First field records of Pachycrepoideus vindemiae as a parasitoid of Drosophila suzukii in European and Oregon small fruit production areas

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 survey aimed at determining the presence of indigenous D. suzukii parasitoid populations carried out from May to October 2012 in two areas negatively affected by this fruit pest: Trento Province, Northern Italy, and Oregon in the Pacific Northwest of the USA. We conducted field and laboratory studies in order to determine the status of biological control agents utilizing D. suzukii as a host. Our study sites included a range of commercial soft fruits and natural non-commercial habitats. In each site, sentinel traps were baited with either D. suzukii or Drosophila melanogaster Meigen (Diptera: Drosophilidae) larvae in different food substrates. The generalist parasitoid, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae), was collected from both D. suzukii and D. melanogaster pupae in traps deployed in a selection of these sites. This report of P. vindemiae in 2012 represents the first identification of D. suzukii parasitoids in Europe. A successive parasitism efficacy test was set up under controlled laboratory conditions confirming the ability of P. vindemiae to attack D. suzukii pupae. In addition, an historical digression with analysis of the original documents in the Italian archives has been provided in order to unravel the correct species name. We finally discuss the possible practical implications of this finding for the biological control of D. suzukii.