Host searching and host preference of resident pupal parasitoids of Drosophila suzukii in the invaded regions

Background: In its invaded regions, Drosophila suzukii (Matsumura) is a novel host for the community of resident parasitoids of Drosophila. To attain a high parasitization rate on the novel host, the parasitoids have to locate it and accept it in the presence of other Drosophila hosts. We conducted a laboratory choice experiment and a semifield trial to investigate host searching and host preference of the three pupal parasitoid species Trichopria drosophilae (Perkins), Pachycrepoideus vindemmiae (Rondani) and Spalangia erythromera Förster.

Results: All three parasitoid species preferred D. suzukii over two common native hosts in the choice experiment. In field cages, most parasitoid offspring emerged from D. suzukii hosts. While P. vindemmiae mainly parasitized hosts in the foliage, most T. drosophilae offspring emerged from pupae presented on the ground.

Conclusions: Both P. vindemmiae and T. drosophilae have the potential to find and parasitize D. suzukii in the field. If released early in the season, possible nontarget effects on native Drosophila should be minimal.