Vol 15 No 4
R40.00 (RSA) VAT incl.
BI-MONTHLY MAGAZINE FOR GREENHOUSE, TUNNEL, SHADE NET AND Hydroponics FARMERS
• Potato Seed Production in Greenhouses • Precision Agriculture: Drivers of Revolution • Climate Control: Vents or Pad & Fan?
U N D E R C O V E R F A R M I N G
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• The Right Choice of Grow Media for your Hydroponics System
Your guide to intensive farming • u gids tot intensiewe boerdery
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• What Effect does Winter 1 have on Greenhouse Production?
Contents • Inhoud
Please take note of the new contact e-mail addresses for Nufarmer Africa and Undercover Farming magazines. Kindly amend your address list on your e-mail system accordingly. Thank you! suzanne@axxess.co.za for all communications pertaining to Undercover Farming and Nufarmer Africa magazines editors@axxess.co.za for all press releases, editorial content expo@axxess.co.za for all communication pertaining to Undercover Farming Expo & Conference and Special Projects management@axxess.co.za for all communication pertaining to finance and administration magazine@axxess.co.za for all communication pertaining to marketing, sales and subscription to Nufarmer Africa and/or Undercover Farming magazines We apologise for any inconvenience in this instance but ensure you of improved e-mail communication in future. Suzanne Oosthuizen; Director PROPRIETOR / ADVERTISING SUZANNE OOSTHUIZEN 012-543 0880 / 082 832 1604 Email: suzanne@axxess.co.za EDITORIAL CONTENT & COMPILATION Johan Swiegers 082 882 7023 editors@axxess.co.za ADDRESS PO Box 759, Montana Park 0159 E-MAIL magazine@axxess.co.za FAX 086 518 3430 ADDRESS PO Box 759, Montana Park 0159 DESIGN Fréda Prinsloo PRINTING Business Print Centre Undercover Farming accepts no responsibility for claims made in advertisements or for opinions and recommendations expressed by individuals or any other body or organisation in articles published in Undercover Farming. Copyright is reserved and the content may only be reproduced with the consent of the Editor.
GREENHOUSE CHAT...
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he political journalism around land issues unfortunately makes headlines and in some cases might influence the less strong willed person negatively, but there are so many positive issues at hand that if we focus on these and our greenhouse production, we are bound to survive the issues as people have to eat. The minority of people who are led by the nose and are willing to commit them to anti-social and criminal activities will always be there in the days we live in; globally. To be a producer of foodstuffs to many is an honourable and profitable career. It is therefore imperative to focus on what you are doing and the way in which you are doing it. Yes, we have to deal with issues on water, electricity, changing climate conditions, but that is what makes agriculture in its various forms such an exciting industry. I used to have an MD that referred to managers making things happen in the company as ‘the distinction between men and boys’. Sadly the South Eastern Cape still experience serious drought problems but there are farmers that survive! Why? They learnt to cooperate. In the previous Undercover Farming we had a story of a farmer on the West Coast that has no water at all on his farm for his greenhouses – he is a major cucumber producer. But four farms away is a farm with a strong, continuous borehole so the farmer in question every week sends his tanker there and fetch water and he keeps on producing. News has it that farmers are standing together in producing the same quality and cultivar of a product in various areas in the country in order to have a group of producers not lose their contract with a chain store. This is the kind of positive attitude that will carry South Africa through tough times. We believe strongly that the forthcoming season will bring the necessary rains where it is so badly needed. Flower farmers are also on the up as they captured markets elsewhere and can now again increase production. Positive thinking gets positive results! Ed.
GOLDEN WORDS • GOUE WOORDE
“The Lord foils the plans of the nations; he thwarts the purposes of the peoples. But the plans of the Lord stand firm forever, the purposes of His heart through all generations. Blessed is the nation whose God is the Lord.” Psalms 33:10-12 “Die Here vernietig die raad van die nasies, Hy verydel die gedagtes van die volke. Die raad van die Here bestaan vir ewig, die gedagtes van Sy hart van geslag tot geslag. Welgeluksalig is die nasie wie se God die Here is.” Psalm 33:10-12 S u b scrip t i o n / i n t e k e n i n g Online subs: Email to suzanne@axxess.co.za If you subscribe on-line, e-mail your deposit and address details to: magazine@axxess.co.za. More information from Suzannne Oosthuizen: 012-543 0880. Subscription form available on page 19.
v isi t u s at / b e s o e k o n s b y
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IMPORTANT MESSAGE TO ALL READERS, ADVERTISERS AND CORRESPONDENTS: CHANGE OF E-MAIL COMMUNICATION
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Front page: Ms Gill Gibson, greenhouse manager and Mr Thabo Motubatse of PSP show a sample of their potato seed production. See page 4.
Potato Seed Production in Greenhouses 4 Precision Agriculture: Drivers of Revolution 6 Ultrafine Bubbles and its Effect on Seed Germination 7 Rijk Zwaan – Investing in a healthy Future 8 De-clogging Disc Filters ensure Clean Water 10 New! the sweeper: Pepper Harvesting Robot Introduced 11 Climate control: Vents or Pad & Fan? 12 Wall Street of Fresh Produce not for faint of heart! 13 Rootstock Sub-Optimal Temperature Tolerance in Rootstocks and Scions of Grafted Tomato Plants 14 What Effect does Winter have on Greenhouse Production? 16 The Right Choice of Grow Media for your Hydroponics System 18 Scouting and Preventing White Flies to enter the Greenhouse 19 Subscription Form 19
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Potato Seed Production in Greenhouses
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Watering the plants by hand.
Potato Seed Production is currently producing around 2million mini tubers out of their 8 greenhouses, making them the second largest producer of potato mini-tubers in South Africa and has been providing these high-quality potato seeds to the potato seed industry since 1971, owing it all to the Mellet Family and their management team with a very loyal workers corps.
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otato Seed Production produces top quality potato seed of most open varieties and with prior permission from PBR owners, varieties with Plant Breeder Rights in SA. High quality, early generation potato seed are produced under the most rigidly controlled conditions and supplied as greenhouse tubers (G0 also referred to as mini tubers) to a wide range of areas in South Africa and abroad. Around 60% of the greenhouse yield is planted in our own fields to multiply to G1, G2, G3 and G4 for supplying further down the value chain to other seed and commercial potato growers.
PSP greenhouse staff scouting for diseases and pests.
Potato Seed Production green houses are climate-controlled and insect-proof greenhouses, which are strictly monitored to ensure that no infestation of plant material occurs. All growing media are sterilised before the commencement of planting. Generation 0 mini tubers have a zero tolerance of all relevant potato pathogens and viruses. They require regular inspections by a certification official of the South African Potato Certification Services at various stages. The PSP greenhouse team poses for a group picture. Ms Gill Gibson, greenhouse manager, appears on the right.
To page 5
Some of the greenhouses in which PSP produces potato seed.
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POTATO SEED PRODUCTION From page 6
5 with one of the exhibitors, Giant Light, and installed some lights in the greenhouses to lengthen our daylight hours. We are very positive about the first results and should be in a position to grow our production based on longer days, especially during the winter months. Potato Seed Production tries every year to deliver the best in the business. Not only do they strive to bring you the best Generation 0 mini tubers, but to deliver the best service, accommodation and excellence in every field. PSP
The PSP tunnels in a natural setting
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This is done during the pro duction cycle and finally testing of the tubers and/or leaf samples by Plantovita, the regulating laboratory in the industry, for all the relevant viruses and bacte ria before certification. Bore hole water used in the green houses is chlorinated to eliminate bacterial infection and is never recycled. Greenhouse production continues throughout the year and Generation 0 mini tubers produced in the greenhouses are all of superb quality with sizes between 4 and 200 grams. We are able to supply mini tubers all year round and cater for all production areas and seasons. Our eight greenhouses can Electronic managed climate control is used in the tunnels. produce up to three crops of mini tubers annually and cold storage facilities provide for year-round availability. As demand is ever increasing, customers are recommended to discuss their requirements with us at least 18 months in advance. Small orders can sometimes be accommodated in 10-12 months, depending on space and plantlet availability. Potato Seed Production has an extraordinary greenhouse team led by Ms Gill Gibson, our greenhouse manager. The Potato Seed Production’s greenhouse team consists of 18 people including Ms Gibson. We deploy 2 ladies to each greenhouse where they work hands on with the organizing and sanitising of the greenhouses assisting with the current 34 different varieties. Assisting them are our 3 handy gentlemen that helps them with maintenance and heavy duty work alongside one of our supervisors Mr Thabo Motubatse. Together they make sure that it is smooth sailing all year round to provide our customers with the best plant ready material on the date they want to plant in the fields. We are also constantly looking for ways to improve yield and size in the greenhouses. After attending the last undercover expo we met up
Precision Agriculture: Drivers of Revolution Precision agriculture is developing at an accelerating pace. Research companies expect a com pact annual growth rate (CAGR) of over 20% from 2018 until 2025. This estimate is based on known megatrends: population growth, tightening of agricultural regulation, deeper agronomical understanding, the expansion of agricultural knowledge and technological advancement.
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recision agriculture is developing at an accelerating pace. Research companies expect a compact annual growth rate (CAGR) of over 20% from 2018 until 2025. This estimate is based on known megatrends: population growth, tightening of agricultural regulation, deeper agronomical understanding, the expansion of agricultural knowledge and technological advancement. Improved artificial intelligence and new deep learning algorithms open the door to new services. It is easier to think of disruptive innovation driven change as a coherent process – a coalesced, one-front wave of technological breakthroughs and market responses. However, looking at it from a different perspective, showing this change process is, in fact, a multi-faceted advancement, made by vastly different players, with very different objectives. The motives of various stakeholders in digital/precision farming are quite different. Economic considerations, from which most decisions in modern agriculture are derived, demonstrate this: while commercial companies seek to maximize profits, growers also seek to maximize their revenues. Distribution of profits from precision agriculture among stakeholders is not expected to be equal. Input companies are expected to lose a considerable part of their profits due to the selective and differential use of chemicals and water where precision agriculture is practiced.
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The new digital agriculture services offered by the input companies are not expected to cover the difference. Farmers, on the other hand, are expected to benefit in two ways through the reduction in agricultural inputs and increase in crop yield and quality, which may support higher prices. Technology companies are expected to benefit from the move to precision agriculture: some will end up being acquired by bigger players, and some will exist independently, serving a new market. Agriculture regulatory bodies, representing public and ecological interests, are expected to benefit from increased sustainability, and this can be presented in economic terms. If there is no increase in revenues for input companies, then logically, they should shy away from entering precision agriculture altogether. But they do the opposite; they charge full speed into this new field, invest in start-ups, purchase technology, and offer new digital services. The grower, who stands to gain the most for these new technologies, often stalls, taking a conservative, cautious approach to adopting these new services. This conservatism on the growers’ side can be explained by the high risks involved. Many precision agriculture tools offer support for agricultural decisions: what to sow, when, how much to fertilize, how much to water, what to spray and when, where to do soil/leaf tissue sampling and how to interpret
the data. But the decisions that growers take impact on their livelihood and mistakes carry a high cost for the grower and their family. Growers will not put pivotal decisions at the hands of technology alone any time soon. Trusting a computer stands in stark contrast with the way they have managed their businesses all their lives, and the people they have trusted with the major decisions along the years. In comparison, technology companies stand to lose very little. In the worst case technology companies will abandon the technology and move on to the next one. For food companies, the risk lies in not adopting new technologies in time. Traceability along the food supply chain, to achieve better food quality and better food safety, to meet customer demand, can only be achieved by the use of technological tools. So, food companies risk losing future business to competitors which more quickly adopt the new tools. Getting experts and stakeholders from disparate fields to talk to one another, and find solutions to challenges faced by industry is, for the most part, conducive to innovation. In this respect, precision agriculture is absolutely all about innovation. However, this heterogeneity is a challenge when it comes to application. Technocrats view data as valuable in its own right. Growers do not necessarily share this view and only see actionable data as valuable if it leads to measurable results. Technology companies believe innovation is a sufficient reason for adoption. However, growers will only adopt new tools if their profits grow and – if this can be achieved without innovation – so be it. Claims of future benefits do not usually convince growers, especially if these claims are made by start-ups which may not exist in a year’s time. Regulators face other challenges: stricter regulation calling for less input is good as long as there is no food shortage. However, food shortages may flip any such decision. Even before that happens, stricter regulation raises costs. In low margin crops, this may lead to unprofitability which could lead, in turn, to less local supply and higher consumer prices. Any country facing food shortages will forego previously imposed regulations to avert the risk. Stricter regulation in agriculture is the right move today, but time will tell whether it is sustainable. Dissemination of agronomic knowledge has played a major role in raising agricultural productivity worldwide. It stands to reason that the next stage in the evolution of the sector comes from data, as witnessed in other sectors. However, not every new technology necessarily heralds a fundamental change in our lives. The internet brought about a multi-dimensional change, but arguably, not every gadget has brought about change, even if based on a novel technology. The same holds for agriculture: colourful satellite maps may not change all that much in agricultural practices. Auto-steering, deep learning algorithms and artificial intelligence, may, however, herald a new era in agriculture. Major role-players in providing precision agriculture solutions for the industry over years and leaders in specialty fertilizers, with well-known brands, such as the osmocote, committed them to provide growers plant nutrition solutions across the board. Digital agriculture is a revolution, which will affect us and our children. From where we stand, at the beginning of this change, it is difficult to predict its impact. All we know is that change is here and it will affect all humankind. By: Ziv Kohav, MBA – Precision Agriculture ICL
Ultrafine Bubbles and its effect on Seed Germination Seed germination is the process from seed to a sprout in which the metabolic machinery of a plant gets activated after a period of dormancy. A high seed germination percentage is important for vegetable production. Temperature, seed age, water and oxygen all have to be correct, to get high rates of seed germination.
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Ultrafine Bubbles are useful in accelerating the metabolism of living organisms, but the mechanism is not yet well understood. In a study, they investigated the production of reactive oxygen species (ROS) by Ultrafine Bubbles and the effect on seed germination. Micro bubbles are bubbles with a diameter ranging from several micrometers to about 100 μm. Ultra-fine bubbles are bubbles with a diameter of sub-micrometer. Ultrafine bubbles have an effect on living organisms and influence oxidation. Water containing ultrafine bubbles can accelerate the growth of plants, shellfish, and yeast. Furthermore, ultrafine bubbles are used to improve the oxidation effect. Ultrafine ozone bubbles can be used to remove pesticides residual from vegetables. They can inactivate micro-organisms and reduce organic material in wastewater. Apart from the oxidative capacities of ultrafine bubbles, it became apparent, during ultrafine bubble generation, the creation of exogenous reactive oxygen species (ROS) under the presence of strong acids or UV light.
Reactive oxygen species (ROS)
ROS are chemically reactive molecules containing oxygen; examples are peroxides, superoxide, hydroxyl radicals and a single oxygen. In nature, the formation of ROS is a by-product of oxygen metabolism. During environmental stress heat or UV, ROS levels can increase significantly, and this can lead to cell damage. We call this oxidative stress. Apart from the natural generation of ROS by the living organism itself, ROS can also be generated by sources outside the plant. Production of exogenous ROS can come from tobacco, smoke, drugs, xeno-biotics or radiation. It`s important to understand that ROS have both positive and negative impact on plants humans and animals.
Germination with H202 versus Ultrafine bubbles
Germination improvement of cereal plants like barley, wheat, and rice by adding H2O2 as a kind of ROS. When added in the right amount it`s not harmful to the seeds, it helps to loosen the cell wall which is an important signal function to start the growing process of the plant. In the study, seeds were germinated under five different conditions, with distilled water, three different concentrations of hydrogen peroxide and ultrafine bubbles. To avoid the influence of dissolved oxygen (DO) the levels of water were adjusted to be the same as that of distilled water. The conclusion of the study was that adding H2O2 stimulated the ROS production in barley seeds and after 17 hours of germination the seeds in ultrafine bubble water had a higher germination rate than all those submerged in the different H2O2 solutions.
Cause of ROS in water
Reactive oxygen species are often seen as damaging compounds for the development of cancer and other diseases. On the other hand, when no reactive oxygen species are present a seed will not germinate. Therefore the concept of "oxidative window of germination" is introduced indicating that only successful germination will take place with the correct amount of reactive oxygen species. More research is required to fully understand the mechanism of ultrafine bubbles and the physiological promotional effects. The reason why ultrafine bubbles are more successful than H2O2 could be that during storage the
Germination of seed is influenced by ultra-fine bubbles. This study could also be of importance to the vegetable producer.
bubble concentration gradually reduces it could be that the disappearance of ultrafine bubble causes a constant production of ROS in the water. Source: ACS Sustainable Chemistry Engineering.
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Ultrafine bubbles
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he process of germination is not only important for farmers to grow new plants, it is also important in the food and beverage industry where the germination process is also been used but then it is called malting. All whiskey and beer is produced via malting. The importance here is not the germination but the change from the starch in the seed in to sugars.
Rijk Zwaan - Investing in a healthy future With approximately 30% of turnover invested in Research and Development, Rijk Zwaan really commits in developing vegetable varieties for the future.
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he latest varieties Rijk Zwaan has to offer were showcased from 18 June to 6 July at demo fields in Fijnaart, Holland. Rijk Zwaan welcomed a large number of visitors from all over the world at this annual demo that is aimed at everyone who is involved in choosing varieties – not only growers, but also processing companies, industry partners, traders and retailers. A wide variety of crops were presented with the focus being on the broad and innovative assortment of lettuce and spinach varieties. Other crops included cabbage, cauliflower, broccoli, corn salad, Swiss chard, endive, radish, celery, celeriac, Baby marrow and fennel. There was a lot of interest in the Knox™ and Knox core™ trait in lettuce, which slows the discolouration of cut surfaces and the core. The Knox™ trait is a major advantage for processors and the Knox-core™ trait is a huge benefit for the fresh market. In the below image the clear advantage of the Knox-core™ could be visually seen on the Iceberg variety containing this valuable trait on the right.
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With the 56 Iceberg varieties, 286 lettuce varieties of different types and 70 Baby Spinach varieties in this Demo, Rijk Zwaan showed why they are the preferred partner of so many leading Lettuce and Baby leaf producing, processing and marketing companies’ worldwide. Keeping track of all the varieties at such a large demo could be difficult, but Rijk Zwaan’s innovation does not stop at their varieties. All visitors installed the Partner RZ app. This enables you to scan the QR codes of your favourite varieties and immediately see each variety’s specific traits. Comments and notes can easily be added. To make it more user friendly, the complete product catalogue of the demo was available on the app, making it easy to share via e-mail or WhatsApp. Planting different vegetables and showing them to different people sounds easy right? Actually, it couldn’t be further from the truth, Gerhard Smit, MD of Rijk Zwaan SA notes. “The demo is only hosted for a certain period of time. Many visitors throughout the world visit these open fields and they want to see something spectacular. Very careful planning goes into making sure that the plants are ready for their big showcase and planning and execution needs to be
adapted constantly to the weather.” How does Rijk Zwaan develop such an exten sive range of varieties? Rijk Zwaan always thinks long term, and therefore it needs a constant flow of information from the entire value chain, Gerhard explains. The below diagram indicates the never-ending process in pursuit of the perfect variety. The first crops for the autumn demo have already been sown and planted. This demo will take place during September and October. Gerhard concludes, “Just like our local farmers always planning for their next planting or harvest, our colleagues in Holland are already thinking about the next summer demo fields and what varieties our farmers will be planting in the near future”.
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De-clogging disc filters ensure clean water
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he main objective of installing filtration systems both on a plot and headland level, as a part of the communal system, is the protection of all the elements that make up the system. The installation of filter equipment enables the following:
• Improvements of hydraulic performance in the lines. • Reduction in maintenance work for the control elements, protection and measurements installed in the water distribution networks. • Reduction in the necessary maintenance for the safety filters on a plot level. • Elimination of particles, which are big enough to produce clogging in micro-irrigation systems.
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For the suitable selection of a filtration system the producer needs to know the origin and type of clogging that can occur:
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TYPES OF CLOGGING According to the size of particles that can cause clogging, these can be classified as follows: • Particles with a direct clogging capacity due to their size can block certain installation elements. • Clogging caused by large particles can be prevented by installing filtration equipment that ensures optimal water quality. • Particles with no clogging capacity (not initially at least) may sometimes exist if conditions are favourable. Clogging can also be produced by very fine particles that go through the filters and under certain conditions (prolonged presence of water in the interior of the lines and variations in the water circulation speed) can form larger sized particles. To prevent this, filter dimensions should be suitable to ensure that the filter grade is correct. On the other hand, according to the origin of the matter causing the clogging, it can be caused by physical, chemical or biological originated particles: • Physical originated particles Produced by particles of inorganic nature. Two different types: • Internal Clogging. Caused by physical matter (sand, silt, clay) present in the water source destined for irrigation. • External clogging. Produced by matter that is introduced from the exterior into the interior of the system through: line joints, air relief valves, cracks in the distribution network, emitters in negative pressure conditions, etc… • Chemical originated particles
A de-clogging filtration system ensures even growth and quality produce.
be carried out, the intrinsic characteristics of each type of filter, the filtration system safety and maintenance throughout its useful lifespan. The number of filters and the size, with the chosen filtration system and necessary filter grade, must be suitable to cover the requirements in periods of maximum demand. One must take into account that these periods normally coincide with the lowest levels of water quality. For this reason, and before the decision of different filtration systems, the producer must check whether the chosen system is appropriate for his installation system and complies with the following characteristics: 1. High safety filter quality faced with variable conditions of:
- Water quality: types of solids in suspension. - Circular water flow. - Work pressure. - Existing differential pressure. - Frequency of maintenance work.
Caused by precipitation in the interior of the installation containing fertilizers or substances dissolved in the irrigation water that passed through the filters. There are also two types:
2. Efficiency of backwash system in the automatic equipment.
• Direct chemical clogging
5. Easy maintenance work.
3. Minimum water use possible with highly efficient filtering and cleaning. 4. Long-term stability of properties. To page 11
• Those generated by precipitate in-situ. • Indirect chemical clogging. Clogging generated by particles which come from the detachment of chemical precipitates generated above the point where the clogging has finally taken place. Their behaviour and treatment are the same as for inorganic particles. • Biological origin particles caused by organisms or organic remains. These can be classified in two groups: • Inorganic particles with no proliferation capacity. Vegetable and animal organic remains in suspension in the water flow. Their behaviour and treatment is the same as for inorganic particles. • Particles with proliferation capacity. Organisms present in the water (small insects, algae, micro-organisms…) that initially do not have direct clogging capacity but it is acquired due to their proliferation (multiplication or development) inside the flow and distribution networks. When choosing between different filtration systems, one should evaluate the water flow, properties of the water to be filtered and the quality required; as well as subsequent cleaning operations and maintenance that will have to
DISC FILTRATION SYSTEM
Microscopic view of disc channels 130 micron Helix delay element for silting
Adapts to function under various water conditions. Faced with changing conditions in water quality or in the use and destination of the filtered water, through grooved discs the filtration system can allow for the change of the filtration grade easily, quickly and economically, carrying out this operation without using tools.
The disc filtration systems provide the solution to problems that can come up in the distribution network due to solids that the water carries in suspension. The main features that highlight these filters are visible in the graphic illustration. These discs retain all types of particles, no matter their nature (organic or inorganic), as long as their size is greater than the filter grade.
Maximum safety is ensured throughout its useful lifespan. Unlike other filtration systems, this system does not reduce the quality of filtration even when working under pressure differences at all times, or handled improperly, or the duration of use.
These carry out filtration in depth. Not just the particles that have a greater size than the filter grade are retained by the filter element, but a high percentage of smaller sized particles can also retained. If a particle that has not been trapped on the surface enters the disc channel, the probability of it being retained depends on the following: • Size and form of the particle in relation to the dimensions of the channel: transversal area (directly linked to the filter grade) and its length. • Nature of the particle. • Existence of other particles already retained
inside the channel that act as an obstacle for the rest and provide retention. In other words, an increase in efficiency is achieved as the number of particles retained rises (pressure differential increases), therefore, we can assure that as the grade of silting increases there is an increase in the quality of the filtration. Resistance of the filtering element under high differential pressures levels, without causing its breakage. This is due to the high resistance carried by the disc set that is compressed and housed in the interior structure.
Reduced water consumption during the backwash process compared to other filtration systems.
Detail of the HELICAL ELEMENT silting delayer situated in the base of the disc cartridge, creating a helical effect in the water that takes the particles away from the filter element, thus, noticeably delaying its silting.
One must take into account that it is essential to know the “useful capacity” of the filter when purchasing filtering elements of the same nature and it is important to consider the existence of auxiliary elements that improve the effectiveness and efficiency equal to the surface use. These elements are the so-called “silting delayers”, that are able to reduce the frequency with which cleaning has to be carried out, whether it is manual or automatic. Source: Greenzone
new! the sweeper: pepper harvesting robot introduced Robots are on us! On Wednesday, July 4th the first live demonstration of the SWEEPER pepper harvesting robot took place. This demonstration was given at the commercial greenhouse "De Tuindershoek" in IJsselmuiden, one of the partners in this international research project. The BU Greenhouse Horticulture of Wageningen University & Research coordinates the project in which partners from Sweden, Israel and Belgium also participated.
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he SWEEPER robot is the first sweet pepper harvesting robot in the world demonstrated in a commercial greenhouse. SWEEPER has been concentrating on harvesting peppers for the past three years, with 1.3 million tonnes being produced annually in Europe. The consortium expects that the outcome of their research will lead to an international market introduction of the robot within a few years. SWEEPER is a partnership between Wageningen University & Research, pepper grower De Tuindershoek BV, Umea University in Sweden, Ben-Gurion University in Israel and the Research Station for Vegetable Cultivation and Bogaerts Greenhouse Logistics from Belgium. WUR This is just one more step towards labour-saving costs and accurate selection before picking. There is also the benefit of less handling of the product. An important consideration for the fresh produce farmer (Ed).
The newly developed SWEEPER robot picking sweet peppers in a greenhouse. (Pic: WUR)
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FILTER PHASE IN THE DISC FILTRATION SYSTEM
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DE-CLOGGING DISC FILTERS From page 10
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Climate control: vents or pad & fan?
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South Africa soon will be experiencing summer and with it soaring temperatures in some places where climate control for optimal production for the coming season is high on the agenda in every greenhouse operation.
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entilation in greenhouses is essential and it has decisive effects on crop results. Increases in temperature and humidity levels damage the yield and affect the quality of the crops. In many cases, higher temperatures and increased humidity are also a burden on greenhouse workers, which indirectly leads to a decline in output and greenhouse profitability. Ventilation, either on the walls of the greenhouse or along the structure's rooftop, serves as natural ventilation and hot, internal air is expelled through these air vents. Due to low levels of internal air pressure and the effect of external winds, cold air is forced into the greenhouse. Air vents can be controlled either manually or automatically. Natural ventilation in greenhouses is effective only to a certain length of the structure. What measures can be taken in greenhouses that extend over an extremely large area? This is particularly true when growing tomatoes and cucumbers. The height of the trellised vegetables disrupts the flow of air within the greenhouse.
A number of solutions have been developed to deal with the situation: Air Vents along the Rooftop – "The Natural Solution" One of the solutions currently available on the market is the installation of air vents along the greenhouse's rooftop. These vents enable the heat and humidity that have accumulated inside the greenhouse to be expelled naturally. The advantage of this solution is based on the fact that heat rises and the opening of the roof structure enables the heat to be expelled from the structure
without any kind of intervention. There are advantages of natural ventilation: • Lower installation and maintenance costs • No need for electricity • Allows for longer gutter front lengths along the greenhouse Though there are certain disadvantages in this system: • Low to almost no ability to control and determine internal climate conditions (unless you go to the expense of an electronic controlled automated system at extra cost) To page 13
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CLIMATE CONTROL From page 12
• High dependency on external climate conditions It is important to remember that when choosing the natural ventilation system, there are technological means for assisting and increasing the internal air flow, such as: 60cm air circulators, or as an alternative, circulators combined with a thermal screen. The addition of these systems is likely to lead to better results. Clearly, results are also influenced by external weather conditions and the geographic location of the crops.
Pad and Fan System This solution requires the installation of a ventilation system within the greenhouse. The system enables the grower to achieve ideal internal climate conditions while addressing the type of crop, external climate conditions and the size of the structure. While taking these three factors into consideration, the following systems are required for best results: fans, air circulators, a humid pad, screens and additional equipment suited specifically to the needs of the grower and the particular crop. Not only does this solution enable proper ventilation of the greenhouse, it also creates optimal conditions for producing a larger and higher quality yield. Advantages of Pad and Fan: • Full command and control over internal climate conditions • Better annual results without dependency on external conditions Disadvantages of Pad and Fan: • Higher costs in comparison to Natural Ventilation • Dependency on the supply of electricity • Shorter gutter front lengths (a maximum of 36 meters long) In conclusion, it is generally advised by greenhouse equipment technologists to be acutely aware of the site, district’s temperature pattern over past years, the type of crop, the security of a sustainable power source and where in the country the producer wishes to set up his/her production site. Source: Inputs by Shimon Valensi and the editor.
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U N D E R C O V E R F A R M I N G
Rootstock Sub-Optimal Temperature Tolerance in Rootstocks and Scions of Grafted Tomato Plants
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Grafting of elite cultivars onto tolerant rootstocks is an advanced strategy to increase tomato tole rance to sub-optimal temperature. However, a detailed understanding of adaptive mechanisms to sub-optimal temperature in rootstocks and scions of grafting combinations on a physiological and molecular level is lacking.
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or instance, a commercial cultivar Kommeet was grafted either onto ‘Moneymaker’ (sensitive) or onto the line accession LA 1777 of Solanum habrochaites (tolerant). Grafted plants were grown in a NFT-system at either optimal (25°C) or sub-optimal (15°C) temperatures in the root environment with optimal air temperature (25°C) for 22 days. Grafting onto the differently tolerant rootstocks caused differences in shoot fresh and dry weight, total leaf area and dry matter content of roots, in stomatal conductance and intercellular CO2 and guaiacol peroxidase activity but not in net photosynthesis, sugar, starch and amino acid content, lipid peroxidation and antioxidant enzyme activity. In leaves, comparative transcriptome analysis identified 361 differentially expressed genes (DEG) responding to sub-optimal root temperature when ‘Kommeet’ was grafted onto the sensitive but not when grafted onto the tolerant rootstock. 1509 and 2036 DEG responding to sub-optimal temperature was identified in LA 1777 and ‘Moneymaker’ rootstocks, respectively. In tolerant rootstocks down-regulated genes were enriched in main stressresponsive functional categories and up-regulated genes in cellulose synthesis suggesting that cellulose synthesis may be one of the main adaptation mechanisms to long-term sub-optimal temperature. Downregulated genes of the sensitive rootstock showed a similar response, but functional categories of up-regulated genes pointed to induced stress responses. Rootstocks of the sensitive cultivar Moneymaker showed in addition an enrichment of up-regulated genes in the functional categories fatty acid
desaturation, phenylpropanoids, biotic stress, cytochrome P450 and protein degradation, indicating that the sensitive cultivar showed more transcriptional adaptation to low temperature than the tolerant cultivar To page 15
Rootstock Sub-Optimal Temperature From page 14
The performance of a grafted plant under suboptimal temperature conditions is specific for each rootstock/scion combination, because lowtemperature tolerance is a complex secondary trait depending on many primary traits (e.g., root and leaf morphology, plant hormones, ROS scavenging compounds, etc.) operating in both the roots and shoots.
that did not show these changes. Mainly defence-related genes were highly differentially expressed between the tolerant and sensitive rootstock genotypes under sub-optimal temperature in the root environment. These results provide new insights into the molecular mechanisms of long-term sub-optimal temperature tolerance of tomato. A commonly encountered abiotic stress for cold-sensitive vegetables that restricts their yield potential is the exposure to sub-optimal temperatures, i.e., cultivation above the minimum growth temperature range of 8–12°C instead of at the optimum temperature range of 18–27°C. Suboptimal temperatures of 8–18°C also negatively affect tomato growth and development due to shorter internodes that restrict plant height, retardation of leaf expansion, reduction of leaf number and total leaf fresh mass and increased dry matter content and thickness of leaves due to increased starch storage. It was found that sub-optimal temperature induces changes in root phyto hormone production. This has an impact on root-to-shoot hormone signalling resulting in reduced plant productivity. In addition, temperatures below optimum impair cell membrane fluidity and increase permeability, resulting in ion leakage while intra- and extracellular water and nutrient movement are inhibited, reactive oxygen species (ROS) are generated, photosynthesis may be restricted, and finally yield is reduced. Different cultivated tomato varieties may exhibit significant differences in their responses to sub-optimal temperature. An increase in the tolerance of tomato plants to sub-optimal temperature could considerably reduce the energy cost for growth in heated greenhouses. Although traditional breeding over the last 30 years resulted in cultivars with twofold improved energy efficiency as a result of increased yield, there is now also a need to reduce the absolute amount of energy input. A further successful cultivation of tomato in the field and in unheated greenhouses under lower temperatures requires either the breeding of new cultivars that are better adapted to low temperature or an increase in the tolerance of tomato to sub-optimal temperature aimed to extend the growing period. However, due to low genetic diversity within the cultivated tomato species Solanum lycopersicum L. and reduced pollen fertility in interspecific tomato hybrids, breeding of high-yielding tomato cultivars with enhanced tolerance to sub-optimal temperature has not been successful so far.
The results of several tests provide new insights into the molecular mechanisms underlying the sub-optimal temperature tolerance of the wild tomato S. habrochaites. This knowledge can be utilized to establish biomarkers to screen not only wild tomato genotypes serving as rootstocks but also rootstock/scion combinations that are likely to be tolerant to suboptimal temperature. Schwarz et al. Ed.
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It originates from an altitude of about 3.200 m where an adaptation to low temperatures can be expected. The superiority of this cultivar is due to the presence of adaptive mechanisms to alleviate cell damage and to reproduce under sub-optimal temperature.
U N D E R C O V E R F A R M I N G
An alternative strategy to enhance the tolerance of elite tomato hybrids to sub-optimal temperature is to graft them onto rootstocks that are compatible with the cultivated species and tolerant to suboptimal temperature. Such rootstocks might be interspecific hybrids of S. lycopersicum with accessions of cold-tolerant wild tomato species, such as S. habrochaites. The latter species is of particular interest as a potential source of germ plasm to widen the genetic variation for low temperature tolerance of cultivated tomato.
What effect does winter have on greenhouse production? Often people ask the question of what effect extra cold temperatures have on undercover farming. Generally, in South Africa the only effect is (where produce are hydroponically grown, for a start) that of higher production input cost because of heating. With electricity and gas prices going through the ceiling, producers have to bite the bullet to keep production at an even keel.
U N D E R C O V E R F A R M I N G
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eeing fresh produce on the grocery store shelves throughout winter is nothing new – our greenhouse producers have been making it happen for years. What is new, however, is the increase in technical applications in both structure, inventions like screen systems and of course, electronic devices. Some farmers use insulated tanks to pump outflow water from the greenhouse to the tank as it maintains a much higher temperature as that in the reservoir. This means the stored water needs less energy to be heated up to the required temperature to heat the greenhouses. The morphology of roots of plants grown in greenhouses is as such that it does not produce well if temperature at the roots decreases below 16-18°C. This has been tested and confirmed over and over. Therefore it is imperative to heat the surroundings of the roots to an amiable level to expect flourishing of the plant and thus it will offer optimal production during winter. In winter rainfall areas like the Western, Southern and Eastern Cape, greenhouse structures provide farmers with an attractive environment protected from snow, frost, wind, and excessive rain, and allow the grower to control the humidity, moisture, and temperature.
Undercover farming The first known greenhouses were designed by the Roman Emperor Tiberius (42 BC – 37 AD), explains John Perlin, author of Let it Shine: The 6,000 Year History of Solar Energy. Tiberius had “a penchant for cucumbers,” says Perlin, and had special carts of soil built to be wheeled into the sun and covered to retain the heat, keeping his cucumber plants producing through winter. Although the use of glass in winter agriculture more or less disappeared through the Middle Ages, interest in covered growing spaces rebounded around the 15th Century. This type of growing, though effective, was severely labour intensive. And covering large spaces with glass panes was simply beyond the budget of most small farmers. So although many elaborate greenhouses were built from the 15th Century to the early 20th Century, most weren’t within reach of the average grower. Everything about winter production changed when polyethylene plastic came along. By the 1960s plastic for greenhouses was widely available. Labour went down, so the profitability of winter farming went up. However, while these large plastic structures solved certain problems, they created new ones.
Under cover crops What most greenhouses do if left unmanaged is not create a perfect microclimate; rather they create a desert. They concentrate heat while preventing moisture from penetrating, so although this covering helps protect from wind, snow, and excess rain, irrigation becomes essential. Once you bring water into these houses, however, you create humidity, excesses of which can lead to fungal diseases on your crops.
The worst case scenario! Fortunately in South Africa few undercover farmers are situated in areas where this can happen.
A typical gas heating installation with insulated tank to keep the outflow water at its temperature in order to only use minimal energy to heat to the required temperature. At left is an enclosed reservoir under roof.
Sealing out the wind also seals out the airflow, further adding to disease susceptibility, damaging pollination, and encouraging pest problems like aphids. Then, of course, you still have to worry about extreme cold killing your plants. Add to these problems the fairly prohibitive cost of building the structure itself, and it just wasn’t worth it for most farmers to expend the energy to grow food in winter.
Greenhouse boom Then, late in the last century, things started to change. Growers persisted - some annually visit Holland, Spain and other countries to gain first-hand knowledge, paving the way for a dramatic increase in farmers growing under cover. Designs were revised, and technology rose to meet the needs of winter farmers. Now, protected culture is a much different, and more approachable, story. The improvements in the flexible plastic itself, sometimes called greenhouse film, has likewise been crucial to the shift. Not only is the plastic now made to resist degradation from ultraviolet radiation, but many films now contain anti-condensation coatings that help spread the water out, encouraging better light penetration while preventing drips. Manufacturers have also started to manipulate the film technology to take better advantage of the greenhouse effect, allowing more light to come in but less heat to escape. Latest designs in plastic offer extra-long life under average conditions.
Electronic management The Internet of Things is currently the major management tool that enables the greenhouse operator to remotely monitor elements such as humidity and temperature from their homes or via cell phones. Not so long ago (although time flies!) a story was published in Undercover Farming of a cucumber producer that admitted he sets his alarm for every two hours during night (yes, in winter too!) just to check on his night manager that all is well. Now he sleeps soundly as if anything goes out of order anywhere in any of the greenhouses or general system, it will give him a call. Ultimately, farming is a job limited by available sunlight and heat. Innovations like those described above however, stretch those resources for farmers, opening up more opportunities for income, but also for levelling out the workload so as not to be so dependent on summer production. That is all the more reason for farming undercover in South Africa. Ed
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U N D E R C O V E R F A R M I N G
The right choice of grow media for your hydroponics system Soilless media of various kinds and mixtures of various soilless media have been used in greenhouses for several years. Commercial media mixes are available, but most of the basic ingredients are also available separately.
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oilless media is isolated from the ground so that diseases and insects are not transferred because of contact. The media is therefore used in containers, and can be used for a period of time and then replaced with new, fresh media. Different containers characterize the different production systems within this category. They include upright bags that can be filled with a number of different media or media mixes. Rockwool slabs are rather characteristic of the type of bonded material they contain. Foam rubber slabs are similar in appearance to rockwool from the outside. Horizontal bags are filled with perlite, or any number of different soilless mixes. Long troughs, almost the length of the greenhouse, are used to house organic soilless mixes where microbial activity within the media will be relied upon extensively in the provision of the fertilizer to the plants. The fertigation and drainage of these systems are all somewhat similar. Differences in the media will require minor adjustments in the frequency and amounts of solution to be applied.
Inorganic Media Inorganic media – defined as media that do not interact with fertilizer ingredients supplied to them - include material like sand, gravel, rockwool, perlite, LECA. These materials will not support microbial growth. Vermiculite is the exception. It is expanded mica and has many chemically reactive sites. This allows it to interact with and hang onto or tie up fertilizer ingredients supplied to it. Although this may have some advantages for growers, this characteristic eliminates it as a media in a purely hydroponic system. Conversely, in organic media, microbes break down organic material and receive energy and nutrition from the process. In a strictly hydroponics system, the nutrient needs of the plant are supplied to it in a water solution. The fertilizer ingredients all need to be water soluble and available to the plant in the form supplied. Any media utilized in the system does not chemically interact with the fertilizer solution to any appreciable extent. Sand and gravel are usually not used as media in many different types of hydroponic systems within the continental United States. Although they are relatively inexpensive, they are heavy and would need to be heated to high temperatures or otherwise treated to assure the absence of disease organisms. They have only a barely functional air-water availability relationship. Horticultural rockwool, perlite and LECA (Light Expanded Clay Aggregate) are all processed or manufactured at sufficiently high temperatures to eliminate any living substance within them. This is one of the attractions for these substances as media or media components in hydroponic and other soilless production systems. Perlite is created through a heat process. When heated, it is popped in a similar fashion to the way popcorn is popped. The individual perls are full of small air spaces that can also hold water. Water can be wicked up to a height of about 8 inches in perlite. The availability of both water and oxygen in the perlite media makes it a very good environment for the growth and development of plant roots. Horticultural rockwool is manufactured with characteristics that provide an ideal air-water relationship also. The basalt rock from which it is made is ground, heated and dropped onto a spinning disk. The hot particle cools into a fibre as it leaves the spinning disk. At that point, the fibre could be part of an insulation pad or it could become horticultural rockwool. The specific resin used and the density of the fibres is what creates a product with the properties that support the environment needed for root growth and plant development. Although rockwool is available as a loose product, it is often used in the greenhouse in the form of a plastic-wrapped slab. The slab has a limited usable life because the structure breaks down with time - when the structure breaks down, the airwater relationship changes. The availability of oxygen in the media decreases as the structure of the media breaks down.
Organic Media Based Systems Organic production systems include certifiably “Organic” systems and systems consisting of recycled plant material. These types of systems are more complex than the hydroponic systems, involving a series of processes within the media. The organic media in the system harbour micro-organisms that will break down the organic matter itself, and sometimes also break down fertilizer ingredients that are supplied to the system. The fertilizer ingredients from the organic matter are made available to plants in the system by the activity of the micro-organisms living in the media.
At the same time, the micro-organisms themselves will use some of the fertilizer supplied to the system. A system like this is more difficult to use, requiring monitoring of the various simultaneous processes. The observant grower will gain valuable experience over time. Within the complex organic system, micro-organisms break down organic molecules during the decomposition process. Ingredients being provided to the plants growing in the media will also be taken and used by the microorganisms themselves. The grower needs to realize that both micro-organisms and plants need to be fed some fertilizer ingredients. As the micro-organisms break down the organic media, certain fertilizer ingredients can be released from it. Some media can release toxic quantities of one or more micronutrients during at least one stage of the decomposition process. This needs to be accounted for in the fertilizer program. Certifiably “Organic” systems may contain many – and more - of the ingredients mentioned here. Certain ingredients are prohibited in “certified” systems. Due to its complexity, we will refrain from fully exploring the Certifiable “Organic” System in this article. The media used on an organic system is often recycled plant material from other agricultural or forestry production or processing operations. A major exception to this is the use of sphagnum peat - a natural deposit of plant material that occurred in ancient bogs. Conservation concerns and decreasing availability have reduced the reliance on sphagnum peat as a component in many soilless plant production mixes. Alternative materials are becoming more readily available. Other materials used in organic systems include sawdust, pine bark, rice hulls, ground corncobs, ground peanut shells, and coco coir. These are used alone or in combination with each other and with aggregates such as perlite or vermiculite. The media used often depends on the local availability of the component or components. Rice hulls, for example, are more commonly used in or near rice producing areas. The different organic components decompose at different rates. Ground corncobs and rice hulls decompose more quickly than pine bark and coco coir. The decomposed or partially decomposed media will consist of smaller particles that will settle closer together and can restrict the availability of oxygen to the roots of plants growing in the media. Often, coco coir, pine bark or an aggregate such as perlite is used in the soilless mix to provide aeration after some of the other components have partially or even extensively decomposed. Organic media and organic media mixes have been used in two different ways with respect to the decomposition process within them. In the first, organic media have been used as a substitute for aggregates in an otherwise hydroponics system. In these instances, the fertilizer supplied to the system is a completely soluble and plant-available preparation that does not need to be processed by the media. The decomposition within the media is accepted as part of the nature of the system and is adjusted for in the production process. Rice hulls, for example, release levels of manganese during the early stages of decomposition that are toxic to tomatoes. Many growers, therefore, wet the rice hulls down and let the decomposition begin and continue for a couple weeks so that the manganeseproducing stage of decomposition has passed before transplanting the tomato plants into the media. When used in this type of system, where the fertilizers are completely soluble and readily available to the plant roots, the volume of organic media used per plant is similar to the aggregate media per plant because the decomposition process within it is not being depended upon by the plant production system. In the second type of organic system, organic media components are used with less soluble and insoluble fertilizer ingredients. In this instance, the fertilizer To page 19
Scouting and Preventing white flies to enter the greenhouse Although the colder temperatures are still felt at night, we notice some trees starting to wake up out of their winter sleep – especially on the Highveld areas where temperatures are slowly increasing. This should be a wake-up call for undercover farmers as whitefly might strike suddenly.
Note: White fly is found on the underside of the leaf
What must we keep in mind when deciding on a control strategy for white flies?
1 The life cycle is very short, and the reproductive rate is very high. This created an ideal situation for the development of resistance. Strategy: Use insecticides with different modes of action in a control program. 2 As mentioned, these insects feed on plant juices which they suck from the host plant. Strategy: Implement a registered systemic insecticide which contains imidacloprid or acetamiprid as one of the products in your program. 3 The white fly has some natural enemies, which can aid in the control of the pest. Minute wasps will lay their eggs in the white fly nymphs, thus using the white fly nymph as a food source. Strategy: select insecticides which have a limited effect on these natural enemies. 4 The white fly inhabits the undersides of the leaf surfaces. Strategy: when using conventional, non-systemic insecticides, the undersides of the leaves need to be sprayed, or no results will be obtained. There are products on the market of well-known brands that is extremely efficient against the immature stages of the white fly, but has no effect on the adults. For the best results spray two applications, 7 –14 days apart. Remember, the adults will still be around after the first application – they are not controlled by a single application at immature stage only. The greenhouse staff must be alerted and informed what and where to look for white fly on the underside of your crop’s leaves. At the first sight of white fly, take immediate action – you may save the majority of your crop! JS
GROW MEDIA From page 18
ingredients are processed and made available to the plants by the microorganisms living on and decomposing the organic media. This is the type of system that can be certified as “Organic” when certain allowable components are used. For these types of systems, larger media volumes per plant are needed since the fertilization is made available to the plants through microbial decomposition of the media itself. The larger media volumes provide for more organisms and more processing of fertilizer ingredients per plant. Plants growing in such systems will need to develop a more extensive root system because some of the needed fertilizer ingredients may be scarcer or more slowly available.
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To remedy this, at least some of the insoluble or slightly soluble fertilizer ingredients can be mixed with the media before the plants are transplanted. Finely ground, insoluble fertilizer ingredients can also be supplied in suspension through irrigation drip tape. This can be supplied to the plants at the same time water is supplied each day. In closing, the solution to finding the right grow medium for your system is to obtain advice from your seedling supplier and to talk to growers of the particular crop you intend to grow. The ideal grow medium is of much importance as this will establish to a large extent your success with growing plants of equal standing and production. JS
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U N D E R C O V E R F A R M I N G
White fly
present in large numbers, due to the removal of the plant juices, but these insects may also transmit viral diseases from plant to plant, much in the same manner as female mosquitoes distribute the malaria parasites.
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f we need to successfully control a pest, we need to understand the life cycle and the general behavior of such a pest. Let’s have a look at the white fly. It is important to understand that this insect is certainly not related to a fly in any way; in fact they are closely related to aphids and scales. This is important to understand, because insecticides that work for the control of flies may be ineffective against white flies. White flies and aphids feed by sucking the plant juices from the host plants using sophisticated mouth parts adapted to act like a straw. A mature female is approximately 1 mm long, and lays up to 100 minute, elongated stalked eggs on the underside of the host plant. There emerging nymphs will moult four times before the adult stage. Warm and humid weather favours the quick development of the insect, and the life cycle may be completed in as little as 14 days. White flies damage the plants when they are
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