Discrimination abilities and parasitism success of pupal parasitoids towards spotted-wing drosophila pupae previously parasitized by the larval parasitoid Ganaspis brasiliensis (Hymenoptera: Figitidae)

Authors: Hougardy, Evelyne; Hogg, Brian; Wang, Xingeng; DAANE, KENT - University Of California Berkeley

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2022
Publication Date: 10/31/2022
Citation: Hougardy, E.H., Hogg, B.N., Wang, X., Daane, K.M. 2022. Discrimination abilities and parasitism success of pupal parasitoids towards spotted-wing drosophila pupae previously parasitized by the larval parasitoid Ganaspis brasiliensis (Hymenoptera: Figitidae). Environmental Entomology. 51(6):1106-1112. https://doi.org/10.1093/ee/nvac083.
DOI: https://doi.org/10.1093/ee/nvac083

Interpretive Summary: The spotted wing drosophila is an invasive fruit fly pest of small and soft fruit crops worldwide that appears to lack effective natural enemies in the USA. A parasitic wasp from Asia that may help control this pest has recently been approved for release in the USA. This parasitic wasp lays its egg in the small fly larva, and the wasp larva then develops and emerges from the fly pupa. This study investigates possible competition between this introduced parasitic wasp and two other parasitic wasp species that are already present in North America and are also capable of attacking the spotted wing drosophila, although less efficiently. These two parasitic wasps lay their eggs in the fly pupae. We found preliminary evidence that the two pupal parasitic wasp species avoid laying their eggs in previously parasitized pupae. One pupal parasitic wasp species was able to successfully develop on the fly pupae containing all sizes of the developing larval parasitic wasps. The other pupal parasitic wasp species was only able to successfully develop on fly pupae containing small larvae of the introduced wasps. These results suggest that the two pupal parasitoids can attack pupae parasitized by the larval parasitoid and may impact the larval parasitoid after it is released.

Technical Abstract: Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae) are two cosmopolitan and generalist pupal parasitoids that are among a few of the resident parasitoids in North America capable of attacking Drosophila suzukii (Matsumura), an invasive pest of small and soft fruit crops worldwide. Ganaspis brasiliensis (Ihering) is a specialist larval parasitoid of D. suzukii that was recently approved for biological control introduction against D. suzukii in the USA. As a solitary koinobiont species, G. brasiliensis oviposits in the host larva but emerges as an adult from the host puparium. This study investigated the discrimination ability and parasitism success by these pupal parasitoids towards D. suzukii pupae previously parasitized by G. brasiliensis, to examine whether interactions with resident parasitoids will affect G. brasiliensis after it is released in the USA. We found prelimenary evidence that neither pupal parasitoid could discriminate towards D. suzukii pupae parasitized by early instars of G. brasiliensis. Pachycrepoideus vindemiae was able to successfully develop on D. suzukii pupae containing all preimaginal stages of G. brasiliensis, although parasitism success was significantly higher on those bearing later rather than early stages of G. brasiliensis. Trichopria drosophilae was only able to successfully develop on D. suzukii puparia containing early instars of G. brasiliensis. These results suggest that D. suzukii parasitized by the larval parasitoid could be subsequently attacked by the pupal parasitoids.