Application strategies for reducing insecticides in Drosophila suzukii management

Since the arrival of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), field applications of broad-spectrum insecticides have significantly increased to protect susceptible fruit from infestation in berry crop production. Field studies were conducted from 2011 to 2013 to determine whether alternate row middle or border treated reduced spray programs could manage D. suzukii as well as complete sprays and have less of an impact on non-target arthropods. Four raspberry sites and one blueberry site were alternate row middle and border sprayed, respectively. Captures of D. suzukii were compared to conventional complete spray programs. Non-target arthropods were evaluated 7 d post-harvest. In both reduced spray trials, no differences in mean adult numbers and larvae of D. suzukii were detected between treatments. Mean counts immediately after sprays (i.e., 3 – 12 d after treatment) were also similar in complete and alternate row sprays. Both reduced spray strategies had significantly more Stethorus spp.; additionally, alternate row sprays had significantly more Psyllobora spp. No difference in fruit knockdown by complete or border spray was observed. These reduced pesticide strategies are additional tools to consider in D. suzukii IPM programs that reduce amount of spray area, application time, and input costs while conserving natural enemies.