A survey on parasitoids of the spotted wing fly, Drosophila suzukii, in vineyards and other agroecosystems of Trento province

Drosophila suzukii (Matsumura) (Diptera Drosophilidae), is an invasive species native of Eastern and Southeastern Asia. Since its introduction in USA and Europe in 2008, this pest caused hundred thousand dollars worth of damage to small and stone fruits business. Also grapevine, has been shown to be attacked by the pest in late season. Observations in vineyards in Northern Italy indicate that V. vinifera can become a field host, and soft skinned varieties are the more impacted. The severe damages done by D. suzukii are mainly due to the absence of specialized natural enemies, able to control the population outbreaks of the introduced species in the invaded regions. Here we report the results of a survey aimed at determining the presence of indigenous D. suzukii parasitoid populations carried out in 2012 and 2013, from May to October, in four locations of Trento Province (Italy). 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 fruit 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. In late season 2012, 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. During the first part of season 2013 another species, the larval parasitoid Leptopilina heterotoma Thomson (Hymenoptera: Figitidae), hatched from both drosophila’s species baited traps. Successive parasitism efficacy tests were set up under controlled conditions confirming the ability of both the species to attack D. suzukii. The possible practical implications of this finding for the biological control of D. suzukii are discussed.