Effects of multiple biological control agents on <i>Drosophila suzukii</i> (Diptera: Drosophilidae) in the laboratory, greenhouse, and field

Drosophila suzukii Matsumura is a nearly worldwide invasive pest that causes damage to ripening fruit, particularly raspberries. Biological control in an integrated pest management strategy may be an alternative to repeated insecticide applications. We evaluated the effects of using multiple commercially available agents against D. suzukii in raspberries. In the laboratory, the combination of the pupal parasitoid Muscidifurax raptorellus Kogan and Legner (Hymenoptera: Pteromalidae) and predators Orius insidiosus Say (Heteroptera: Anthocoridae) and Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) reduced D. suzukii to the lowest level compared to any 1 species or 2 species combinations in a substitutive design. However, in caged plants with ripening fruit in a greenhouse, M. raptorellus and O. insidiosus together were more effective against D. suzukii than the 3 species combination. In high tunnels, M. raptorellus and O. insidiosus were ineffective against D. suzukii, and spinosad applications with or without M. raptorellus and O. insidiosus resulted in equally low numbers of D. suzukii. In the field, M. raptorellus and O. insidiosus and Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae) releases in raspberry plots with sweet alyssum were less effective against D. suzukii than spinosad applications to plots with or without sweet alyssum as a banker plant. Hymenoptera, particularly Figitidae: Eucoilinae as determined by barcoding, were more abundant in raspberries adjacent to sweet alyssum than in raspberry plots without sweet alyssum. With the discovery and redistribution of figitid parasitoids of larval D. suzukii, future research on their effects in combination with banker plants like sweet alyssum and releases of predators is needed.