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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #419177
Research Project: Biological Control of Invasive Pests in Agroecosystems and Wetland, Forest and Rangeland Ecosystems in the Far Western U.S.

Location: Invasive Species and Pollinator Health

Title: A novel method to produce safe sentinel eggs for the field monitoring of stink bug parasitism using unmated females

Author
item Hougardy, Evelyne
item Hogg, Brian

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2025
Publication Date: 7/7/2025
Citation: Hougardy, E.H., Hogg, B.N. 2025. A novel method to produce safe sentinel eggs for the field monitoring of stink bug parasitism using unmated females. Biocontrol Science and Technology. 35(8):954-963. https://doi.org/10.1080/09583157.2025.2527250.
DOI: https://doi.org/10.1080/09583157.2025.2527250

Interpretive Summary: Bagrada bug is an invasive stinkbug pest of cole crops (cabbage, broccoli, cauliflower, kale, etc.) in the United States. Pesticides are often ineffective against bagrada bugs because they persist in natural habitats surrounding crop fields where pesticides are not applied. Two parasitic wasps were found attacking bagrada bug eggs in California recently. Field monitoring of these parasitic wasps is usually done using stink bug eggs reared in the laboratory. However, these eggs can only be placed in the field for a few days and must be retrieved before the eggs hatch to avoid releasing the stink bug pest in the monitored area. In this study, we used eggs produced by unfertilized (unmated) bagrada bug females. Unmated females are still laying eggs, but these eggs don’t hatch and are sterile. Both parasitic wasps were able to successfully parasitize these sterile eggs. Our results showed that using unfertilized eggs is a suitable alternative to produce safe and reliable eggs to monitor egg parasitism of the bagrada bug and possibly other stinkbug pests.

Technical Abstract: Sentinel eggs used to monitor field parasitism of stink bug pests can only be deployed for a few days to avoid releasing the pest in the monitored area. Using sterile eggs removes the risk of accidental pest introduction and extends deployment time. In this study, sterile eggs produced by unfertilized stinkbug females were tested as an alternative to frozen or irradiated eggs. Using unfertilized Bagrada hilaris, an invasive stinkbug pest of cole crops (cabbage, broccoli, cauliflower, kale, etc.) in the United States, we showed that these eggs successfully sustained the development of Gryon aetherium (Hymenoptera: Scelionidae), the most promising biological control candidate, and Ooencyrtus californicus (Hymenoptera: Encyrtidae), another egg parasitoid attacking B. hilaris in California. Parasitism levels on fresh and 7-day-old unfertilized eggs were comparable to fresh fertilized eggs. In addition, G. aetherium showed no obvious preference for fresh fertilized over seven-day-old unfertilized. This study is the first one to demonstrate the feasibility of using unfertilized eggs produced by unmated females as sentinel eggs to monitor field parasitism of B. hilaris and possibly other species. These eggs come with no risk of accidental release of the pest in the monitored area and remain suitable for parasitism for a longer time window compared to fertilized eggs.