Assessing native parasitoids of the invasive pest Drosophila suzukii in the southeastern US

Authors: NEUPANE, SUBIN - Agriculture University Of Georgia; SCHMIDT, JASON - University Of Georgia; SYNDER, WILLIAM - University Of Georgia; WANG, XIN-GENG - University Of California Berkeley; Buffington, Matthew; DAANE, KENT - University Of California Berkeley; SIAL, ASHFAQ - University Of Georgia

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2024
Publication Date: 10/24/2024
Citation: Neupane, S., Schmidt, J., Synder, W., Wang, X., Buffington, M.L., Daane, K., Sial, A. 2024. Assessing native parasitoids of the invasive pest Drosophila suzukii in the southeastern US. Environmental Entomology. 53(6):966-972. https://doi.org/10.1093/ee/nvae086.
DOI: https://doi.org/10.1093/ee/nvae086

Interpretive Summary: The spotted wing drosophila (SWD) is a major fly pest of fruit worldwide. While pursuing control measures for this fly, natural enemy wasps that kill these flies have been discovered in Asia, and brought to the United States for release. In order to gauge the establishment of these wasps, the native wasp fauna must be evaluated first, documenting the status of this fauna prior to release. In this case, the native wasp fauna was evaluated in GA, serving as a good estimate for the SE United States. Biological control researchers, pest managers, and ecologists will be able to use these baseline data to evaluate the effectiveness and establishment of newly release biological control agents.

Technical Abstract: Drosophila suzukii (Matsumura) (Diptera Drosophilidae), commonly known as Spotted-Wing Drosophila (SWD), is an invasive insect pest threatening many small fruit farms in the Americas and Europe for more than a decade. Biological control using parasitoids is a promising strategy for improving the sustainable management of SWD. For the execution of effective biological control initiatives targeting SWD through augmentation and classical release of parasitoids, it is necessary to recognize and understand the presence and preference of native parasitoids at their local adaptation. We conducted two season-long field explorations of native parasitoids of SWD during 2021 and 2022 at major blueberry-producing locations in southeast Georgia, United States. Fruit-baited sentinel traps infested with SWD eggs were placed around eight commercial blueberry orchards. A total of 371 parasitoids of Drosophila were collected and classified into three families: Figitidae, Pteromalidae, and Diapriidae. Among them, Leptopilina boulardi (Hymenoptera: Figitidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) were the most abundant species in these collections. The number of parasitoids captured was higher during peak blueberry ripening through the end of harvest season, compared to during flowering, fruiting, or post-harvest. Parasitoids were most abundant in unmanaged locations compared to blueberry fields, although we found no difference between blueberry fields managed using organic versus conventional practices. Previously, out of native parasitoids, only P. vindemiae was known to successfully parasitize SWD. To confirm parasitism by L. boulardi and estimate rates, we conducted a laboratory test and found that L. boulardi parasitized SWD larvae at a low rate of 7% and none of the larvae emerged from the parasitized SWD host. This is the first survey of any Drosophila-related native parasitoid in the eastern US, and our findings serve as the baseline for future studies to document the release of native or exotic parasitoids in blueberry-producing counties elsewhere. Ultimately, we found that the existing parasitoids were inadequate to suppress the SWD in these locations. Planned intervention with the classical release of specialist parasitoids along with the existing SWD management approaches was deemed necessary in these areas.