Augmentative releases of Trichopria drosophilae for the suppression of early season Drosophila suzukii populations

Biological control agents may play an important role in regulating Drosophila suzukii Matsumura (Diptera: Drosophilidae), particularly after the winter population bottleneck. Here we test the ability of the cosmopolitan pupal parasitoid, Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae), to reduce early season D. suzukii populations. We performed augmentative releases of the parasitoid during late March-April and carried out extensive monitoring activity on both parasitoid and fly populations. Results clearly showed a mitigation of the D. suzukii population in the treated areas, associated with a higher T. drosophilae parasitism. A 34% reduction in fruit infestation was observed in the unmanaged vegetation surrounding orchards. Accordingly, pest eclosion was significantly lower in the treated area compared to the untreated one. Our results suggest that augmentative release of T. drosophilae can improve pest control of D. suzukii in the unmanaged areas surrounding the crops, thus lowering the severity of pest outbreaks in the orchards.