DROPSA

Protecting the fruits of farmers’ labour Insect pests and pathogens represent a significant threat to the EU fruit industry, destroying crops and causing significant financial losses. The Dropsa project has been developing a cost-effective, integrated approach to pest management that will help protect crops and boost the European fruit industry, as Dr Neil Audsley explains

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A type of fruit fly, Drosophila suzukii was

Drosophila suzukii

first recorded in Europe (Italy and Spain) in 2008, and it has since had a significant impact on soft fruit production. Drosophila suzukii is extremely difficult to control with pesticides, as Doctor Neil Audsley, the coordinator of the Dropsa project, explains.

“It lays its eggs and larvae develop inside the fruit, causing the fruit to rot. Furthermore, the harvest to market interval, when pesticides are not applied, coincides with the time when the fly infests the fruit,” he outlines. The major aim of the Dropsa project was to improve the management and control of new and emerging pests like D. suzukii, as well as specific pathogens that affect fruit production. “We’ve also been working on three pathogens, Pseudomonas syringae pv. actinidiae (Psa) on kiwi fruit and Xanthomonas species on soft and stone fruits. These pests and pathogens normally arrive on imported fruit or plants, then spread more widely.”

Many different pests and pathogens have arrived on new shores in this way, and more could potentially be introduced into Europe via the fruit trade, as vast quantities of goods cross borders every day. Dropsa has investigated the pathways of introduction of different pests and pathogens, which will provide a basis for the development of preventative strategies. “The pathways and the risks involved with the trade of certain fruits and what would be carried by those fruits have been reviewed. An alert list for soft fruits, as well as apples, table grapes, oranges and mandarins, has been created to try and identify the pests that could potentially be introduced,” says Dr Audsley.

Since its arrival in Europe D. suzukii has spread across the continent, causing significant financial losses to fruit growers.

In Europe D. suzukii is not regulated by natural factors - unlike in its region of

has been spent looking into this,” explains Dr Audsley. “Drosophila suzukii for example is quite cold-tolerant. It breeds best at 20-25 degrees, but it will survive at low temperatures (-5°C).”

A major problem with this particular

A major problem with this particular pest is that it has a very large host range. It attacks not only horticultural crops, such as strawberries, raspberries and other soft fruits, but also a lot of wild fruits origin - hence populations are unchecked and can grow rapidly, causing serious problems. “You need to understand the ecology and biology of the pest to help identify means to control it. A lot of time Project coordinator Dr. Neil Audsley attending to a Drosophila suzukii monitoring trap.

pest is that it has a very large host range.

It attacks not only horticultural crops, such as strawberries, raspberries and other soft fruits, but also a lot of wild fruits. “It survives in woodland and hedgerows where there’s food present. When crops start to ripen, it migrates into the crop. You can’t just indiscriminately spray pesticide along hedgerows and in woodlands,” points out Dr Audsley. Given this background, an area wide control strategy, such as biological control, is required. “We’ve been investigating parasitic wasps that attack D. suzukii, both those that are native to Europe and also parasitoids from Asia, where D. suzukii originates. These parasitoids may help to keep the pest in check in the region of origin,” outlines Dr Audsley. “However, a non-native parasitoid from Japan cannot be released in Europe without authorisation to do so – it’s a bit like introducing another pest.”

The introduction of an exotic biological control agent may affect native species and disrupt the local eco-system, so it’s essential to understand its wider impact before it can be introduced. ”Exotic

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parasitoids have been identified which show potential in controlling this pest in the laboratory,” he says. “The work on these parasitoids will continue over the longer term, in the hope that permission to release them as a means of controlling D. suzukii will be granted.”

Pathogens Early detection is essential for the management of plant disease, especially for bacterial diseases such as bacterial spot of Prunus (caused by Xanthomonas arboricola pv. pruni; Xap), bacterial canker of kiwifruit (due to Psa) and angular leaf spot of strawberry (caused by Xanthomonas fragariae). Diagnostic assays, based on loop-mediated amplification (LAMP) have been developed for all three bacterial pathogens. Diagnosis can be achieved in 30 minutes in the field, and could be developed into commercial kits for on-site pathogen detection.

There are no effective strategies for the control of these bacterial diseases

in the EU. Dropsa has been developing novel products, formulations and delivery technologies. A novel antimicrobial peptide was effective at controlling kiwifruit, peach and strawberry pathogen infections. The peptide is biodegradable and with very low toxicity. Stem injection methods have been developed to deliver antimicrobial peptides,

which protected kiwifruit and peach plants against infections of Psa and Xap. Biological control agents (BCAs) were identified and evaluated, resulting in two potential candidates (Lactobacillus plantarum and Bacillus amyloliquefaciens) that are being developed as novel microbial pesticides. The bacteria were produced by

Drosophila suzukii monitoring trap on a netted cherry tree © N. Audsley (Fera).

Experimental plot testing netting on individual Cherry trees to exclude Drosophila suzukii. © N. Audsley (Fera).

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DROPSA Strategies to develop effective, innovative and practical approaches to protect major European fruit crops from pests and pathogens

Project Objectives

To develop reliable, robust and cost-effective approaches to protect the major European fruit crops from Drosophila suzukii, and bacterial pathogens. This has been achieved by investigating their pathways of introduction, determining their biology, ecology and/ or epidemiology to develop innovative, preventative and integrated control solutions, and developing forecasting and decision support systems and risk mapping as a component of integrated pest management.

Project Funding

FP7-KBBE-Control of pests and pathogens affecting fruit crops

Project Partners

Fera (UK) • Stichting Dienst Landbouwkundig Onderzoek (Netherlands) • Cab International (Switzerland) • Universitat De Girona (Spain) • Alma Mater Studiorum-Universita Di Bologna (Italy) • University of Leeds (UK) • Imperial College London (UK) • Consiglio per la Ricerca E La Sperimentazione In Agricoltura (Italy) • European and Mediterranean Plant Protection Organisation (France) • Institut National De La Recherche Agronomique (INRA) • Endoterapia Vegetal (Spain) • Oxitec Ltd (UK) • Julius Kühn-Institut (Germany) • Zurcher Hochschule Fur Angewandte Wissenschaften (Switzerland) • Agriculture and Agri-Food Canada • The New Zealand Institute for Plant and Food Research Limited • United States Department of Agriculture • Yunnan Agricultural University (China) • Pherobank BV (Netherlands) • Agrifutur SRL (Italy) • Hokkaido University (Japan) • Ecologia Proteccion Agricola SL (Spain) • Handelsonderneming Vlamings BV (Netherlands) • Instytut Ogrodnictwa (Poland)

Contact Details

Dr Neil Audsley, Project Coordinator Fera Science Limited Sand Hutton York, North Yorkshire YO41 1LZ United Kingdom T: +44 1904 462628 E: dropsa@fera.gsi.gov.uk W: www.dropsaproject.eu

Male (left) and female Drosophila suzukii on a strawberry © Fera .

fermentation processes in a bioreactor, and innovative formulations have also been developed to improve the fitness of the BCAs. Preliminary field tests have confirmed the efficacy of both bacteria for control of the quarantine bacterial diseases.

More extensive field testing is in progress in different areas of Spain and Italy.

Management methods Although methods have been developed to help manage these pests and pathogens, no one single strategy is going to be effective, so the emphasis in the project was on integrated pest management. “Working with fruit growers, both chemical and nonchemical methods have been evaluated in the field,” says Dr Audsley. “This includes the use of nets to protect the fruit from flies,

Brown spot on Kiwi vines infected with Pseudomonas syringae. © F. Spinelli (UNIBO).

and orchard management, such as mowing, pruning diseased plants, and removing and destroying fruit after harvest.”

The wider goal of this research was to develop improved management methods to help reduce fruit losses from insect pests and pathogens. Around 14 percent of all potential food production globally is thought to be destroyed by insect pests, while it has been estimated that the EU fruit industry loses 3 million tonnes of produce due to pests and pathogens, underlining the wider importance of the project’s work and sharing best practice. “We interact closely with the industry and with growers,” says Dr Audsley. “Workshops and clinics have been held over the course of the project for example, helping to inform growers about the best way to protect their crops.“

We’ve been looking at parasitic wasps that attack Drosophila suzukii. This is both parasitoid wasps that are native to Europe and also parasitoids from Asia, where Drosophila suzukii originates

Dr Neil Audsley

Dr Neil Audsley is an invertebrate physiologist with more than 30 years of experience. He provides strategic research and development for the management of native, invasive and emerging pests of agriculture, horticulture and tree health importance. His major research interests include invertebrate physiology and endocrinology, alternative pesticides, insecticide resistance and integrated pest management.

He manages collaborative projects for UK government and the European Commission.

Parasitic wasp on a blueberry searching for Drosophila suzukii larvae © T. Hayes (CABI) .

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