Laboratory evaluation of effects of powdered sulphur on the oviposition, fruit detection and behaviour of Drosophila suzukii (Diptera: Drosophilidae) on strawberry.
Drosophila suzukii (Matsumura, 1931) is an invasive pest from South-East Asia that can damage a wide range of soft-skinned fruit crops (especially berries) resulting in serious financial losses. At present, control of D. suzukii is still mainly based on adult-oriented chemical pesticides that is likely to result in resistance and environmental pollution. In this context, alternative methods that are compatible with sustainable management are required. Sulphur and its different formulations are widely used for a long time as a fungicide and insecticide on many crops as it is environmentally-friendly and compatible with organic management. In this study, the effect that powdered sulphur-treated strawberries had on oviposition were evaluated under laboratory conditions in order to confirm the findings of a previous report on blueberries. No-choice and choice experiments were carried out to assess whether powdered sulphur affected the ability of the fl y to detect fruit, altered its behaviour or did both. The treatment of strawberries resulted in a reduction of over 79% in the total number of D. suzukii that developed. In the no-choice experiment, there was a reduction of over 70% in the time the flies spent on treated compared to untreated fruit. In the choice experiment, 57% of the females chose untreated and 43% treated strawberries, but this difference was not statistically significant. Furthermore, females took over 75% longer to visit the treated fruit than the control. Sulphur had no noteworthy effect on fly behavior, although oviposition only occurred on untreated fruit indicating that sulphur affects the acceptance and suitability of fruit for females. These results indicate that powdered sulphur could be an appropriate alternative to synthetic-organic insecticides for controlling D. suzukii and is compatible with organic crop management and waste reduction strategies.