The Sterile Insect Technique can efficiently reduce the reproduction of the spotted wing drosophila (Drosophila suzukii) in strawberry

Abstract

The spotted wing drosophila (SWD) Drosophila suzukii (Diptera: Drosophilidae) is a highly problematic pest in soft fruit crops. Since its introduction in Europe in 2008, no satisfying nor environment-friendly control method has emerged against this species. The sterile insect technique (SIT) has proven efficient at controlling numerous fruit fly species. In recent years, key elements of SIT against D. suzukii have become available, leading to the publication of encouraging results. However, field- and field- like experiments are notoriously under the influence of various, often unidentified factors granting the need for replicated studies. In this experiment, we assayed the efficacy of a high-performance strain at reducing the reproduction of D. suzukii in complex, yet replicated and controlled conditions. Two ratios of sterile to fertile insects (5:1 and 1:1) using bisexual releases were compared to a control treatment with fertile, wild flies only. The presence of sterile individuals at a 5:1 ratio significantly reduced fly reproduction, measured after 5 days, by an approximate threefold factor. However, the proportion of infested fruits in the treated plots remained unaffected. The number of available berries in the cage appeared as an unexpected determinant of fly infestation, suggesting undocumented density-dependent processes. The success of this assay opens the door to larger scales experiments, over several generations, and, in the near future, the field-evaluation of the efficacy of the SIT to control D. suzukii.