Landscape Influences and Preventive Management For Drosophila Suzukii In Small Fruit Crops

Small fruit production has been greatly challenged by the repeated invasion of non-native arthropod pests, impacting economic feasibility, and increasing the need for insecticides. Spotted wing drosophila (Drosophila suzukii (Matsumura)) is the most recent invasive pest of small fruits. It causes damage by ovipositing beneath the skin of ripening fruits. Its wide-spread distribution and development of resistance to insecticides has resulted in the need for improved alternative management strategies for small fruit growers. My surveys of D. suzukii at thirteen blackberry (Rubus fruticosus L.) and raspberry (Rubus idaeus L.) fields found that while D. suzukii was present within every fruit sampling locality, traps placed in fruit plantings had higher relative abundance than non-host crop fields and turfgrass fields. Turfgrass fields had lower relative abundance than semi-natural areas and non-host crop fields. Additionally, D. suzukii abundance was correlated with the length of semi-natural habitat edge surrounding farms suggesting a link between this landscape feature and the distribution of D. suzukii in fruit fields. The physical exclusion of insects is beginning to see use as an alternative pest management strategy for small fruits. By physically excluding D. suzukii through the deployment of fine-mesh nets over blackberry rows, I found that fine-mesh exclusions increased marketable yields and reduced D. suzukii captures and larval presence within fruits compared to rows treated with the most efficacious organic insecticide, spinosad. Fall-bearing raspberry production presents challenges to the use of exclusion barriers, as some raspberry cultivars flower asynchronously and repeatedly each season. By establishing fine-mesh exclusions at two phenological timings, I found exclusions applied early in fruit development increased marketable yields and reduced D. suzukii captures and infested fruit weights compared to rows untreated for D. suzukii. Exclusions applied late in fruit development also provided pest control benefits but did not increase marketable yields compared to control rows nor rows treated with organic insecticides. Finally, previous research has also studied the efficacy of fine-mesh exclusions. My review of physical barrier uses in agriculture uncovered twelve publications across cherry (Prunus avium L.), blackberry (Rubus fruticosus L.), blueberry (Vaccinium corymbosum L. and Vaccinium angustifolium Aiton), wine grape (Vitis vinifera L.), and raspberry crops (Rubus idaeus L.). Eleven out of twelve papers found that these barriers are effective at reducing D. suzukii presence and infestation of fruits, while three out of seven papers found that netting can increase the yields of marketable fruits. Throughout this work, I found fine-mesh exclusions can reduce D. suzukii infestation and improve marketable yields in blackberries and raspberries without insecticide usage. In a time where pest management practices are adapting to threats from climate change and invasive species, my work built a body of literature on alternative practices and expanded available IPM strategies