Laboratory and field trials to identify effective chemical control strategies for integrated management of Drosophila suzukii in European cherry orchards

The recent spread of the Spotted Wing Drosophila (SWD), Drosophila suzukii, in Europe has created considerable concern because of the damage recorded on various crops, in particular on sweet cherry, despite the use of conventional pesticides. Effective chemical control strategies are urgently required to improve integrated SWD management. Insecticide use should be incorporated in an IPM strategy that adopts cultural and biological control methods and tools to ensure high protection of cherry production while fulfilling export market requirements. Laboratory and field trials were conducted in North-Eastern Italy to identify the most effective and sustainable insecticides to be used against SWD in cherry orchards. In the laboratory, cherries previously infested by SWD were dipped in insecticide solutions to assess their effectiveness in controlling eggs and larvae. In other laboratory trials cherries were first treated with insecticides and then exposed to adults to assess residual activity. A number of chemical control strategies (including one designed for organic orchards) were then compared in cherry orchards. These strategies were planned also considering the need to control the European cherry fruit fly Rhagoletis cerasi L., a key pest of cherry in Europe and elsewhere. A number of formulations based on cyantraniliprole, spinosad, spinetoram, phosmet, lambda-cyhalothrin and deltamethrin were effective against different life stages of SWD in the laboratory. SWD control in the field was influenced by the use of above-mentioned insecticides and the number of applications during the cherry ripening period. Insecticides selected for the protection of organic cherry orchards were almost ineffective. Some strategies defined for conventional orchards were also effective against R. cerasi. In most cases (dimethoate was the exception) insecticide residues were lower than maximum residue limits required by the European Union to export cherries to major markets. In conditions of high pest pressure, three to four applications with active ingredients having different modes of action were needed to keep D. suzukii and R. cerasi damage beneath economic thresholds. Sanitation and harvest management could be helpful in lowering pesticide use. A number of tactics such as insect-proof nets, biological and cultural methods should be incorporated for an effective IPM strategy with benefits not only for human and environmental health but also in terms of the lifetime of currently effective insecticides.