AGRE-0062 Control of Whitefly in Greenhouses Under Shelter and Outdoors with the Aid of Entomephagi Specific Parasites and Polyphagous Predators

SUMMARY

Protected crops are subject to attack by various insects and mites. Major pests include whiteflies (Trialeurodes vaporariorum and Bemisia tabaci) and the red spider mite (Tetranychus urticae) which have in the past been controlled with varying success using chemical pesticides. However, in many areas these pests have become resistant to the majority of pesticides used. The objective of this project was to develop efficient, alternative, biological solutions to this problem specifically adapted to the climatic conditions found in the Mediterranean region under glass or plastic cover. A number of natural enemies of the pests were identified and production and control methods optimised.

INTRODUCTION

Protected crops, that is horticultural produce such as tomatoes, peppers and cucumbers, as well as flowers and ornamental plants grown in glasshouses or plastic tunnels, are subject to attack by various insects and mites. Major pests include whiteflies (Trialeurodes vaporariorum and Bemisia tabaci) and the red spider mite (Tetranychus urticae) which have in the past been controlled with varying success using chemical pesticides. However, in many areas these pests become resistant to the majority of pesticides used. The objective of this project was to develop efficient, alternative, biological solutions to this problem specifically adapted to the climatic conditions found in the Mediterranean region under glass or plastic cover.

ACTIVITIES

In the first stage, natural enemies of the pests under consideration were collected and identified. As a result 7 species have been tested. These were 5 parasitoid parasites of whiteflies, 1 predator species of whitefly and 1 mite predator species. The whitefly parasitoids belong to the genera Eretmocerus (Er. mundus) and Encarsia (En. formosa, En. pergandiella, En. tricolor and En. hispida) from the Aphelinid family; the last 2 Encarsia spp. Are new to the French fauna. The entomological fauna associated with Bemisia tabaci is relatively poor in Sicily where only En. Pergandiella and Er. mundus have been found. The whitefly predator is the predatory bug Macrolophus caliginosus (Heteroptera: Miridae) and the mite predator is Phytoseiulus persimilis (Phytoseidae) of which 3 strains were collected: "SI" wild Sicilian strain, "CE" wild north Italy strain and "BU" a commercial strain which has been reared artificially for a long time. A standard method was refined in order to determine the potential benefits of whitefly parasitoids (Encarsia spp.), the whitefly predators and the 3 strains of P. persimilis. The best expression of biotic potential (fecundity, longevity and predation) of the whitefly parasitoids was obtained from egg-laying boxes which showed a mean fecundity of 205 eggs/female for En. formosa and 150 eggs for En. hispida at 22°C. The mean fecundity of Er. Mundus was significantly less. Other factors, such as time spent in searching for the host, the length of each embryonic and larval stage, as well as mortality, were studied as a function of temperature and of the plant host. Studies extended to electron microscopic examination (providing anatomical description of the ovipositor and egg). A study of the embryogenesis of the eggs of M. caliginosus from mature females was carried out. For Phytoseiulus persimilis, the strain "SI" was found to be superior to the other strains in terms of fecundity (48 eggs compared to 24).

It was found possible to produce B. tabaci parasitoids, Encarsia and Eretmocerus on tobacco (Nicotiana tabacum or N. glauca) and hibiscus plants. Artificial medium were developed for the oviposition of M. caliginosu resulting in larvae which were perfectly viable. Later transfer on to tobacco gave the best yield of adult M. Caliginosus. The optimal number of females per cage was determined and a method of picking up the females by aspirator was developed. New quality control standards and alternatives to the specifications of the IOBC were established. They will be proposed for Encrasia formosa, Phytoseiulus persimilis and Macrolophus caliginosus.

Recommendations have been made concerning the methods of release of parasitoids and predators under controlled conditions, including controlled climatic conditions when they are used in professional greenhouses. Methods of mass production were explored. In the case of En. formosa, a pilot production was set up resulting in a good production of a quality adapted to Mediterranean conditions. For the predatory bug, M. caliginosus, methods of production adapted to the Mediterranean climate were also defined, assuring the production of a quality organism. In the case of P. persimilis, an efficient technology transfer associated with good knowledge of the Mediterranean habitat resulted in optimisation of the mass production of this predator. In order to optimise conditions of use of natural enemies in integrated control, various proposed control systems were tested under professional conditions for a number of crops. For tomatoes, courgettes and Gerbera, as soon as the action threshold of the whitefly was reached a defined number of E. formosa were released. Tests over 250 ha allowed a verification of the biocontrol of the whitefly in 6 Italian provinces. For validation of the strategy employed for M. caliginosus, tests were carried out on more than 35 ha of crops, leading to an adaptation of the protection strategy (predator used singly or in association with En. formosa) as a function of the initial pest densities and the type of culture (Autumn or Spring). In order to validate the proposed integrated pest management (IPM) strategies, two models of simulated parasitism (host T. vaporariorum - parasitoid En. formosa) and predation (prey T. urticae - predator P. persimilis) were constructed. These were verified, first under lab conditions, then in the greenhouse. Strawberry, eggplant, pepper, courgette, melon and gherkin were selected as study targets in order to define a general background of integrated pest control which included other natural enemies (predators of aphids and thrips) associated with selective pesticides. The improvement in production methods and utilisation led to the production of several million predators.

CONCLUSIONS

This project provided additional knowledge of protected crops, functioning of host-parasitoid, predator-prey associations and methods for the integrated crop protection of greenhouse crops under Mediterranean conditions. This has enabled a functional decision making model to be constructed together with an associated database. Advice on action can be obtained, based on information on the initial conditions of the crop, physical and agronomic specifications of the greenhouse and the presence and abundance of pests. This can be either based on an integrated approach using En. Formosa, P. persimilis or a combination of actions associating natural enemies, fungicides and selective insecticides. A technical pamphlet was produced which gave comprehensive information to the professional greenhouse growers.

PARTICIPANTS

Institut National des Sciences Appliquées de Lyon (France), Istituto di Entomologia de Bologne (Italy), ENEA de Rome (Italy), SCAM de Modène (Italy), Centrale Ortofrutticola de Cesena (Italy), Duclos-Agrobiotech (Ciba-Bunting France) Septèmes (France), Ciba Bunting Control Ltd Colchester (UK)