Host location and dispersal ability of the cosmopolitan parasitoid Trichopria drosophilae released to control the invasive spotted wing Drosophila

Although several parasitoid species attack the pest under laboratory conditions, information is lacking on their host-finding and dispersal capabilities in natural environments. We tested the effect of repeated parasitoid releases on D. suzukii populations in infested orchards. The pupal parasitoid Trichopria drosophilae (Perkins) was released on different crops at eight sites. Parasitism was monitored using traps placed at various distances from the parasitoid release point (RP). A second experiment was carried out under semi-field conditions to evaluate augmentation of the parasitoid. In both experiments, D. suzukii infestation was evaluated through fruit samplings, both from the plant, and from the ground. In the open field trials, T. drosophilae attacked D. suzukii in traps up to 40m away from the RP, and pest emergence was significantly reduced within a radius of 10m at seven out of eight sites. In the semi-field trials, parasitoid releases significantly reduced D. suzukii emergence from ground-sampled fruit, and augmentation enhanced parasitism, increasing the numbers of parasitoids emerging from host pupae. Although further field studies are required, these results suggest that T. drosophilae may be considered a potential biocontrol agent for D. suzukii.