Did they make it? A two-year study on the field establishment and effectiveness of Ganaspis brasiliensis in Delaware

Spotted wing drosophila (SWD) is an invasive species of fruit fly that plagues commercial, soft skinned fruit crops, such as blueberries, strawberries and cherries, throughout North America. Pesticides have proven ineffective and costly, as SWD utilizes surrounding native flora as a refugia and reinfest crops after routine sprays. Thus, a need for a biological control agent arose. Several larval parasitic wasps were selected as potential candidates, with the best proving to be Ganaspis brasiliensis. Two strains, dubbed G1 and G3, were chosen as primary agents. G1 proved to be the best candidate and was permitted for release in 2021. Releases of G1 began along both the east and west coasts of the United States in the summer of 2022, with the majority of releases occurring in Newark, DE. Sites were selected based on availability of native host plants throughout the field season. Three locations were chosen, including two state parks and the Beneficial Insects Introductory Research Unit (BIIRU). Two release sites per location were utilized over three release periods. Approximately 10,000 wasps were released throughout the season and pre and post fruit sampling methods were employed to monitor the establishment of G1 and presence of SWD. These sample methods, coupled with apple cider vinegar and sentinel traps, are planned for the summer of 2023, and hope to provide insight to the establishment of G1 in a field setting.