Border Sprays and Cultivation Tactics for Control of Drosophila suzukii (Matsumura) in Organic Blackberries

Drosophila suzukii (Matsumura), an invasive fruit fly pest (Diptera: Drosophilidae) from Southeast Asia, attacks healthy thin-skinned fruits. Estimated losses are >60 mil USD in the eastern U.S., partly due to increased insecticide use. Organic growers have been particularly affected due to limited tools, and therefore, require new tactics for D. suzukii management. In a two-year study conducted in organic blackberries, border sprays and between-row cultivation were evaluated for their potential to suppress D. suzukii populations. The experiment was a completely randomized two-factor split plot design with eight replicated. Entrust® (spinosad) was applied on both experimental plantings prior to treatment applications. One planting received two border sprays of Azera® (azadirachtin + pyrethrins) at 7-d intervals. Aisles were tilled to 15.24 cm in half of each planting. Adult flies were monitored weekly using clear, 1-L plastic traps baited with a yeast sugar mixture and hung in the bush center. Larvae were monitored by collecting berry samples weekly. Non-target insects and natural enemies were also assessed. Results from both years showed that border sprays suppressed D. suzukii populations. Additionally, tillage further reduced D. suzukii populations, suggesting the potential of cultivation tactics for D. suzukii management.