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SWD struggles? Sign up to host parasitoid releases

Marissa Schuh, Integrated Pest Management extension educator 

Spotted wing drosophila (SWD) has been wreaking havoc on US berry production for over a decade now. This invasive fruit fly, which lays its eggs in ripe raspberries, strawberries, cherries, and blueberries, causes millions of damage every year.

Growers in Minnesota have worked to manage this pest with pesticides (both organic and conventional), changing farm infrastructure, picking more often, and cooling fruit.  Even with these measures in place, SWD still regularly damages high value fruit crops. 

Ganapsis brasiliensis is only a few millimeters in size. Photo by Matthew L. Buffington, Ph.D., U.S. Department of Agriculture, Agricultural Research Service, Systematic Entomology Laboratory. 

Ganapsis brasiliensis: Tiny wasp, big potential 

Ganapsis brasiliensis (GB) is a parasitoid wasp native to Asia that showed up in the Pacific northwest on its own.  These wasps are small and solitary, and the driving force in their life is seeking out SWD.  This is because they use SWD to reproduce, laying their eggs inside of the SWD larvae. The developing  wasps feed on the SWD larva, killing it upon emerging as adults.. A single female GB wasp can lay around 100 eggs, and in their native range, parasitism rates of GB can be up to 75% (Girod et al. 2018)

This wasp has been studied and has been determined to pose minimal risks to other insects, and in 2023, universities across the country will be releasing this wasp and studying its ability to parasitize SWD and adapt to new habitats.

Mary Rogers’s organic horticulture lab will be studying this wasp in Minnesota, including releases on farms.  Dr. Rogers is seeking farms that grow berries and use few pesticides to study how well this wasp performs in Minnesota. Fill out the below form to be considered for studies on GB in 2023 and 2024.

For questions, reach out to UMN researcher Eric Burkness (



Bolda, M. P., R. E. Goodhue, and F. G. Zalom. 2010. Spotted wing drosophila: potential economic impact of a newly established pest. Giannini Foundation of Agricultural Economics, University of California.

USDA APHIS. Field Release of Ganaspis brasiliensis (Hymenoptera: Figitidae) for Biological Control of Spotted-wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae), in the

Contiguous United States. 2021.

Girod, P., N. Borowiec, M. Buffington, G. H. Chen, Y. Fang, M. T. Kimura, F. J. Peris-Felipo, N. Ris, H. Wu, C. Xiao, J. P. Zhang, A. Aebi, T. Haye, and M. Kenis. 2018c. The parasitoid complex of D. suzukii and other fruit feeding Drosophila species in Asia. Nature Sci. Rep. 8: e11839

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