are present on the crop. Lastly, the use of phytosanitary chemicals must be considered, to cover any deficiencies in the integrated management system - pests or diseases for which there are no biological tools available, mismatches in the pest populations, phases in the crop cultivation cycle when it is not possible to establish beneficials … However, whatever the circumstances, the laid-down sequence must always be followed, prioritizing the other tools used over the deployment of chemical pesticides.

PREVENTION → BIOLOGICAL CONTROL → CHEMICAL CONTROL

In this presentation the laid-down order will be followed, concentrating on each of the practical problems, describing the life-cycle of the causal agent, the preventative measures which can be established, the available techniques of biological control and -finally- the chemical tools compatible with use here in Spain.

Identification of phytopathological problems in peppers

These can be arranged in three broad groups:

254

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops 



Main pests: This includes the pests which appear most frequently, and are normally the most destructive and - some of them - vectors for phytoviruses. Within this group we have the white tobacco fly (Bemisia tabaci), western flower thrips (Frankliniella occidentalis), various phytofagous mites (Tetranyckhus spp. y Polyphagotarsonemus latus), assorted species of leaf-stripping caterpillar, not to mention aphids Secondary pests: This group, classed plant-eating insects, tend not to appear on the crop when wide-spectrum chemical insecticides are used, but which start to thrive when treatments are reduced. If these populations explode, they can cause major damage to the crop, and for this reason it is necessary to identify them and keep them under control. Among the peppers of Almeria problems have cropped up with various stink bugs (Nezara viridula & Creontiades pallidus), some of the pseudococcidae (mealybugs, or Phenacoccus solani and Phenacoccus madeirensis), one fly (the pepper fruit fly, or Atherigona orientalis) and one of the cicadellidae (the leaf-hopper, or Empoasca spp.) Fungal diseases: Phytopathogenic fungi in peppers can cause serious damage to the crop. Setting aside ground fungi, the two main disorders are powdery mildew (Leveilulla taurica) and grey mould (Botrytis cinerea)

White tobacco fly (Bemisia tabaci)

The white tobacco fly has been one of the great pest infestations on a global level since the appearance, 25 years ago, of the famous Biotype B. Although we do not have any problems in the Mediterranean region with peppers infected by viruses transmitted by Bemisia tabaci, what is certain is that the insect breeds especially well on this crop, causing enormous damage. Its eggs are elongated and pallid, turning orange as they mature, and they are placed individually or in irregular groups, forming curved arcs. From these eggs emerges a small mobile stage (E1) which, after searching for a suitable place, attaches itself to the leaf and loses its mobility. After passing through three further stages of immaturity (E2, E3 & E4), an adult emerges, bearing the characteristics of the aleyrodid (white fly) family, easy to distinguish from other species because of its high-mounted wings, leaving on the leaf a transparent exuvia (abandoned outer skin) with a typically T-shaped exit. The immobility of these immature stages, and the habit of the adults to migrate towards the apical zones of the plant (i.e., near the apex) leads to a typical vertical distribution of the pest, separated into distinct layers on the plant, with adults, eggs and initial stages on the apices: advanced stages on the middle levels and abandoned outer skins on the lower. The duration of this life cycle depends on the temperature, and on the host plant consisting, in the case of peppers, of some 22 days at 25 ⁰C.

255

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 1: life cycle of Bemisia tabaci. a) Laying, b) Stage 1 mobile, c) Stage 2, d) and e) Varying degrees of stage 3 development, f) stage 4 also called pupa or nymph, g) and h) Adult-note the watershed arrangement of the wings typical to this species, i) Exuvio-note T-shaped eclosion hole

The preventive measures must be based on the hermetic seal of the greenhouses, a safeguard whose value is made complicated by the tiny size of the adult flies. The only way of achieving a full seal is the use of anti-insect meshes, as fine as possible. However, ventilation requirements make the use of meshes very difficult, especially those with sufficient density to stop the adult invaders getting through. It is considered that a mesh of aperture size 0.25 mm will impede the passage of most Bemisia tabaci adults. This is a gauge which only the meshes of the highest density ever reach -20 x 10 strands per cm2 (50 mesh)- which tend not to be used in commercial greenhouses. Given that it is impossible to stop adult flies getting through, the main preventive strategy is to capture them before they get to the crops, using yellowcoloured chromotropic (sticky) traps. However, the use of these traps has to be restricted in the early weeks, and most of them have to be withdrawn before the beneficial insects are released, because if not, most of the latter will be captured, too.

256

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 2: detailed view of agricultural meshes of different densities: a) 22x10, b) 20x10, c) and d) 16x10 8x10. In each image segment marked corresponds to 0.25 mm; single 20x10 mesh or higher density prevent the passage of adult Bemisia tabaci

Faced with the lack of physical or agricultural strategies to prevent the occurrence of this pest, there remains no alternative but to introduce as a preventive measure, the predatory mite Amblyseius swirskii, onto the crop. This phytoseiid has omnivorous tendencies, and can feed on pollen in the absence of pests, which is why very few are released when the first flowers appear. Introduction is usually undertaken by means of slow-release envelopes, which act like small individual bio-factories, allowing mites to escape onto the crops progressively, over several weeks. It should be borne in mind that A. swirskii preys only on the eggs and first stages of the bemisia tabaci: the more advanced nymphal stages can be controlled by various parasitic wasps, especially by the aphelinid Eretmocerus mundus. Given its tiny size, it is hard to see the adult wasps on the crop, but their presence can be detected by observing the nymphs and exuvia of the white fly, which display certain specific characteristics if they have been preyed upon by E. mundus. However, the action of these wasps is slow, and before they can assume control of the pest, a treacle-like deposit and black spots tend to appear on the crop leaves. When the leaves are covered by the sticky deposit, the Amblyseius swirskii cannot establish themselves properly, consequently, when the pests undergo a population explosion on them this acts as a source of infestation of the rest of the crop. It is fundamentally important that the release of the predatory mites takes place as early as possible, and when the population of white flies - especially the more advanced nymphal stages - is as low as possible.

257

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 3: life cycle of Amblyseius swirskii: a) Egg, b) Larva, c) Protonymph, d) Deutonymph, e) Adult, f) A group of adults and eggs on a pepper leaf

Figure 4: Eretmocerus mundus: a) Adult wasp on a pepper leaf, b) Stage 3 of B. tabaci parasitized by E. mundus mycetomas can be seen that are misaligned, due to parasite activity, c) E. mundus pupa close to hatching inside the cuticle of a juvenile B. tabaci, d) Exuvio, with a typical, circular eclosion hole, from which a wasp has emerged

258

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops The chemical battle against insects also comes into play. Before the release of the beneficials, we can use - remebering, of course, to keep the appropriate delay periods in mind - pyridaben as a contact adulticide, and pymetrozine as a systemic adulticide-lavicide. Both before and after the release of the beneficials - to correct imbalances -spiromesifen can be deployed and pyriproxyfen as ovicides, spirotetramat as a larvicide and potassium and phosphate soaps, according to the pH of the water, as adulticides. The active agents used must be selected to suit the population structure B. tabaci, as observed on the crop.

Western flower thrips (Frankliniella occidentalis)

Frankliniella occidentalis causes direct damage by feeding on the fruits, but its true importance as a pest is due to its role as a vector for the tospovirus TSWV (tomato spotted wilt virus), one of the most destructive phytosanitary problems known for pepper. This insect lays its eggs, encrusted in the vegetable tissue of the leaves or petals. From these emerges a larva which goes through two larval stages (L1 & L2) similar in shape and appearance but very different in size. When the second larval stage reaches its maximum development, it migrates to the soil, where it goes through two nymphal stages (N1 & N2) until it -after completing its transformation- emerges as an adult, and will now migrate to the upper part of the plant, to feed and reproduce. On peppers, this life cycle lasts an estimated 15 days at 25 ⁰C.

Figure 5: life cycle of Frankliniella occidentalis: a) Eggs, b) Larva 1, c) Larva 2, d) Pre-pupa, e) Pupa, f) Adult female, g) Adults on a pepper flower

Preventive measures based on a hermetic greenhouse seal are even more complicated with this pest. The entrance of Frankliniella occidentalis only be prevented with apertures smaller than 0.19 mm, and these can be obtained only in meshes of the greatest density, which result in an enormous reduction in ventilation. The capture of adults with blue chromotropic (sticky) traps is extremely effective, but has to be limited to the weeks prior to the release of the beneficials, because many Orius may also be trapped. Another important aspect to bear in

259

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops mind is the establishing of a long enough gap between crops, since the metamorphosis takes place in the soil (stages N1 & N2); if we do not leave at least 15 days without growing anything in the greenhouse, and/or set chromotropic traps, the recently-emerged adults will rapidly infest the young seedlings from the moment of planting, vastly complicating the integrated control of thrips.

Figure 6: detailed view of agricultural meshes of different densities: a) 22x10, b) 20x10, c) and d) 16x10 8x10. In each image segment is marked corresponding to 0.19 mm, none of which prevents the passing of adult F. occidentalis

The best, and most effective, control strategy is without doubt the use of the anthochoridae, or pirate bugs, Orius laviegatus, combined with the phytoseiid mite, Amblyseius swirskii, which -apart from controlling the white fly- exercises a complementary control over the first-stage larva of F. occidentalis. This bug can feed on pollen in the absence of the pest, which means -as with the A. swirskii- that it can, and must, be released once the first crop flowers have appeared. In this way, a population of predators will be consolidated which will eliminate the invading population of thrips before they become properly established on the crop. From this point of view, the best outcome is the earliest-possible flowering of the crop. What is more, the relationship between Orius laviegatus and the pollen is in no way secondary: the pollen is a vital element in the diet of the females during their development; otherwise their fertility, once they have reached the adult stage, will be extremely low. The maintenance of a population of Orius capable of controlling the thrips efficiently depends on keeping sufficient flowering going throughout the whole crop cycle, which is extremely difficult to achieve in winter, given the off-season cycles typical of Almeria.

260

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 7: Orius laviegatus: a) Egg, b) Nymph 1, c) Nymph 2, d) Nymph 3, e) Nymph 4, f) Nymph 5, g) Adult, h) Adults on a pepper flower

Chemical control of Frankliniella occidentalis is not very effective. It is even less so in Almeria, where the population of this insect displays high levels of resistance to all insecticides deployed. Further, the insecticides which are normally used against thrips are extremely toxic for the Orius and, in some cases, extremely residual. Without going further, the pyrethroids regularly deployed against the thysanoptera class of insect “acrinathrin or deltamethrin” wipe out the entire population of anthochoridae and impede the establishment of a new population by some 10 to 12 weeks (almost 90 days!): for this reason, it is impossible to use pyrethroids as part of integrated control, even in the nursery. Before the beneficials are deployed, we can use spinosad and lufenuron, the latter being effective only against larvae, but both active ingredients are highly toxic for the beneficials and caution must be exercised in respecting the timeline for their introduction. Against very early adult infestations of thrips, very typical when neighbouring crops are infected, chlorpyrifos or methyl-chlorpyrifos can be used for up to 15 days before the insects are released. In recent years there has been speculation about the larvicidal properties of spirotetramat, a product compatible with beneficials; this active agent causes a 40 % reduction in the A. swirskii, population, and therefore must be used with great care.

The spider mite (Tetranychus spp.)

Considered a minor pest among the peppers of Almeria (thanks to our particular growing cycle), this is without doubt one of the major problems in other farming areas. In the colonies

261

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops of this mite, we can find its spherical eggs, from which emerge its little larva (with three pairs of legs), which will go through the stages of protonymph and deutonymph, before reaching adult status. Before each ecdysis, the mites go into an immobile phase, during which they neither move nor feed. In the adults sexual dimorphism is clear and already observable in the deutonymph phase. Although it could appear frivolous, studying this mite’s development stages, in fact the structure and the mobility of the colony tell us much about its health, and help us to predict its future development and to take the appropriate steps to control it.

Figure 8: Tetranychus sp.: a1) Egg, a2) Larva, a3) Protonymph, b) Deutonymph, c1) Adult male, c2) Young adult female, d) Mature adult female

The preventive measures against Tetranychus have to be taken before the planting of the crop, and they are absolutely vital if the farm has suffered attacks in the past. The elimination of weeds before the crop is planted is very important, both in the greenhouse and its surroundings, with special attention being paid to plant species which are very attractive to this mite pest. Such plants include the convolvulus (Convolvulus arvensis) and the mallow (Malva parviflora). Dusting with sulphur is very effective (a dosage of 50kg per hectare) prior to planting. Biological control is based on the phytoseiid Phytoseiulus persimilis, a specific predator of the Tetranychus species. As it is specific, it cannot be used as a preventive measure: control requires the location, as early as possible, of the colonies of the spider mite, which should be marked for the release of beneficials at this exact point. It is a process which needs continual work and close attention on the part of all the staff on the estate. Fortunately, if the

262

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops Tetranychus pressure is not extremely high, A. swirskii is capable of effectively controlling the pest on peppers, preventing the formation of large colonies. In other agricultural areas, where this pest pressure is greater, the phytoseiid Amblyseius californicus is used.

Figure 9: Phytoseiulus persimili: a) Egg, b) Larva, c) Protonymph, d) Deutonymph, e) and f) Adults

In fact, the chemical control of this pest is very straightforward, given the efficacy of spiromesifen, although there are also other active ingredients which are very effective against the spider mite, and compatible with the beneficials used against other pests. It must be borne in mind that the use of spiromesifen is incompatible with Phytoseiulus persimilis, because this active ingredient is extremely toxic for this predator.

The broad mite (Polyphagotarsonemus latus)

It is a tiny microscopic mite -less than 0.2 mm in size- which causes deformations in the growing tips of the plant. Its morphology cannot be seen at a casual glance. These mites can hardly be distinguished when using a magnifying glass, and require a stereoscopic microscope for their positive identification. However, in the field, the symptoms of their presence are sufficiently clear for those with sufficient experience to be able to identify the problem.

263

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 10: Polyphagotarsonemus latus: a) Egg, b) Larva, c) False pupa, d) Adult male, e) Male charging the female false pupa, f) Adult female

Prevention of this mite is complicated, and in reality all that can be done is to come close to controlling its dispersal mechanism, which is nothing more than phoresis (transmission). The white spider enters the crop and disperses by clinging to the extremities of other insects, which act as its vector. This method of phoresis has also been observed in white flies and thrips. The best means of controlling P. latus is to tackle it as early as possible. Furthermore, there are grounds for suspecting that Bombus terrestris (bumblebee) is also capable of spreading this mite, and for this reason natural pollination should be suspended if colonies of broad mites are detected on the crop. Although there is evidence that A. swirskii preys on this mite, control aimed at its established focal points is not sufficiently effective. Early detection of these focal points, and localized powdered sulphur treatment, are the best methods for controlling the pest. However, if it succeeds in dispersing, then we have to rely on espiromesifeno.

Defoliating caterpillars

Various distinct species of leaf-stripping caterpillars appear on the pepper crops of Almeria. These can damage the crop, or even, far more seriously, disrupt the harvest. It is the noctuidae family which provides most of the pests: Spodoptera exigua is without doubt the most frequently-occurring and problematic, but there are other noctuidae such as Spodoptera litoralis, Helicoverpa armigera and Chrysodeisis chalcites. There again, damage caused by

264

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops Platynota stultana -a tortrix moth- is increasingly common, though so far no significant attacks have been reported.

Figure 11: Spodoptera exigua: a) Laying. b) Larva 1. c) Larva 2. d) Larva 3. e) Larva 4. f) Larva 5. g) Pupa. h) Adults. i) Damage to pepper crop

Prevention of these lepidopterae has come on a lot in recent years, thanks to improvements in sexual confusion techniques, using pheromones. These techniques are founded on the release into the surroundings of vast quantities of one of the sexual pheromones specific to this pest. The massive presence of the molecule diffuses the scent trail of the female, making it difficult for the male to find his mate, and therefore impeding reproduction. Release onto the market of sexual confusion techniques enables the total control of Spodoptera exigua populations, and interferes quite efficiently with Spodoptera litoralis and Chrysodeisis chalcites. However, it does not affect other species, which have to be monitored and controlled by other means. Although a great number of predators and parasites exist for these leaf-stripping caterpillars, up to the present it has not proved possible to find a single one capable of exercising control in the field. However, we now have a good combination of chemical and biological weapons for combating these caterpillars. After the release of the beneficials, we have on the one had two biological tools: Bacillus thuringiensis and the nuclear polyhedrosis virus of Spodoptera exigua (VPNSp). On the other hand, there is a variety of active ingredients with different modes of operation: Ca channel blockers; chlorantraniliprole and flubendiamide, accelerators of the

265

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops molting process; tebufenozide 1and methoxyfenozide and Na channel blockers; indoxacarb2. Furthermore, before the release of the beneficial insects (respecting the release timetable), other “families” of insecticide can be used against the caterpillars. C1 channel activators; emamectin, Acetylcholine receptor blockers; spinosad or Chitin formation inhibitors; lufenuron. It is absolutely essential to alternate these tools so that, in the process of controlling the pest, we avoid the creation of populations which are resistant to the main insecticide “families”. In this sense, intensive use of the diamides; chlorantraniliprole and flubendiamide, in recent seasons is a very worrying tendency.

Aphids

Practically little more than anecdotal during the chemical control years, the arrival of integrated control has restored the critical importance that this pest enjoys in other agricultural zones. Peppers in Almeria tend to be host to two species of aphid; Myzus persicae and Aphis gossypii, easily distinguishable in the field by observing their “syphons” (the same color as the body in the case of Myzus persicae, or completely black for Aphis gossypii). Less frequently, other species can be found, such as Aphis craccivora, Macrosiphum euphorbiae and Aulacorthum solani.

Figure 12: Species of aphids on pepper crops in Almeria: a) Myzus persicae. b) Aphis gossypii. c) Aphis craccivora. d) Macrosiphum euforbiae. e) Aulacorthum solani

The preventive technique par excellence in the control of aphids is based on biological control and is none other than the use of the “banker plant”. It consists of sowing in the greenhouse

tebufenozide is active against Spodoptera exigua only Indoxacarb affects somewhat less than half of the Orius laviegatus nymphs, and for this reason is considered “category 2”. To protect against Orius you need only apply it on crops with a well-established population of bugs, consisting mainly of adults. 2

266

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops (at the same time as the crop) cereal plants (usually oats) in a quantity sufficient to establish a species of aphid specific to the grass, usually Rhopalosiphum padi, which will contribute to establishing a population of the pest aphid’s main parasite, the brachonite Aphidius colemani, within the greenhouse. All of this is done before the pest appears on the crop. A community of predators will be established around these cereal plants (coccinellidae, ziphiidae, cecydomyiidae, lacewings) which will assist enormously in controlling the aphid pest, above all in the phases when Aphidius is itself least effective.

Figure 13: Aphidius colemani on cereal reservoir plants: a) Female of A. colemani parasitizing an aphid. b) Larva of A. colemani inside an aphid. c) Larva of A. colemani weaving its cocoon inside an aphid before pupation. d) A. colemani mummies . e) Oatmeal plants with cereal aphid (Rhopalosiphum padi) f) Adult of Aphidivorus sirphophagus hyperparasite. g) Adult Dendrocerus sp. hyperparasite. h) Adult Pachyneuron sp. hyperparasite i1) A. colemani mummy with circular opening. i2) Mummy with an irregular eclosion hole of a hyperparasite. j) and k) Sirphid Eupleodes collorae adult and larva. l) Adult coccinellid. m) Aphidoletes aphidimiza larva. n) and o) Scymnus sp. adult and larva

The Aphidius colemani, the principal beneficial in biological control of aphids, has certain limitations. Wasp larvae, which grow in the aphid’s gut, are sensitive to the higher summer temperatures of the greenhouse. What is more, in the wild there is a series of wasp species which feed parasitically on Aphidius larvae, and which in turn are parasitic on the aphid itself

267

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops and are generically known as “hyperparasites”. These two factors mean that from late spring until autumn arrives, biological control of aphids cannot take place using parasitoids only. The maintenance of aphids in low populations, most of all Aphis gossypii, has taken on special importance in the face of the recent detection of PeVYV3 - Pepper Vein Yellows Virus - in Almeria. It is a polerovirus transmitted by several species of aphid, but particularly efficiently by this species. A persistent circulative transmission virus, PeVYV arrives on the crop via winged females who have acquired a lifelong infection after developing on infected plants. However, there are still many questions which need answering about the true importance of this virus and the influence of ambient conditions on its virulence, and the seriousness of its symptoms. The fact that we have to keep the aphid population as low as possible should not lead us to lose perspective. For peppers, there are three insecticides compatible with beneficial insects, which keep other pests under control, while attacking the aphid: Pirimicarb, pymetrozine and spirotetramat. Pirimicarb is not effective against Aphis gossypii, and both pymetrozine and spirotetramat work by ingestion, and because the aphid must feed on the plant, it will ingest them and die. Therefore, the use of these insecticides does not guarantee the absence of the virus from the crop. Only a “cocktail” of all these aphid control strategies can ensure adequate control of PeVYV.

Secondary pests

We understand “secondary” pests to be those which tend not to appear during chemical control, owing to the effects of insecticides deployed for other species, but under integrated control (thanks to the reduced treatments) they appear, and even thrive, on pepper crops. If the populations of these insects are not detected and controlled in time, the damage which they cause can reach serious levels, and for this reason their early detection in the field is of fundamental importance. Agricultural labourers have a decisive role to play here. Next, it is vital to know the appropriate measures of prevention and control.

9.1 Pseudococcidae (Phenacoccus solani & Phenacoccus madeirensis) Two years after the massive implementation of integrated pest management in the estates of Almeria, problems emerged with mealy bugs. The most serious is, without doubt, Phenacoccus solani, a species which is parthenogenic (without males) and viviparous (eggless, giving birth to live young). It infested the autumn crops, and its presence in the greenhouses was eventually massive, with very serious infestations in some places. The following year, colonies of another species began to appear on pepper crops of the spring cycle - this time it was Phenaoccus

In recent months, the accepted nomenclature of this virus has been the subject of debate. Very similar symptoms have been associated with different viruses in other countries. Thus in Japan, they talk of PeVYV, and of PYLCV – pepper yellow leaf curl virus – in Israel. In Turkey, it is PYV – pepper yellow virus. Recent genetic studies have demonstrated that all the isolated strains are closely related, accepting that they are local outcroppings of the same virus, which has now been given the definitive name of pepper vein yellows virus.

268

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops madeirensis, a species which can adjust to a typical cycle (with males and eggs), although on this occasion the problems were not as serious.

Figure 14: Pseudococcidae in greenhouse: a) Colony Phenacoccus solani. b) P. solani adult female. c) Leptomastix algiricaa dult, parasitoid of P. solani. d) Damage to pepper by P. solani. e) Phenacoccus madeirensis colony. f) P. madeirensis adult female producing an ovisac. g) P. madeirensis adult male alongside several male pupae cocoons. h) P. madeirensis damage to peppers

Pseudococcidae are a group of insects with a complex biological life pattern. Their control by parasites is very slow; their appearance in large numbers very costly and the identification of the species which are pests - necessary if the right parasite is to be chosen - is very difficult with the means available in the field. Predators are generalized, but in the one unique case of a commercially-available specific predator (Criptolaemus montrouzieri), the bug does not adapt well to greenhouse conditions. Notwithstanding this, the spontaneous appearance on the Phenacoccus solani of the encyrtidae Leptomastix algirica4 triggered the release onto the market of this “new” parasite, with varying results.

There is an enormous controversy over this species, between entomologists of Western and Eastern Europe. The Westerners, led by the British, consider it an obscure variant of Leptomastix epona, while the Easterners, under the aegis of the Israelis, regard it as a completely separate species.

269

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops Although it was not effective when it appeared during the era of chemical control, the appearance in the marketplace of spirotetramat, extremely efficient when used against these insects, has led today to the disappearance of this pest problem.

9.2 Ants (Tapinoma nigerrimun) The reduction of chemical treatments in the greenhouses had made it possible for various ant species to occupy the agro-ecosystem. Most of these species are solitary hunter-foragers, and do not interfere with pest control, but Tapinoma nigerrimun, a polygynous species with great diversity of habits, can cause problems. Apart from its direct predation on auxiliary insects, principally the nymphs of Orius, this species “farms” the colonies of homoptera (aphids, woodlice, and white fly), rendering their control very difficult. There are currently no preventive or biological techniques to deny these ants access to the plants. Neither do we have chemical insecticides which enable the elimination of the ants, while at the same time preserving the beneficial insects. The only tool available for controlling Tapinoma nigerimum is to use chlorpyrifos as bait, deployed in the soil. Its use will not eliminate the ants, but it will slow down its progress and will eventually force the ants to look for alternative food sources.

9.3 Stink bug (Nezara viridula) This is an insect of the pentatomidae genus, of great size, nearly two centimeters in length which causes feeding damage to fruits so severe as to make them completely worthless. In the very early autumn growing season, and also in spring, it is considered a major pest, capable of causing production losses on a grand scale. Nezara viridula lays its eggs in honeycomb patterns and, after hatching, the young, with black and white patterning, go through three early nymphal stages (N1, N2 & N3). During these early stages, the nymphae display gregarious behaviour, remaining together in groups and eating the same fruit. In the two following nymphal stages (N4 & N5), the colour green predominates, and individuals begin to disperse into the surroundings. From the final moult the adults emerge, with a marked sexual dimorphism in size. After copulation, the insects’ life cycle closes (about fifty days). All stages of the insect excrete a foul-smelling liquid if disturbed. This acts as a defence mechanism against predators.

270

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 15: Nezara viridula: a) Laying. b) Hatched eggs. c) Nymph 1. d) Nymph 2. e) Nymph 3. f) Nymph 4. g) Nymph 5. h) Nymph 6. i) Copula. j) Feeding damage to pepper fruit

Although there are known parasites of both the eggs and the adult Nezara viridula, the effectiveness in the field of these is too low to prevent crop damage. For this pest, integrated control has to be based on prevention, carefully maintaining the hermetic seal of the greenhouses - which shouldn’t be so difficult with an insect so large - and watching vigilantly for the appearance of concentrations on the crop. If the stink bugs are detected in their early stages, when they are still gregarious, it is easy to control them with localized applications of lambda-cyalothrin. If the pest spreads throughout the greenhouse, it will not be possible to use this active ingredient, which is extremely toxic for both Orius and A. swirskii; the only

271

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops alternative is tiametoxam5 which, although poisonous for the antochoridae, at least does not affect the population of predatory mites.

9.4 Boll shedder bug (Creontiades pallidus) This miridae bug, traditional pest of the Spanish cotton fields, causes problems in all peppergrowing areas in the Mediterranean Basin which use biological control. Since Almeria changed to integrated control in 2007, the intensity of this pest has been on the increase, to the point where it has become the major pepper pest in recent years. The bugs eat the immature fruits, producing small russeted patches on the fruit wall which, as the fruit swells, show as dark discolorations, sometimes surrounded by green-coloured “halos”. The problem is especially acute in the pepper varieties which turn yellow on ripening.

Figure 16: Creontiades pallidu. a) Nymph 1. b) Nymph 2. c) Nymph 3. d) Nymph 4. e) Nymph 5. f) Adult. g) Feeding damage to pepper fruit

Creontiades pallidus buries its eggs in the plant tissue, so they are extremely difficult to locate. Small nymphae emerge from these with legs and antennae which are long and striated. They

The European Union recently has authorized the precautionary suspension of tiametoxam, along with other neonicotinoides, for certain crops among which, for now, peppers are not included. It is to be expected that the legal position of this active ingredient will undergo changes over the coming months. In any case the deployment of tiametoxam should always be on the leaves, because if it is applied through watering, residue can be left behind which will impede the normal establishment of Orius laviegatus in the following crop.

272

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops go through five nymphal stages (N1 to N5). After the final moult, they emerge as typical miridae adults, with long antennae and a colour between green and brown, and they measure approximately a centimetre in length. Their cycle is complete in roughly 21 days. Preventive management of Creontiades pallidus must be based on the control of white fly, because it is the large populations of the latter which attract the boll shedder bug to our greenhouses. Just like many other miridae, this insect is an optional plant-eater which prefers to feed off other insects (mainly white fly), but which will eat vegetable material when reserves are exhausted. If we have a large population of Bemisia tabaci at the start of the growing season, the boll shedder bugs will come into the greenhouse to feed on them and, when beneficial insect activity has decimated the aleyrodidae, they cause damage to the crops. From this point of view, measures such as hermetically sealing greenhouse vents, anti-white fly chemical treatments prior to the deployment of beneficials and the earliest possible release of A. swirskii, coinciding with the first flowers, are fundamental for proper control of this miridae. If eventually the Creontiades pallidus population reaches high levels, it can be reduced by means of an application of indoxacarb and azadiractina, mixed, but it is not wise to abuse these applications through over-use, because they can also reduce the Orius laviegatus population.

9.5 Lesser pepper fruit fly (Atherigona orientalis) Although it cannot be said that this diptera is, strictly speaking, a pest, it proliferates around crops associated with the presence of other pests and diseases and can causes significant losses among pepper crops. This fact, together with the paucity of control techniques beyond extensive trapping with chromotropic sticky pads, forces us to get to know this insect, and to avoid crop conditions which can lead to these problems. Atherigona orientalis is a typical saprophytic fly which abounds on decomposing vegetable material. Like any insect which passes its entire life cycle in this type of material, the adults carry saprophytic microorganisms on their legs -such as Pectobacterium carotovurm-. In conditions which favour rapid decomposition of fruit (heavy worm attacks on the fruit, unhygienic conditions among the crops or their surroundings) the population of A. orientalis will explode in the presence of the bacteria. If we also have a significant Creontiades pallidus population, the feeding lesions caused in the fruit by the bugs will be taken advantage of by the flies for laying their eggs, infecting the lesions with bacteria as they do so. The result will be a heavy attack of bacteriosis in the crop, which will not be amenable to control by bactericides until the A. orientalis population, which is acting as its vector, is brought to heel.

273

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 17: Atherigona orinetalis: a) Adult on a pepper flower. b) Adult. c) Eggs. d) Larva. e) Larvae in rotten fruit. f) Pupae in the dry remains of a rotten fruit

The adults of this diptera are typical flies, with a brown color and very active and elusive (in the field, very difficult to distinguish from other flies), which tend to lay their eggs in the calyx of the fruit. From the eggs emerge whitish larvae which pass the entire larva stage eating decomposing fruit, swimming without any trouble in the bacterial liquor. Having completed their development, they form pupas in putrefying vegetable waste, from which they emerge as adults. Being saprophytes, they can spend their entire life cycle in fruit, even though this has been separated from the plant and removed from the greenhouse. The adults return to the greenhouse once they have completed their metamorphosis. The best control method is to maintain the crop in conditions of extreme hygiene, removing all vegetable waste and immediately removing the remnants of pruning. The area around the greenhouse should be cleared, and all waste kept in lidded containers.

9.6 Green mosquito (Empoasa spp.) This is a cicadellidae -very much at home on vines, citrus and other fruit trees- which has for several years been causing serious problems in the Campo de Cartagena (Murcia), and which, just last season, appeared in the greenhouses of the Campo de Dalias (Almeria), causing eating damage to leaves and fruits. On the leaf, this damage appears as erosions which bring to mind the depredations of the spider mite, while on the fruit they appear as lines of little, sickly green puncture marks which render the fruit completely worthless.

274

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 18: Empoasca sp.: A) Adult. b) Nymph. c) Pepper fruit damage. d) Damage to pepper leaf

The adults are small cicadellidae, green in colour, very active and nervous, which camouflage themselves very successfully among the crops, flying away when disturbed. The nymphae resemble the adults closely except, of course, for their lack of wings and are every bit as good at camouflage, clinging to the underside of the pepper leaves. With regard to controlling them, if they are detected early they are very easy to deal with, by means of summer oil applications, but when their populations are high, we must resort to a mixture of indoxacarb + azadiractina in order to control them. Mass trapping with yellow chromotropic sticky pads has produced excellent results with large infestations impossible to control chemically, at the cost of losing a percentage of Orius laviegatus.

10 Powdery mildew disease (Leveilulla taurica) Leveilulla taurica is without doubt one of the most destructive diseases known to pepper cultivation and, up to now, has proved to be the most important and frequently-occurring problem among pepper crops subject to integrated control. The disease appears in autumn and spring, coinciding with the plant’s most active periods, and manifests itself as yellowish stains on the leaf face and exhibits a characteristic white “felt” on the leaf’s underside.

275

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 19: Leveilulla taurica: a) Severe attack on a pepper crop. b) to f) Infective process: b) Asexual spore (conidium) wound on the leaf. c) The conidia germinate when conditions are optimum, form an appressorium through which they flow through the plant cuticle. d) Once inside the leaf it sends out haustoria to feed off the cells without killing the plant. e) The mycelium completely invades the intercellular spaces, forming haustoria on all cells; feeding fungus eventually kills plant cells, which take on a yellow color. f) The mycelium comes out through the stomata and forms conidiophores, which form new conidia.

276

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops In order to concentrate our integrated management on this fungus, we need to know its life cycle. This starts when an asexual spore (known as a “verum”) lands on the face of a leaf. If conditions of light, temperature and humidity are adequate, this verum will germinate, sending out an initial mycelium, which will rapidly form an appressorium and a hypha for penetration, which will pass through the plant’s cuticle, launching the infection. This initial mycelium grows, occupying the intercellular space -the apoplast- and sending out haustoria, or roots, structures which break through the walls of plant cells without killing them. The fungus feeds off the pepper plant by means of these haustoria, continuing to grow and sending out new haustoria, until the mycelium occupies the entire symplast and all the parenchyma cells are subject to parasitic attack. As a result of the fungus’ feeding, the parenchyma of the leaf starts to collapse. It yellows, a symptom which is obvious at a glance. At this point, the fungus emerges from the stomata on the leaf’s underside, sending out an external mycelium and conidiophores, which develop new conidia, the whitish “felt” visible to the naked eye. From the germination of the spore to the development of the conidiophores a period of 20 days is necessary, which means that if we are to prevent the disease, we will need to take measures three weeks before the appearance of the first symptoms. Any preventive strategy directed against Leveilulla taurica must base itself on sulphur, which is the only fungicide with a preventive effect on this fungus. The fungicidal action of sulphur is based on its sublimation, the process by which solid sulphur passes directly to a gaseous condition, and which occurs spontaneously at temperatures above 18 ⁰C. The molecules of gaseous sulphur (S8) form a ring of eight atoms which is soluble in ergosterol, the main component in the cellular membrane of true fungi. Thus, it can penetrate the interior of the conidia and the initial mycelia of Leveilulla taurica, altering their metabolic processes and causing the death of the fungus before it can complete its infestation. Because of the nature of its action, it is not necessary to apply sulphur directly onto the plant in order to get effective results: we can secure a successful outcome merely by adding it to the soil of the greenhouse, whether in shovelfuls, or by means of an adapted pulverizer, always at temperatures above 18 ⁰C. With lower temperatures, sulphur vaporizers have to be used, devices with an electrical resistance which heats up the sulphur, causing its sublimation: but this equipment requires electrical installations spread throughout the greenhouse, and their deployment is therefore more complicated. If, eventually, infection occurs, we must resort to systemic fungicides, since sulphur is not effective against the internal mycelia of this fungus. Although it would appear at first glance that there is a plethora of fungicides on the market which will combat oidiopsis, a deeper analysis of their modus operandi reveals the truth. All of the anti-powdery mildew fungicides belong to three groups: QoI6 fungicides (the strobilurins), integrated with azoxystrobin and methyl kresoxim; the hydroxypyrimidines, whose only representative is bupirimate, and the large group of DMI7 fungicides (triazoles and related types), into which all of the other antioidiopsis products are grouped (flutriafol, triadimenol, penconazole, myclobutanil and

6 7

Quinone Outside Inhibitors DeMetilation Inibitors

277

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops ciproconazol). For good control of powdery mildew, and for proper management of resistance, it will be necessary to alternate treatments, using products with different modes of action.

11 Grey mould (Botrytis cinerea) If powdery mildew is the most frequently-occurring disease among peppers during spring and autumn, grey mould (caused by Botrytis cinerea) is unquestionably the gravest phytosanitary problem of the winter months. This fungus gets absolutely everywhere, and can be found in every corner of the greenhouse, usually acting as a saprophyte. However, if the conditions are adequate (humidity close to saturation point and large differences in temperature between day and night) the spores will germinate and the mycelium will invade plant tissue. Once the mycelium has penetrated the plant’s skin, it will secrete enzymes which destroy the structures supporting the cells, which will eventually collapse and allow their contents to escape. This is how the mycelium of the fungus thrives, rapidly emitting conidiophores which in turn form new conidia, giving the lesion the appearance of greyish felt which is familiar to all of us. Under certain conditions the fungus can form very resilient structures of resistance known as “sclerotia”, but it can also survive directly, in the form of mycelia, on vegetable waste or even in the soil. Despite its apparent simplicity, Botrytis cinerea is a very complex fungus whose biology, notwithstanding numerous scientific studies, is still not fully understood. However, we do know that certain agricultural conditions favour attacks by this fungus, and therefore they have to be avoided as much as possible. It is known that excess nitrogen in the plant tissue favours germination of the conidia and the growth of the mycelium and it follows that overuse of nitrate fertilizers, and products based on amino acids, must be prevented during periods of high risk. Moisture conditions in the soil are very important, because excessive watering of the crops facilitates the penetration of the hyphae, it is necessary to adjust irrigation volume, frequency and timetable in order to avoid this. This will also lead to a reduction in the greenhouse’s relative humidity. The moisture level inside the plant is a point of critical importance. The conidia of Botrytis cinerea need a relative humidity close to saturation (greater than 90 %), and new spores can form only when humidity exceeds 75 %. It is therefore fundamental to try to avoid conditions of high humidity in the greenhouse, and in proper ventilation management is a key tool. The fitting of double roofs, which allow ventilation and prevent rain water falling directly onto the crops, is a great help in this regard.

278

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops

Figure 20: Botrytis cinerea: a) to f) Infection process: a) The spore fixes itself to the plant surface without the need for high levels of humidity. b) Although there are strains capable of directly traversing the cuticle of some species, the presence of a wound is usually required for infection to take place. c) The conidia germinate only when relative humidity reaches saturation point, which involves the condensation of water on the plant, the initial mycelium penetrates the wound and starts infection. d) The mycelium emits various enzymes which destroy the cellular structure of the vegetable, the cells collapse and release their contents, which the fungus feeds off. e) The mycelium develops and the infection progresses. f) Conidiophores are produced which in turn give rise to conidia-forming new felt-like grey substance observed in crops. g) Fruit damage to fruit. h) Stem damage.

However, these measures do not guarantee that we will avoid infection. Thus, if it begins and the greenhouse air is loaded with Botrytis cinerea conidia, it will be necessary to take extreme precautions in order to minimize losses as much as possible, putting in place a series of measures to slow down the onset of the disease. Getting rid of dry, spent flowers and other small-scale vegetable waste will eliminate potential infection hot spots and help to keep the crops dry. There must be no work on the crops on rainy days, because the slightest nick of any kind will cause small lesions which serve as entry-points for the fungus. The removal of

279

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops damaged plants must be carried out with consummate care, avoiding any throwing of waste onto the soil, and striving to disperse spores as little as possible. When fruit is gathered, the stalk should be cut at its base, where it connects with the plant stem, which is the point where scar tissue forms quickest and best, leading to the cleanest possible cut. It is advisable to use a sharp knife, rather than scissors and taking care not to damage the main stem. A highly recommendable practice is the use of a home-made disinfectant solution (peroxide or sodium hypochlorite) to clean cutting tools during work. This will contribute to the cleaning and scarring of the harvest cut.

Figure 21: Measures to limit the spread of Botrytis cinerea in crops: a) Double roof vents to allow ventilation and prevent dripping. b) Avoid massive plant waste clearance which may disperse the fungal conidia. c) The cut at the base of the stem to facilitate healing; note the centred position of the vascular bundles in the photo highlighted in green. d) Make clean harvesting cuts. 1e) to e4) Avoid twisting the blade while cutting as it causes damage to the stem in an area where healing is difficult

With regard to chemical control, there is currently a wide spectrum of fungicidal products which combat Botrytis cinérea acting from different points. There are hydroxyanilines such as fenhexamid, dicarboximides like iprodiona, an anilinopyrimidine such as pyrimethanil and a DMI fungicide like tebuconazole, to which a mixture of anilinopyrimidine, ciprodinil, with a phenylpyrrole, fludioxonil can be added. However, we should not forget that Botrytis cinerea is a fungus with a surprising ability to generate resistance to fungicides. The proper use of fungicides requires us to alternate products with different procedures, using them only when

280

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Integrated pest and disease management in pepper crops the initial symptoms of the disease are detected. For preventive treatment during periods of risk, it is preferable to use contact fungicides which have multi-site action capability, such as clorotalonil.

281

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops

The integrated pest and disease management of tomato crops David Erik Meca Abad Cajamar Research Centre ‘Las Palmerillas’

Introduction

Agriculture’s main mission is to produce food. However, that production is under threat from organisms competing with the crops, especially pests, diseases and crop invasions by weeds, as well as adverse weather phenomena. All these severely limit food production and cause substantial financial losses At the G20 States Agriculture Ministers’ meeting in Paris, in 2011 it was recommended that measures be taken to increase agricultural productivity and food production and to guarantee the mid and long term sustainability of the global agri-food system. This context requires the use of phytosanitary products which are compatible with people’s health and with the environment: The objective is to produce food in a sustainable way from a social and environmental point of view.

The EU has taken measures to that effect, amongst which is the 2009/128/CE Directive on The Sustainable use of Pesticides, which encourages a series of key actions:

  

Plans for the reduction in the use of phytosanitary products, amongst which Integrated Pest Management (IPM) takes pride of place Precautions for protecting the aquatic environment, drinking water, public spaces and areas which have been awarded environmental protection A compulsory training system for all users to avoid the inadequate use of phytosanitary products and the correct use of application equipment

Integrated Pest Management is a global production management system in which decision taking is based on duly justified technical criteria. In the context, pest and disease control is carried out in combination, and/or in a way which is compatible, with chemical and biological control and various cultural techniques aimed at reducing risks both to people and the environment.

282

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops

Most common tomato crop diseases

2.1 Mites Spider mites: Tetranychus urticae Koch, tetranychus turkestani Ugarov and Nikoski, tetranychus evansi Baker and Tetranychus ludeni Zacher. These species are usually native species and are very well adapted to our weather conditions. They feed off and reproduce on a large number of different vegetable species. Thus, their populations in agricultural areas are both very dynamic and unstable. They reproduce actively throughout the year, dispersing from plant to plant and rapidly establishing densely populated colonies. The external appearance of the four species is similar. The colouring depends on age; from the colourless to very light tones of the youngsters to the varying shades of red of the adults. The damage they cause is similar, diffuse discolouring which are, in fact small whitish patches on the leaves where the epidermic cells have been sucked out and the silk which covers the colonies. It attacks the underside of the leaf, mainly. The invasion begins in a series of locations; if the number of mites is too high they will migrate to the apical area of the leaves where they produce large amounts of silk to enable them to disperse. Preventive Control    



Disinfection of structures, floor and soil prior to planting in plots with a record of spider mites Removal of weeds and greenhouse vegetable waste Avoid excess of nitrogen Observation of crops during the first phases of development, especially the areas closest to the gates, sidewalls or sides of the greenhouse as they are the main entrance points Early detection of the sources due to the fact that they are easier to control that way

Biological Control The main predatory species of spider mite eggs, larvae and adults are: Amblyseius californicus, Phytoseiulus persimilis (native and purpose-bred species), Feltiella acarisuga (native species). Chemical Control Abamectin, Paraffin oil, azadirachtin, sulphur, clofentezin, etoxazol 11 %, fenbutatin fenpyroximate, flufenoxuron, oxamyl, pyridaben, spiromesifen and tebufenpyrad.

283

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops

2.2 Tomato russet mite: Aculops lycopersici (Massee). The well known tomato russet mite is present all over the world. It is very polyphagous, free living (it does not live protected in gills) and it tolerates low levels of relative humidity causing greatest damage and developing the most at high temperatures and low humidity (spring and summer). Damage starts at the lower part of the plant, the lower leaves curl and become silvery. The stem becomes characteristically bronzed and long cracks begin to appear in it. If the damage continues the leaves dry and fall and fruit production is affected with dark brown scabs and cracks starting at the calyx. Preventive Control   

Disinfection of clothes, footwear, tools Removal of seriously affected plants Care must be taken when handling the crops because the virus is easily transmitted during pruning, thinning, etc.

Biological Control Experiments with predatory mites, Amblysieus andersoni, are being carried out. Chemical Control Abamectin, paraffin oil, azadirachtin, sulphur, oxamyl, spiromesifen.

2.3 White fly White fly is the name given to a group of around 1.556 different species of insects. Regarding horticultural plants grown under plastic in Spain there are two species of white fly which cause a serious problem in greenhouses; Bemisia tabaci (Gennadius), also known as the cotton white fly and Trialeurodes vaporariorum (Westwood) or greenhouse whitefly. Both species are currently considered to be harmful to tomato crops in the Mediterranean Basin, Trialeurodes being more prevalent in milder areas and Bemisia in warmer areas It is an aggressive and polyphagous pest which causes serious damage to crops. It owes its name to the fine layer of wax which covers the adults’ bodies. The young areas of the plant are colonized by the adults which lay their eggs on the undersides of the leaves. The larvae, which are mobile, emerge from these. After attaching themselves to the plant they go through three larval, and one pupa, stages the last being characteristic for each species. Generally speaking, the damage caused by white fly comes under two categories: direct damage (yellowing and plant weakening) caused by the larvae and adults when feeding, sucking sap which leads to general weakening of the plant. Indirect damage is due to the proliferation of sooty mold or fumagina (Capnodium elaeophilum) on the honeydew due to

284

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops feeding, which stains and spoils the fruit as well as complicating normal plant development. Both types of damage become serious when population levels are high Another serious problem is the transmission of the virus by adult insects

VIRUS

INITIALS

VECTOR

Tomato chlorosis virus

ToCV

Bt & Tv

Tomato infectious chlorosis virus

TiCV

Tomato yellow leaf curl virus

TYLCV

Tomato torrado virus

ToTV

Bt & Tv

Table 1: main viruses transmitted by white fly

Preventive Control and Cultural Techniques       

Installation of mesh on greenhouse side walls Clearance of weeds and greenhouse vegetable waste Non-association of crops in the same greenhouse Non-abandonment of shoots at the end of the growing cycle: Young shoots attract adult white fly Placement of yellow sticky traps Use of resistant varieties Release of beneficial insects in the nursery (Nesidiocoris tenuis)

Biological Control Bemisia tabaci: Eretmocerus mundus, Macrolophus pygmaeus, Nesidiocoris tenuis. Trialeurodes vaporariorum: Encarsia Formosa, Eretmocerus eremicus, Macrolophus pygmaeus, Nesidiocoris tenuis. Entomopathogens may also be considered biological treatment. They are organisms which cause diseases in insects and come from very diverse sources: virus, bacteria, fungi, protozoa and nematodes. The problem with entomopathogens is that they do not go actively looking for their hosts, as predators and parasitoids do. Their use is therefore linked to mass production and use as biopesticides. Amongst the entomopathogens with a proven significant effect on white fly are the fungi Aschersonia aleyrodis (Webber), Beauveria bassiana (Balsamo) and Verticillium lecanii (Zimm.). Entomopathogenic nematodes Sterinema feltiae (Filipjev) are also being evaluated.

285

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Chemical Control Paraffin oil, azadirachtin, Beauveria bassiana, oxamyl, Pymetrozine, pyrethrins, pyridaben, pyriproxyfen, spiromesifen, teflubenzuron, thiamethoxam and verticillium lecanii.

2.4 Thrips (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) Adults colonise crops by laying their eggs inside vegetable tissue, in leaves, fruits and, preferably, flowers where the highest levels of adult and larval populations are to be found. Direct damage due to larval and adult feeding is above all on the undersides of the leaves. The affected organs turn a silver colour and then necrotize. These symptoms can be detected when the fruits are affected (above all on peppers) and when the leaves are seriously affected. The eggs can be observed when they appear on fruits (aubergines, green beans and tomatoes). However, the most serious damage is the indirect transmission of the TSWV virus, which also affects peppers, aubergines and green beans. Preventive Control and Cultural Techniques      

   

Use of pest-free vegetable matter Installation of anti-insect mesh on the side walls of the greenhouse and double gates which act as a sluice gate Clearance of weeds and crop waste Handling of spontaneous plants, encouraging conservation and beneficial insects strategies Removal of plants affected by TSWV thus considerably reducing the incidence of viral infection due to a decline in the population of thrips Placement of blue chromatic sticky traps. At least 50 blue and 50 yellow sticky traps should be placed per hectare with special attention being paid to areas prone to pest entrance such as sidewalls and roof vents. When a crop change takes place very quickly, these traps are very effective due to the fact that part of the thrips cycle is carried out on the ground and said traps are very attractive for them in the absence of a crop or when the plants are still very small Use of chromotropic traps with an aggregate pheromone emitter Leave at least two weeks between the removal of the old crop and the transplanting of the new one Use of tolerant varieties Release of beneficial insects in the nursery (Nesidiocoris tenuis)

Biological Control Nesidiocoris tenuis, Macrolophus caliginosus. Hypoaspis miles has been experimented with in cooler seasons on crops in soil.

286

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Chemical Control Paraffin oil, azadirachtin, lufenuron, oxamyl, pyrethrins and spinosad.

2.5 Root-knot nematodes (Meloidogyne spp.) The species of the Meloidogyne genus are polyphagous sedentary endoparasites and are the main nematological problem for horticultural crops in Spain. The intensification of agriculture, greenhouse production and mono-crops, or specialization in a low number of crops, has led to a greater presence of these nematodes. These factors favour the development of the disease due to the virtually year round presence of host plants, the increase of temperatures under covers and short fallow periods which reduce nematode natural death rate. The damage caused by nematodes can reach levels of up to 60 % in production losses. The species M. javanica, M. arenaria y M. incógnita have been identified in the horticultural crops in Almeria. They affect practically all horticultural crops causing the typical root knots. They penetrate the roots from the soil. As the fecundated females’ eggs swell the roots take on a “bubbly” appearance. This, together with the hipertrófia they cause in the root tissues gives rise to the typical “rosary” bracelet. These lesions cause vessel obstruction and prevent absorption by the roots, resulting in lower plant development and the appearance of green wilt symptoms in the hottest part of the day, rising chlorosis and dwarfing, they respond poorly to fertilisation and age prematurely. The symptoms worsen during fruiting since the damaged root system cannot provide the water and nutrients necessary for the fruits. They distribute themselves along lines and are easily transmitted by irrigation water, to footwear, tools and with any means of soil transportation. Furthermore, nematodes interact with other pathogens, either actively (as virus vectors) or passively facilitating the entry of bacteria and fungi through the lesions they have caused. The aim behind the control of the phytoparasitic nematodes is to avoid significant production losses. There are different methods for reducing population levels below the economic damage threshold and/or reducing the reproduction rate (genetic, agronomic, physical, biological and chemical methods). Chemical control using soil fumigants and nematicides has been most commonly used for its rapid action and high efficacy. However, the legislative restrictions on the use of agrochemicals and environmental concerns have led to the prioritization of other methods. However, there is no control method to reduce population densities of nematodes around 90 % consistently and permanent in time. Hence the control must be performed by implementing management strategies which combine several methods for minimizing infestations, seed dispersal and the consequent damage to the crop. The effectiveness of different methods that comprise this strategy should be synergistic and/or complementary and long-lasting, with a low environmental impact, minimal toxicological risk and economically viable.

287

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Measures for reducing population levels prior to planting:    



  

Soil preparation. Keep the ground free of organic matter and weeds Leave the land fallow for a time. The longer the land can rest the more nematodes will die due to lack of food Destruction of previous crops’ roots. Removal of food source for nematodes present in the soil Solarization or biofumigation. It is carried out in areas with hot summers for a period of between 6 and 8 weeks. Biofumigation releases toxic substances and increases the percentage of organic matter Use of nematicides. Those on the market have many days lee time and are recommended for use during transplanting. New, less contaminating active ingredients are required. Use of genetically resistant plants. At soil temperatures of below 27 ⁰C they behave as if they were resistant Adequate transplanting date. Avoid the summer because nematode multiplication accelerates them Crop rotation. Green fertilisers. Crops with nematicidal effects for example sorghum, the roots of which contain dhurrin and which release hydrogen cyanide upon death. Brassicas also produce a substance upon decomposition, called isothiocyanate, which has an effect on nematodes

Measures for reducing population levels after planting: These measures are palliative. They are useful for reducing the multiplication rates of nematodes in crops. 

 



Use of Nematicides. Chemical control is still the most widely used because it is easy to apply. Not all stages of the nematodes are susceptible to these products, only the mobile of vermiform stages die. The eggs are protected by a gelatinous mass and the adults are inside the roots which make them very hard to control with chemical products If the plant is infected the best measure is to end the crop as quickly as possible (short cycle) Use of biological control agents. Population regulation by means of direct action by antagonistc organisms, or their metabolytes, and the induction of plant resistance mechanisms. These organisms include: fungi, bacteria, protozoas, insects and mites Application of organic ammendments. Organic enrichment of the soil, as well as nutrient addition, favours the presence of fungi and bacteria which serve as food for fungivorous nematodes and bacteriphages which are important for soil health

Chemical Control Currently authorised materials: ethoprophos, fenamiphos, fosthiazate and oxamyl.

288

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops

2.6 Leaf miners Leaf miners or submarines currently present in greenhouse horticultural crops are Liriomyza bryonae (in all crops) and Liriomyza trifolii (tomatoes and green beans). Damage caused can be divided into two types: Adult females feed off, and lay their eggs in, the young leaf tissue. This is where the larva begins to develop and feeds off the parenchyma causing the typical galleries. The shape of the galleries is different between species, host plant and number of larvae per leaf although it is not always distinguishable. Once larval development is complete the larvae leave the leaves to pupate, either on the ground or on the leaves, after which they enter the adult phase. The importance of the damage depends on the size of the population, the species itself, the stage of development of the plant and the part under attack (small or large plant). In general, damage causes a reduction in the photosynthetic capacity of the plant, desiccation, necrosis and even premature leaf fall. It can also cause secondary damage via fungal infections and even be a virus vector. Preventive Control and Cultural Techniques       

Installation of mesh on greenhouse side walls, roof vents and gates Installation of double doors Use of healthy vegetable material from authorized nurseries Removal of weeds and crop waste, which could act as reservoirs, from the greenhouse and surrounding areas It would also be advisable to carry out sweeps between crops to remove pupae When attacks are serious, remove and destroy plants’ basal leaves Installation of yellow chromatrophic traps from the beginning of the crop for the early detection of the first attacks

Biological control with natural enemies Native parasitoid species: Diglyphus isaea (Walker) the most commonly released, Diglyphus minoeus, (Walker), Diglyphus crassinervis Erdös, Chrysonotomyia formosa (Westwood), Hemiptarsenus zihalisebessi (Erdös), Cirrospilus vittatus (Walker), Dacnusa sibirica (Haliday). The experimental use of the entomopathogens; (nematodes Heterorhabditis bacteriophora or fungi) is looking hopeful. Chemical Control Abamectin, paraffin oil, azadirachtin, cyromazine, oxamyl and pyrethrins (pyrethrum extract).

2.7 Aphids Several species of polyphagous aphids have been identified in greenhouse tomato crops. he most abundant of which are Myzus persicae (Sulzer) and Aphis gossypii (Glover). They are polymorphous with winged and wingless viviparous females. The wingless females have a

289

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops black siphon and a green or yellowish body while Myzus females are completely green (occasionally brown or pink). They establish colonies and separate into foci which then disperse, mainly in spring and autumn, by means of the winged females. The direct damage is caused by the insects when digging their stiletto mouthparts into the plant tissue until they reach the sap vessels. This leads to a general weakening of the plant when the colonies are very numerous. Damage to plantlets and young plants is especially serious. Indirect damage caused by the secretion of honeydew upon which fungi thrive (sooty mold) and by the transmission of viruses PVY (potato virus Y) and CMV (cucumber mosaic virus). Preventive control and cultural techniques   

Installation of mesh on the side walls of the greenhouse to impede or complicate the entrance of winged females Removal of weeds from the plot and surrounding area (adventitious plants from the borders of the plot) as well as remains of the previous crop Placement of yellow chromatic traps

Biological control with natural enemies 

 

Native predatory species: Aphidoletes aphidimyza, Coccinella septempunctata (Linneo), Adalia bipunctata (Linneo), Chrysopa Formosa (Brauer) y Chrysoperla carnea (Stephens), Syrphidae spp. Native parasitoid species: Aphidius matricariae, Aphidius colemani, Lysiphlebus testaicepes, Aphidius ervi. Purpose-bred parasitoid species released: Aphidius colemani.

Chemical control Paraffin oil, azadirachtin, ethofenprox, flonicamid, oxamyl, Pymetrozine, pyrethrins (pyrethrum extract), pirimicarb, thiacloprid and thiamethoxam.

2.8 Lepidoptera (Caterpillars) Most of the lepidoptera, considered to be horticultural crop pests, belong to the Noctuidae family. Considering the feeding behaviour of these lepidopteran caterpillars they can be classified as defoliating caterpillars (can attack fruit occasionally but usually not staying in them), very voracious consuming large amounts of foliage: Spodoptera exigua, S. littoralis, Autographa gamma, Chrysodeixis chalcites, fruit caterpillars, staying inside and also feeding off stems and leaves: Heliothis armígera (Hübner), Heliothis peltigera (Dennis & Schiff.). The main damage caused by this pest is defoliation which can occur especially in young plantations (defoliating caterpillars) and weakening of the plant due to attacks on shoots and leaves and due to direct economic impact for loss of fruit (fruit caterpillars).

290

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Preventive control and cultural techniques     

Placement of mesh on the side walls of the greenhouse Removal of weeds and crop waste When attacks are serious remove and destroy basal leaves of the plant Placement of pheromone and light traps Keep the first stages of plant development, in which irreversible damage can be caused, well under control

Biological control with natural enemies   

Parasitoids: Trichogramma achaeae (Nagaraja &Nagartakki), Cotesia marginiventris (Cresson) Autochtonous pathogens: nuclear polyhedrosis virus NPV Biological products: Bacillus thuringiensis var. kurstaki and aizawai, Beauveria bassiana.

Chemical control Abamectin, azadirachtin, chlorantraniliprole, emamectin, etrofenprox, flubendiamide, indoxacarb, lufenuron, metaflumizone, methoxyfenozide, pyrethrins (pyrethrum extract), spinosad, tebufenozide and teflubenzuron. Tuta absoluta (Tomato leaf miner) Tuta absoluta (Meyrick) deserves a special mention. The tomato leaf miner (Tuta absoluta Meyrick) is a relatively newly arrived pest which affects mainly tomato crops as well as aubergines and potatoes. When pest pressure is high losses my reach 100 % of the crop and its mere presence may limit exportation possibilities. This pest is originally from South America, it is endemic to most tomato producing regions, where it is one of the most serious problems facing the crop (EPPO, 2005). The first Tuta absoluta were discovered in Spain in 2006 and in 2007 it was identified in other European countries (France and Italy) and Mediterranean (Morocco, Algeria, Tunisia). Tuta absoluta is a small moth, the adults are just less than 7 mm long by 1 mm wide at rest. There is a certain difference in size between individuals. Once the females have mated they lay their eggs from which the larvae hatch. After going through 4 larval stages, at times 5, they become chrysalides from which the moths emerge. In optimum conditions an egg can reach adulthood and lay new eggs in a little more than 20 days. The damage is caused by larvae that penetrate tomato fruits, leaves or stems, which they feed off, at birth, perforating and tunelling. The fruit can be attacked from their formation and may lead them to rot due to the action of secondary pathogens, which enable symptoms to be rapidly seen. However laying normally takes place on the calyx of these fruits when they are green the larvae, which hide just underneath the calyx, are initially difficult to spot.

291

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops On the leaves, the larvae feed on the mesophyll tissue only, leaving the epidermis intact. The mines are irregular and then necrotise. The galleries on the stem affect the development of plants attacked. Once the larval stages have been completed most of the caterpillars drop to the ground to pupate, while some do so directly on the different parts of the plant by the calyx of the fruit, protecting themselves with a small cocoon. Over time the adults are emerge to mate and continue to lay eggs, and can survive well in either crop waste or on the plot in the absence of plants. Due to these survival characteristics greenhouse, and surroundings, vegetable waste control measures are of vital importance to avoid early infections of subsequent crops. It is essential to use all available methods for the control of Tuta absoluta to be effective, since no control method alone is sufficient. It is necessary to combine cultural practices with chemical and biological pest control. In short, the application of an integrated control strategy which decides on the most appropriate course of action at all times.

Preventive control and cultural techniques

   

  

Use pest-free planting material In the case of greenhouses, solarisation of the plot once the tomato crop has finished, to guarantee the elimination of any chrysalids remaining in the soil Selective removal of the organs damaged by Tuta, especially at the beginning of the crop Correct handling of the crop waste and susceptible weeds, not disposing of them either in the greenhouse or on the plot. In the case of protected crops the waste should be kept in closed containers until it is sent to a waste management plant. In open field crops the waste must not be left on the plot Observance of the minimum six week period between each crop cycle for susceptible varieties Do not interrupt crop phytosanitary control until the end of the crop cycle Use mass trapping at the beginning of the crop with low population levels. The use of traps with oil is recommended; between 20 and 40 traps per hectare

Biological control Predators: Nesidiocoris tenuis Reuter. Parasitoids: Trichogramma achaeae (Nagaraja&Nagarkatti), Necremnus artynes Walker

292

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops

Tomato crop diseases

3.1 Fungi 3.1.1 Fusarium wilts (Fusarium oxysporum f. sp lycopersici). Preventive control and cultural techniques       

Crop rotation gradually reduces the pathogen in infected soil Removal of diseased plants and crop residues Use of certified seed and healthy seedlings Use of the nitrogen in nitrate form (it seems to inhibit the growth of fungi) Use of resistant varieties Disinfection of the structures and utensils Solarization

3.1.2 Grey mold (Botrytis cinerea Pers.) Preventive control and cultural techniques  

   

Removal of weeds, crop waste and infected plants Special care should be taken when pruning, making clean cuts always flush with the stem with a knife and avoiding large wounds. If possible, when relative humidity is not very high in the morning when the plants have all day to dry and then to apply a fungicide paste Control of nitrogen and calcium levels, avoiding very vigorous planting Use of plastic greenhouse covers which filter ultraviolet light Use of appropriate plant density to allow aeration Appropriate ventilation management in side walls and especially roof vents and irrigation

Biological control Bacillus subtilis. Chemical control Captan, cipronidil + fludioxonil, chlorothalonil, diethofencarb, fenhexamid, iprodione, mepanipyrim, metiol thiophanate, pyrimethanil and tebuconazole. 3.1.3 Blight (Phytophtora infestans) Also known as cangrene. Preventive Control and Cultural Techniques 

Removal of diseased plants and fruits

293

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops  

Adequate ventilation and irrigation control. Avoid moisture and the presence of water on plant surfaces Use of healthy plantlets

Chemical control Azoxystrobin, Cymoxanil benalaxyl + mancozeb, benalaxyl + mancozeb + copper oxychloride benalaxyl, benthiavalicarb-isopropyl + mancozeb, captan, cyazofamid, cymoxanil, cymoxanil + mancozeb, cymoxanil + mancozeb + copper oxychloride, cymoxanil + tribasic copper sulphate, copper oxychloride cymoxanil + copper calcium sulphate, cymoxanil + chlorothalonil, mancozeb chlorothalonil cymoxanil +, fosetyl cymoxanil + to + mancozeb (cymoxanil + fosetyl to + mancozeb), cymoxanil + metiram, cymoxanil calcium sulphate + copper, chlorothalonil, chlorothalonil + copper oxychloride, mancozeb dimetomorf, folpet + copper + copper oxychloride calcium sulphate, cupric hydroxide, cupric hydroxide + mancozeb, cupric hydroxide + copper oxychloride, mancozeb, mancozeb + metalaxyl, mancozeb + copper oxychloride, mancozeb + copper + copper oxychloride calcium sulphate, calcium sulphate mancozeb + copper, mandipropamid, maneb, maneb + copper oxychloride, copper sulphate + calcium maneb, metalaxyl m + copper oxychloride, metiram, copper oxychloride, copper oxychloride + propineb, calcium copper oxychloride + copper sulphate, cuprous oxide, copper calcium and tribasic copper sulphate propineb sulphate. 3.1.4 Powdery mildew (Leveillula taurica (Lev.), Oidium neolycopersici) Cultural techniques   

Removal of damaged basal leaves Adequate ventilation management. Use of sulphur sublimators

Biological control Ampelomyces quisqualis. Chemical control Azoxystrobin, sulphur, sulphur + cyproconazole, sulphur + myclobutanil, bupimirato, cyproconazole, flutriafol, kresoxim methyl, thiophanate-methyl, myclobutanil, penconazol, tebuconazole, tetraconazole, triadimenol, trifloxystrobin. 3.1.5 Cladosporiosis (Fulvia fulva (Cke.)) It causes light green to pale yellow patches on the lower leaflets of the plant as well as a whitish, later turning to brown, down on the undersides. The patches finally necrotize and the leaves curl up.

294

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Preventive control and cultural techniques  

Maximum airing of covers to reduce ambient air humidity to below 85 % Pruning of basal leaves helps eliminate the first infected leaves and encourages air circulation

Chemical control Azoxistrobin, tebuconazol. 3.1.6 Early blight (Alternari dauci f.sp. solani (Sokaner)) Preventive control   

Use of healthy plantlets Removal from the plot of fruits and vegetable waste showing symptoms of disease Adequate ventilation and irrigation management.

Chemical control Azoxystrobin, benalaxyl + cymoxanil + mancozeb, benalaxyl + mancozeb, benalaxyl + copper oxychloride, captan, cymoxanil + mancozeb, cymoxanil + mancozeb + copper oxychloride, cymoxanil + tribasic copper sulphate, cymoxanil + copper oxychloride + sulphate, copper calcium, cymoxanil + chlorothalonil + mancozeb, cymoxanil + metiram, cymoxanil + copper calcium sulphate, chlorothalonil, chlorothalonil + copper oxychloride, difenoconazole, folpet + copper oxychloride + copper calcium sulphate, cupric hydroxide, cupric hydroxide + mancozeb, cupric hydroxide + copper oxychloride, mancozeb, mancozeb + metalaxyl, mancozeb + copper oxychloride, copper oxychloride + mancozeb + copper calcium sulphate, copper calcium sulphate + mancozeb, mandipropamid, maneb, maneb + copper oxychloride, copper calcium sulphate + maneb, metalaxyl m + copper oxychloride, metiram, copper oxychloride, + propineb copper oxychloride, copper oxychloride + copper calcium sulphate, cuprous oxide, and propineb. 3.1.7 Stem and root rot (Phytium spp y Phytophthora spp.) Preventive control and cultural techniques    

Localised application of fungiceides and limitation of irrigation at times favourable for the development of rot Airing of the greenhouse and climate control of same Removal of diseased plants Balanced plant fertility to be maintained

Biological control Trichoderma harzianum, T. asperellum.

295

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Chemical control Dithianon, diodina, etridiazole, fosetyl aluminium + propamocarb, thiophanate methyl, pencycuron, prochloraz.

3.2 Bacteriosis Bacterial speck (Pseudomonas syringae pv. tomato (Okabe)), Tomato pith necrosis (Pseudomonas corrugata (Roberts&Scarlett)), Bacterial canker (Clavibacter michiganensis (Smith)) and soft rot (Erwinia carotovora subsp. carotovora (Jones). Control measures       

Removal of weeds and diseased plants and fruits Adequate ventilation and irrigation management, maximum reduction of atmospheric humidity and absence of water on plant surfaces Use of healthy or disinfected seeds and healthy plantlets Balanced fertilisation Use of copper-based pastes on crop lesions and damage Disinfection of tools No pruning or cutting in high relative humidity. Cuts must be as close as possible to stem

Chemical control Azibenzolar-S-methyl, cupric hydroxide, cupric hydroxide + copper oxychloride, copper oxychloride, cuprous oxide, copper calcium sulphate and tribasic copper sulphate.

3.3 Virus 3.3.1 Tomato yellow leaf curl disease (TYLCD) Control measures    

  

Virus transmission vector control Use of chromotropic traps (yellow sticky tapes) to register the presence of white fly Use of resistant and/or tolerant varieties In the case of greenhouse crops, avoid planting where there have previously been ornamental plants such as poinsettia (Euphorbia pulcherrima) and gerbera because TYLCD has been detected in both species Clearance of previous crops Removal of weeds which could harbour the disease Use of anti-mosquito mesh and thermal blankets

296

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops 3.3.2 Pepino mosaic virus (PepMV) Control measures Establishment of health and control measures in nurseries.        

 

Application of disinfectants (Trisodium phosphate 10 % and bleach solution) on greenhouse structure that has come into contact with infected plants Disinfection of pipes with hot water Hygiene of facilities and utensils Removal of vegetable waste, including roots, of previous crops prior to the planting of new crops Destruction of substrates from areas where virus was detected in the previous crop Carry out tasks following the same route through greenhouse aisles and rows, disinfecting gloves and hands after each row It is recommended that the greenhouse be divided in sectors, each with its own, exclusive, set of tools and clothes Once an infected plant has been located it must be grubbed up, using disposable gloves, with as much of the root system as possible and placed in a plastic bag which must be immediately sealed and destroyed together with the gloves. The clothes must then be disinfected. It is also advisable to grub up neighbouring plants Placement of footwear disinfection mats at greenhouse entrances Removal of all prunings and stripped leaves

3.3.3 Tomato chlorosis virus (ToCV) Control measures   

It is impossibel to erradicte from the crop once established White fly level control Due to the lack of specific symptoms, early laboratory detection is essential to be able to identify, and then remove, the first infected plants

References Andrés, M. F. y Verdejo, S. 2011. Enfermedades causadas por nematodos fitoparásitos en España. Edita: Phytoma. 253 p. Blancard, D. Enfermedades del tomate. 2011. Edita: Mundi prensa. 680 p. Infoagro. El cultivo del tomate. www.infoagro.com Planas de Martí, S. Aplicación sostenible de productos fitosanitarios. 2013. Edita Eumedia. 317 p. Magrama. 1991. Las plagas del tomate: Bases para el control integrado. Edita: Ministerio de Agricultura, Pesca y Alimentación. 194 p.

297

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

The integrated pest and disease management of tomato crops Magrama. 1993. Las enfermedades del tomate: Bases para el control integrado. Edita: Ministerio de Agricultura, Pesca y Alimentación. 214 p. Navarro, V.; Lara, L., y Fernández, M. M. 2011. Colección de fichas de organismos de control biológico en cultivos hortícolas protegidos. Consejería de Agricultura y Pesca de la Junta de Andalucía, Instituto de Investigación y Formación Agraria y Pesquera. (Formato digital). 48 p. Navarro, V.; Lara, L., y Fernández, M. M. 2011. Colección de fichas de plagas en cultivos hortícolas protegidos. Consejería de Agricultura y Pesca de la Junta de Andalucía, Instituto de Investigación y Formación Agraria y Pesquera. (Formato digital). 36 p. Robledo, A.; Van der Blom, J.; Sánchez, J. A. y Torres, S. 2009. Control biológico en invernaderos hortícolas. Edita: Coexphal. 176 p. Tello, J. C. y Camacho, F. 2010. Organismos para el control de patógenos en los cultivos protegidos. Edita: Fundación Cajamar. 528 p. Verdejo, S. 2009. Manejo integrado de nematodos. Revista Horticultura 213. 10-12.

298

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Agrochemical container management

Agrochemical container management Victorino Martínez Puras SIGFITO Sustainable agriculture aims to produce safe foods, to guarantee economic viability so that the farms may be self-sufficient, whilst creating employment and, above all, contributing to the conservation of natural resources. To achieve these goals, the use of the inputs must be exercised with both caution and rigour. The use of phytosanitary products has been established in modern agriculture as a fundamental practice to improve plant health and to ensure the quality of agricultural produce. The incipient use of phytosanitary products raises the issue of what to do with the empty industrial containers. Traditionally, “the correct way” to dispose of these phytosanitary containers was to abandon them near to rivers or even to incinerate them. It was not until the advent of Law 11/1997 when the Government began to give legal coverage to the management of packaging in Spain. However, the measures adopted in the text did not require the makers of the phytosanitary products to adhere to it and include their containers. Three years later Law 14/2000 was passed allowing the exception to be added to the first additional provision in Law 11/1997, that packaged phytosanitary products should be marketed through a “Deposit-Refund” or an “Integrated Management System” (IMS or in Spanish SIG). This exception was made official through the Royal Decree R.D. 1416/2001, concerning phytosanitary product containers, leading to the creation of SIGFITO, the system of packaging collection in which the product consumers must deposit the empty containers at designated collection points, generally located in co-operatives or phytosanitary product commercialization and distribution companies.

299

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Agrochemical container management

The text specifically helps to strengthen the raising of awareness of the SIGFITO collection system. What were previously recommendations for good practices for growers have now become an obligation.

“A waste-free countryside is more productive”. This phrase sums up the essence of the work carried out by SIGFITO Agroenvases, a not-for-profit entity that is working to make the task of recycling agricultural packaging in rural areas easier, ensuring its sustainability. SIGFITO is an agricultural container collection system which contributes to more competitive and more environment friendly agriculture. It is also the first integrated system for the management of agricultural containers to be created in Spain. It prevents the pollutant elements of this type of product from harming rural areas, the environment and the living beings that inhabit it. After using the product, professional growers should be very meticulous and rinse out the liquid containers three times, pouring the water into the sprayer tank. This practice ensures that the container is completely clean when it arrives at the recycling plant.

Omitting this process, through neglect or reluctance to comply, may mean that the product comes into contact with other elements that can contaminate the rural environment. SIGFITO has a network of more than 3.000 collection points. These points are mainly phytosanitary products shops or distributors, agricultural cooperatives and major producers amongst others. Logic has it that growers drop off their used containers, mainly, where they acquires the new product. The participation of these entities in SIGFITO is voluntary and is regulated through a collaboration agreement.

300

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Agrochemical container management

The collection point agrees to comply with a series of requirements to collect and store the containers safe and securely. These entities offer a service of great added-value to their clients or members, acquiring a competitive advantage since the growers are required to return the containers and there is a growing demand for this service. Also, at these collection points, the growers must obtain a delivery receipt as legitimate proof of compliance. It is very important that the farmers take the containers bearing the SIGFITO logo as they are the only ones accepted at the collection point. The user must scrupulously separate any damaged and empty containers putting them into plastic bags, separate the product residues and those of any accidental spills that may occur, until they are delivered to the corresponding waste management point. Phytosanitary products must be kept sealed in an upright position, with the opening facing upwards and the original label must be complete and legible. Once the container has been opened, if the contents are not completely used up they should be kept in the same container, with the top sealed and the original label complete and legible. Once the used containers are empty, the farmer should store them in a bag for later transportation to the SIGFITO collection point. The work of these drop-zones is fundamental for this collection system to function properly. There, an agricultural technician will ascertain that the containers do not contain any type of residue. The same person will be responsible for providing the grower with a delivery receipt, either on paper or electronically, which proves that the grower has handed over the containers according to regulations. This digital certificate bears the SIGFITO logotype and is legal proof that the phytosanitary containers have been correctly managed by the grower. It is very important to know that this document must be kept for a period of three years. Also, with the new legislation, phytosanitary product points of sale also become information points to provide advice to the growers on the use of the products and about the nearest SIGFITO collection points. Therefore, growers should have sufficient information to know what to do in order to recycle the SIGFITO containers.

301

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Agrochemical container management

Once the containers are collected, they are taken to the treatment plants where they begin the recycling process to become plastic pipes, plant pots and new containers. Another destination for these containers is to obtain energy from this waste. This process is known as energy recovery. SIGFITO also plays a fundamental role in the transfer of material. It ensures that the transfer of collected containers is carried out correctly so as to avoid any damage to them in transit. SIGFITO is financed by the producers and packagers of phytosanitary products, in compliance with their legal obligation to manage their containers through a collective system such as SIGFITO. The companies that do not market phytosanitary products can participate in a voluntary way by including their own containers of fertilisers, seeds, plant, food, etc. in the system. These participating companies make a proportional contribution to the weight of the containers that they market; there are currently more than 100 companies participating in the System. All contributions received go towards paying for the cost of the collections, the transport and enhancing container value. The entire domestic market for these products adheres to SIGFITO. In turn, these companies include the SIGFITO logo on their product labels, which identifies their containers as recyclable through the system’s collection points.

302

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability

Certification & traceability Francisco Guillén Salmerón Proyecta Ingenio S.L.

The concept of quality is very dynamic and constantly growing more complex. Whereas no more than 20 years ago the quality parameters were related to the characteristics of the product, such as size, colour, appearance and flavour, today the concept is much wider and embraces other aspects, including links in the supply chain, environmental criteria, social considerations, health and safety at work, food safety, healthiness, etc. This dynamism in the concept of quality demands that the various stakeholders in the supply chain be capable of reacting rapidly, even proactively and agile in the adoption of measures to comply with the quality criteria. A production area which cannot assimilate the development of the concept of quality will lose market share to the point of vanishing, and this is true especially in a market as globalized as the modern one and one in which climatic conditions, though they remain a limiting factor, are no longer an insurmountable barrier. Furthermore, this quality must be reliably supported by a certification system undertaken by an independent entity. The first-party certification (that which is undertaken by the enterprise itself), just like the third-party certification (that offered by the customer), cannot be considered reliable for various reasons:  

First-party certification, because it is undertaken by the producer, lacks all credibility Second-party certification may have a preconceived outcome. The results of this assessment is the acceptance (or otherwise) of a producer as a supplier. If the customer who makes the assessment for us has already had his supply needs met, the outcome of the assessment will be very different than if this same customer urgently needs to expand the number of suppliers to cover requirements

Third-party certification, that which is carried out by an independent entity rather than by producer or customer, is the one which guarantees that entities receiving it meet the minimum standards required by the regulations or the accepted standards. Almeria is a good example of adaptation. In many cases, this has come about as a reaction to problems, and in many others as a result of the industry’s proactive outlook. As an example of reaction, it is appropriate to mention here a health alert which started in early 2007, and concerned a phytosanitary product used in the growing of peppers, and which led to one of the worst crises the industry has experienced. The sector responded rapidly and by September, the province of Almeria was managing some 50 % of its pepper production using integrated control techniques, which spectacularly reduced the incidence, not only of this active ingredient as a question of fact, but also of other substances, even though they were not tightly regulated (it was decided to abandon the use of these because they were not compatible with natural predators). This fact in its turn 303

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability led to a revolution in the fields of Almeria, so much so that one can now say that 80 % of peppers produced here are grown under integrated control techniques. However, far from this being a development which has inconvenienced the industry, it has brought about a radical shift in perception on the part of producers. Through integrated control, they have learned to work with pests and their natural enemies, managing them in a way that is in harmony with production. The fact that integrated control has worked well in pepper production has inspired producers to apply these techniques to other important local crops such as tomatoes (it is now estimated that more than 50 % of the land producing tomatoes is managed using integrated control). Integrated control has established itself as the method which the producers all want, and in terms of both land area and range of products, the proportion of the industry which is using these techniques is growing constantly. The implementation of integrated pest control techniques has resulted in a substantial improvement in the way society in general perceives agricultural production in the province, as with the reduction in the number of samples showing excess MRLs.

Figure 1: Percentage samples exceeding the UE MRLs in the EU- programme by origin country (only EEA countries) Source: EFSA report 2013

But not all the changes have arisen from crisis situations. The industry knows how to anticipate market changes and has adopted measures which, even if they have not always been popular, have without doubt helped to keep our agriculture in the vanguard both in terms of technology and quality. As an example of this, we can mention all the traceability requirements demanded by Regulation 178/2002, which had already been met by more than 90 % of the exporting businesses of our province, even before they come into force. It should also be added that Spanish laws on traceability, hygiene and food safety are among the strictest to be found anywhere. The so-called “hygiene package”, and specifically the publication of Regulation 852/2004 (food product hygiene), has had practically no effect on foodproducing companies, because Spanish legislation had already anticipated these requirements and, in many cases, had imposed even stiffer standards than those set out in the Regulation. 304

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability Every Spanish company intending to produce foodstuffs must put in place: 



A “Self-monitoring system” which meets a number of requirements set out in so-called “General Hygiene Plans”. Further, this self-monitoring system must be rounded off with a “Hazards and Critical Points of Control System of Analysis”, which identifies every hazard (physical, chemical and microbiological) which could possibly affect the product, and establishes preventative measures to reduce or eliminate the identified hazards A traceability system which will be capable of identifying both the supplier of raw materials and the recipients of the final product, as well as every phase through which the product has passed, along with its bottling or packaging materials and additives An Employee-Hazard Prevention Plan

In some cases these legal requirements are not adequate for certain markets, which require businesses who intend to export their products to meet with additional stipulations. However, it is certainly true that the requirements of Spanish law place Spanish companies in an excellent position to comply with the great majority of customers’ demands. However, it is not enough just to do things well. They must also be shown to be done well. This is where standardization, in addition to certification, comes into play. Standardization is the process of setting standards, but who sets the standards? By 1995, the production sector had already begun to realize that doing things well also required making this fact known and, to this end, COEXPHAL (the largest producers’ association in Almeria) set out to draft a standard which would:   

Improve the production and handling system Make these improvements widely-known Provide an objective communication tool for the certified companies.

All of this was to be achieved with transparency and with the cooperation of all the interested parties. The result of all this work was the creation in 1996 (through AENOR, the Spanish Standards Association) of the CTN155 Committee whose brief was to draw up a Good Agricultural Practices Standard. Using this Standard, the Committee would act as a guide to businesses and producers looking to improve their production practices and, once this objective was achieved, would go on to be an independent certifying body carrying out the work of assessing and certifying the implementation of these good agricultural practices. Thus, Standard UNE 155000 (Fresh fruits and vegetables. Controlled production. General requirements) came into being. Each of the following interested parties is represented on this standardization committee: Producers, retailers (GLOBALG.A.P.), laboratories, phytosanitary businesses and even the state

305

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability

administration, in order that the Standard meets the needs of, and is helpful to, all the interested parties. This Standard is a reference point for the Spanish fruit and vegetable industry and enjoys wide recognition among the main distribution chains. Taking full advantage of the review of UNE 155000 which was due to take place in 2008 in order to maintain harmonization with GLOBALCAP, and in order to respond to the demands of customers and producers alike (with regard to integrated pest control practices), UNE 155000 widened its spectrum of certification options to include voluntary certification of “biological pest control”. Thus, UNE 155000 became the first Standard to approve the control of pests through biological means. At the same time as UNE 155000 was being prepared, a group of retail distribution chains, united under the title, “Euro Retailer Working Group” (EUREP), drafted its own protocol of good agricultural practices, entitled EUREP-G.A.P. (now GLOBALG.A.P.). The following businesses make up this group of retailers:

Figure 1: GLOBALG.A.P. Retailer/Foodservice Members.

All the members of this group of retailers reached agreement that, as of 1 January 2004, every supplier would have to be certificated under one of GLOBALG.A.P.’s certification options. This meant a considerable expansion in the number of businesses, producers and land area subject to GLOBALG.A.P. certification.

306

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability

The UNE 155000 Standard achieved harmonization with the GLOBALG.A.P. protocol in 2001, the year which saw a major expansion of the land area subject to certification - an increase which was due precisely to this recognition of GLOBALG.A.P.’s authority.

2970,0

2011

2010

2575,0

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

2780,0

Lucha Biológica

Superficie máxima (ha)

Total

Chart 1: fruit & vegetable production land surface area controlled by AENOR

Keys = Lucha biológica: biologic control

And that is why today, any fruit and vegetable enterprise whatsoever which would like to sell its goods in Europe has to reckon with, at the very least, being certified by GLOBALG.A.P. In addition to GLOBALG.A.P. certification, the Enterprise will have to comply with other standards and protocols in order to attend to its customers’ needs. In a list which is not exhaustive, here are the most frequently insisted-upon standards, along with the clients who demand them:      

Nurture: Tesco QS: Aldi, Tengelmann & Edeka Leaf: Waitrose BRC: English Distributors IFS: French, German & Italian Distributors Field to Fork: Marks & Spencer

It is very usual for a business to have to comply with various certifications in order to meet the needs of its clients. Thus, for example, a company which markets its goods in the UK will have to obtain GLOBALG.A.P. certification and, if it wants to sell to Waitrose, it will also need to meet the requirements of the LEAF protocol. Although there is a multiplicity of certifications, they all tend to have the same objectives and, allowing for the market they are aimed at, will coincide in most aspects. Generally, certification requirements cover: 

Good agricultural practices

307

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

Certification & traceability     

Environmental protection Employee safety Health & nutrition Social responsibility Product quality

Since these different standards and protocols are so very similar, the certifying bodies have adapted, and hold meetings in which they analyse the various standards, thus achieving a major cost savings for the businesses. The aspects of the standard most likely to apply will depend on the production area and the sensitivity of the target market. On many occasions, this market sensitivity is estimated by means of campaigns of doubtful credibility on the part of interested parties but, independently of this, it is the producers who must supply evidence of having complied with all requirements of the customer, and must show this in a manner which must be verifiable, as certification requires. Certification is a tool which enables businesses to demonstrate to their customers and to society a commitment and a meeting of expectations. This tool should be used by businesses to inspire trust on the part of the customers they currently have, to open new markets, to guarantee the maintenance of quality in its broadest sense and to be in a position to adapt to the changing needs of the marketplace. The development which the fruit and horticultural produce industry in Almeria has undergone would not have been possible without the great efforts of producers to carry out their work in the very best way, always striving to exceed the expectations of their customers. However, these efforts would have been less recognized, had the producers not sought the support and validation of their hard work through independent certifying bodies which guarantee that demands for quality are being met.

308

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

AUTHORS

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

PROJECT RATIONALE

ALMERIA, AN EXAMPLE OF INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

1 2 3 4 5

Introduction 10 Current situation in the Mediterranean arc: Almeria, an example of a hard task done well10 Key factors behind the success of integrated pest management in Almeria 13 Current situation - supermarket demands 14 Challenges and opportunities for drop protection over the next decade 16

GREENHOUSE STRUCTURES

1 Introduction 2 Principal types of greenhouse in the Mediterranean Basin 2.1 Locally made or crafted greenhouses 2.2 Plastic covered industrial greenhouses 2.3 Glass greenhouses 2.4 Conclusions on greenhouse structures

18 18 18 20 20 21

GREENHOUSE COVERING MATERIALS IN THE MEDITERRANEAN

1 Introduction 2 Plastic materials for greenhouse coverings 2.1 Polymers 2.2 Additives 3 Photoselective properties of greenhouse coverings 3.1 Stabilization against ultraviolet light 3.2 Clear and diffuser plastic 3.3 Thermoplastic 3.4 Anti-drip plastic 3.5 Anti-heat plastic 3.6 Anti-pest plastic

23 24 24 24 25 25 25 26 27 27 28

GREENHOUSE VENTILATION AND COOLING

1 Introduction

309

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

2 Natural ventilation 2.1 Wind condition: calm 2.2 Wind effect ventilation 2.2.1 Visualisation experiments

2.3 Cooling by water vapour evaporation

31 31 31 31

GREENHOUSE CLIMATE CONTROL

1 Introduction 2 Energy requirements 3 Heating systems 3.1 Convection heating systems 3.2 Conduction heating systems 3.3 Convection and radiation heating systems 3.4 Metal pipe hot water system

34 35 35 35 37 38 38

GREENHOUSE TECHNOLOGY & INTEGRATED PEST MANAGEMENT

1 2 3 4

Introduction Greenhouse structures & plastic photoselective and anti-pest materials Anti-insect meshes Cooling techniques and pest control

42 43 46 52

SOIL CULTIVATION: CHARACTERISTICS, CORRECTION AND DISINFECTION

1 Soil 1.1 Soil fertility 1.2 Soil sampling 1.3 The optimum soil 1.4 Possible soil problems 1.5 Soil preparation 1.6 “Enarenado” or sanded soil 1.7 The basis of soil sanding 1.8 Carrying out the soil-sanding process 1.9 Chracteristics of sand to be used 1.10 “Enarenado” Soil-sanding operation 2 Soil disinfection 2.1 Sustainable, environmentally friendly systems

63 63 63 64 66 67 68 68 70 75 75 78 81

2.1.1 Steam 2.1.2 Solarisation 2.1.3 Biofumigation or biodisinfection

2.2 Chemical disinfection 2.2.1 Considerations for the carrying out of chemical disinfection

81 82 84

86 86

310

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

2.2.2 Considerations before sowing or transplanting

3 Fumigants available 3.1 Dazomet 3.2 Metam sodium y Metam potassium) 4 Annex. Calculation of the amount of water needed for solarisation.

87 87 88 89

THE IRRIGATION OF GREENHOUSE CROPS

1 2 3 4

92 92 93 93 94 95 95

Introducción Where the water originates Systems of irrigation and water storage Irrigation water supply 4.1 Indicators of irrigation water use 5 Programming in-greenhouse irrigation 5.1 Programming irrigation by means of sensors 5.1.1 Programming Irrigation with soil moisture sensors 5.1.2 Programming irrigation with plant sensors 5.1.3 General considerations: sensors in irrigation management

5.2 Programming irrigation, using climatic data 5.2.1 Models for estimating the crop water requirements

FERTIRRIGATION 1 2 3 4 5 6 7 8

96 99 99

100 100

105

The Concept of fertirrigation 105 Criteria for fertirrigation in soil 106 Criterion of fertilizer application, according to the crop’s theoretical needs 106 Criterion for fertilizer application, based on an ionically balanced physiological solution 108 The problem of nitrates, and its relationship with agricultural activity 113 Legislation governing nitrates in agriculture 113 Agricultural practices which contribute to the leaching of nitrates 114 Agriculture practices for optimal management of nitrogenous fertilizers 114

SOILLESS CROP MANAGEMENT

117

1 2 3 4 5 6

117 119 120 125 126 131

Preparing and commencing cultivation Irrigation management at the beginning of the crop Subsequent irrigation management Automation of irrigation Design of the nutrient solution Crop monitoring

WASTE, OR PRODUCTS WITH OTHER QUALITIES AND DIFFERENT USES?

134

311

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

1 Summary 2 Breakdown of products generated by a greenhouse 3 Re-using byproducts - a theortetical framework 3.1 Plastics 3.1.1 String (raffia) 3.1.2 Plant pots 3.1.3 Covering plastic

134 134 136 136 136 137 137

3.2 Metals 3.3 Incineration 4 The practical example of organic matter: compost production 4.1 Introduction to the process of composting 4.2 Types of crop waste, frequency, quantity, quality and problems 4.3 Composting solutions 4.4 Examples 4.5 Ways of measuring the quality and suitability of the product

138 138 138 138 139 141 143 144

OPTIMISING THE APPLICATION OF PHYTOSANITARY PRODUCTS IN GREENHOUSES

149

1 2 3 4 5

Introduction The influence of application equipment The influence of the nozzle type Influence of the volume of application Acknowledgements

149 150 154 155 156

MANAGING RESISTANCE TO INSECTICIDES

158

1 2 3 4 5 6

158 158 160 162 164 165

Introduction Concept of pest resistance Development of resistant populations Resistance mechanisms A growing problem Resistance management strategies

GREENHOUSE PEST AND DISEASE CONTROL: SUBLIMATORS

168

BIOLOGICAL CONTROL IN GREENHOUSES

179

1 Introduction 179 2 Biological pest control 181 3 Biological control agents 182 4 The main pest infestations found in crops grown under plastic in SE Spain and their natural enemies 183

312

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

5 Biological control management in the greenhouse 6 Development of a strategy for biological control through conservation within the framework of southeastern Spain’s intensive horticulture

189 190

BEST AGRICULTURAL PRACTICES IN THE GREENHOUSE: THE KEY TO SUCCESS IN INTEGRATED PEST CONTROL MANAGEMENT 192 1 2 3 4 5

Introduction Prevention - cultural measures Crop monitoring Good crop and natural enemy management A biological control programme: recommendations 5.1 Prior to planting 5.2 During cultivation 5.3 From planting to the start of the releases 5.4 Rational chemical control 6 Rational chemical control compatible with biological control

192 192 194 198 199 199 200 201 201 202

DISEASES AFFECTING THE MAIN HORTICULTURAL CROPS IN THE GREENHOUSES OF ALMERIA 205 1 Introduction 2 Relevant bacteria in the horticultural crops of Almeria 2.1 Airborne bacteria 2.1.1 Pathogenic plant species belonging to the genus Pseudomonas 2.1.2 Plant species belonging to the genus Xanthomonas

2.2 Pith necrosis bacteria 2.2.1 Pectobacterium carotovorum subsp. carotovorum 2.2.2 Pseudomonas corrugata

2.3 Vascular bacteria 2.3.1 Pathogenic plant species belonging to the genus Clavibacter 2.3.2 Ralstonia solanacearum 2.3.3 Pathogenic plant species belonging to the genus Curtobacterium

3 Important fungi in horticultural nurseries 3.1 Fungi affecting root system and crown 3.1.1 Pathogenic plant species belonging to the genus Pythium 3.1.2 Pathogenic plant species belonging to the genus Phytophthora

3.2 Fungus affecting vascular system 3.2.1 Pathogenic plant species belonging to the genus Fusarium

3.3 Airborne fungi 3.3.1 3.3.2 3.3.3 3.3.4

Didymella bryoniae Botrytis cinerea Diseases caused by oidia Diseases caused by mildew

205 206 206 206 209

211 211 213

213 214 215 216

216 216 216 217

220 220

222 223 223 224 226

313

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

4 Important viruses in horticultural crops in Almeria 4.1 Viruses transmitted by contact

228 228

4.1.1 Tobamovirus 4.1.2 The Pepino Mosaic Virus PepMV

228 230

4.2 Thrips-borne viruses 4.2.1 Tomato spotted wilt virus (TSWV)

4.3 White fly-borne viruses 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5

Tomato yellow leaf curl disorder (TYLCD) Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TiCV) Tomato “torrado” virus (ToTV) Cucurbit yellow stunting disorder virus (CYSDV) Cucumber vein yellowing virus (CVYV)

4.4 Aphid-borne viruses 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5

231 231

232 232 234 235 236 237

238

Cucumber mosaic virus (CMV) Potato virus Y (PVY) Zucchini yellow mosaic virus (ZYMV) Papaya ringspot virus (PRSV) Watermelon mosaic virus-2 (WMV-2)

239 240 241 243 244

4.5 Cucurbit aphid-borne yellowing virus (CABYV) 4.6 Soil vector-borne viruses

245 246

4.6.1 Melon necrotic spot virus (MNSV)

246

5 Disease control 5.1 Pathogen access control 5.2 Curbing the spread of pathogens that have entered the greenhouse: 5.3 Inter-season pathogen control:

247 248 249 250

INTEGRATED PEST AND DISEASE MANAGEMENT IN PEPPER CROPS

254

1 2 3 4 5 6 7 8 9

254 254 255 259 261 263 264 266 268 268 270 270 272 273 274 275

Definition Identification of phytopathological problems in peppers White tobacco fly (Bemisia tabaci) Western flower thrips (Frankliniella occidentalis) The spider mite (Tetranychus spp.) The broad mite (Polyphagotarsonemus latus) Defoliating caterpillars Aphids Secondary pests 9.1 Pseudococcidae (Phenacoccus solani & Phenacoccus madeirensis) 9.2 Ants (Tapinoma nigerrimun) 9.3 Stink bug (Nezara viridula) 9.4 Boll shedder bug (Creontiades pallidus) 9.5 Lesser pepper fruit fly (Atherigona orientalis) 9.6 Green mosquito (Empoasa spp.) 10 Powdery mildew disease (Leveilulla taurica)

314

INTEGRATED PEST MANAGEMENT IN MEDITERRANEAN GREENHOUSES

11 Grey mould (Botrytis cinerea)

278

THE INTEGRATED PEST AND DISEASE MANAGEMENT OF TOMATO CROPS

282

1 Introduction 2 Most common tomato crop diseases 2.1 Mites 2.2 Tomato russet mite: Aculops lycopersici (Massee). 2.3 White fly 2.4 Thrips (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) 2.5 Root-knot nematodes (Meloidogyne spp.) 2.6 Leaf miners 2.7 Aphids 2.8 Lepidoptera (Caterpillars) 3 Tomato crop diseases 3.1 Fungi

282 283 283 284 284 286 287 289 289 290 293 293

3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 3.1.7

Fusarium wilts (Fusarium oxysporum f. sp lycopersici). Grey mold (Botrytis cinerea Pers.) Blight (Phytophtora infestans) Powdery mildew (Leveillula taurica (Lev.), Oidium neolycopersici) Cladosporiosis (Fulvia fulva (Cke.)) Early blight (Alternari dauci f.sp. solani (Sokaner)) Stem and root rot (Phytium spp y Phytophthora spp.)

3.2 Bacteriosis 3.3 Virus 3.3.1 Tomato yellow leaf curl disease (TYLCD) 3.3.2 Pepino mosaic virus (PepMV) 3.3.3 Tomato chlorosis virus (ToCV)

293 293 293 294 294 295 295

296 296 296 297 297

AGROCHEMICAL CONTAINER MANAGEMENT

299

CERTIFICATION & TRACEABILITY

303

315