Fine-mesh exclusion netting reduces Drosophila suzukii (Diptera: Drosophilidae) infestation and improves organic fall-bearing raspberry yields

The economical production of small fruits has been significantly complicated by the spotted-wing drosophila, Drosophila suzukii Matsumura, throughout its invaded rage. Fall-bearing red raspberries are especially susceptible to D. suzukii, and significant efforts to mitigate their damage are undertaken by growers. Exclusion barriers made from fine-mesh netting has emerged as an organic compliant strategy to mitigate damage from D. suzukii. Identifying less susceptible raspberry cultivars may also alleviate D. suzukii damage. Key pollination complications arise from exclusion-based tactics, but properly timing exclusion establishment may provide a remedy. In a 2-yr-old fall-bearing raspberry planting containing 3 cultivars, exclusion barriers were erected at 2 phenological timings. Spinosad- and pyrethrin-based pesticides were also applied to separate rows throughout harvest and a fourth treatment group matured without management. A subsection of raspberries was harvested and examined for marketability or damage, and D. suzukii adult populations were sampled with baited traps. An exclusion barrier applied early in fruit development was the most effective pest management strategy of those we tested. Its use decreased D. suzukii captures by 75%, decreased D. suzukii-infested fruit weights by 48%, and increased marketable yield by 63% compared to the no management control; however, it also increased pollination deficient fruit weights. Exclusion netting applied later in fruit maturation also decreased D. suzukii captures, infested fruit weights, and the weight of fruits damaged by other arthropod pests but did not significantly increase marketable yield. Our results indicate that netting exclusions may hold promise for the economical production of fall-bearing raspberries.