Local and foreign field surveys of parasitoids of Drosophila suzukii

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a destructive crop pest native to Southeast Asia that recently invaded countries in Europe and North America, severely impacting commercial fruit production in its new host range. Here we report the results of a coordinated field survey aimed at determining the presence and seasonal phenology of indigenous D. suzukii parasitoid populations in Willamette Valley of Oregon and Trento Province, Northern Italy. Sentinel traps with fruit or agar-based host substrates were baited with D. suzukii and placed in a range of commercial soft fruits and natural non-commercial habitats. The generalist pupal parasitoid Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae) and larval parasitoid Leptopilina heterotoma Thomson (Hymenoptera: Figitidae) were collected from D. suzukii pupae and rates of parasitism were estimated. Collected individuals were reared to establish laboratory colonies of each species. Subsequent controlled experiments confirmed the ability of each parasitoid to utilize D. suzukii as a host and compared reproductive success between hosts, host substrates, regional strains, and life stages. The results of these studies will be presented. In response to relatively low rates of parasitism by indigenous parasitoids, foreign exploration was conducted in two consecutive growing seasons in South Korea to survey and collect parasitoids of D. suzukii in its native range using similar methodology as described above. Two larval parasitoids, Asobara sp. (Braconidae) and Ganaspis sp. (Figitidae), and two pupal parasitoids Pachycrepoideus sp. (Pteromalidae) and Trichopria sp. (Diapriidae) were collected from D. suzukii pupae. Collected indivisuals were reared in quarantine to begin testing for host preference and specificity. Results of the field collections in South Korea will be presented.