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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 #378881
Research Project: Watershed-scale Assessment of Pest Dynamics and Implications for Area-wide Management of Invasive Insects and Weeds

Location: Invasive Species and Pollinator Health

Title: Natural biological control of Bagrada hilaris by egg predators and parasitoids in north-central California

Author
item Hogg, Brian
item GRETTENBERGER, IAN - University Of California, Davis
item BORKENT, CHRISTOPHER - California Department Of Food And Agriculture
item STOKES, KEITH - Northern Marianas College
item ZALOM, FRANK - University Of California, Davis
item PICKETT, CHARLES - California Department Of Food And Agriculture

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2022
Publication Date: 5/10/2022
Citation: Hogg, B.N., Grettenberger, I.M., Borkent, C.J., Stokes, K., Zalom, F.G., Pickett, C.H. 2022. Natural biological control of Bagrada hilaris by egg predators and parasitoids in north-central California. Biological Control. 171. Article 104942. https://doi.org/10.1016/j.biocontrol.2022.104942.
DOI: https://doi.org/10.1016/j.biocontrol.2022.104942

Interpretive Summary: Bagrada bug is an invasive stinkbug pest of cole crops (broccoli, cauliflower, cabbage, kale, etc.) in California. Insecticides can help control bagrada bug, but are harmful to the environment and cannot be used by organic farmers. An alternative option is biological control, whereby natural enemies (predators and/or parasitic wasps) are used to help suppress pests below damaging levels. As part of an effort to develop a biological control program for bagrada bug, we assessed whether naturally occurring parasitic wasps and predators in California are capable of attacking bagrada bug eggs. A natural enemy that attacks bagrada bug eggs would help prevent this pest from damaging crops. We placed killed (previously frozen) bagrada bug eggs throughout northcentral California, including the Salinas Valley, which is the largest cole crop growing region in the US. A total of 51 sites were sampled over three years. Sentinel eggs were placed on the ground, where bagrada bug lays most of its eggs, and in the foliage of plants, where all other stinkbugs in California lay their eggs and where parasitic wasps are most likely to search. Predation levels were generally higher on the ground than in the foliage, although they varied over time and differed between regions. Burying eggs in sand did not strongly affect predation levels, showing that bagrada bug’s habit of burying its eggs does not provide consistent protection from predators. Of the 35,673 eggs placed in the field over the three years of this study, only 47 (0.13%) were parasitized, and only five of these were on the ground, indicating that few parasitic wasps currently in northcentral California can attack bagrada bug eggs, particularly on the ground. These results show that importing a parasitic wasp from bagrada bug’s native region will likely be necessary to help control bagrada bug in California.

Technical Abstract: Bagrada bug, Bagrada hilaris Burmeister (Pentatomidae), is a damaging stinkbug pest of cole crops (Brassicaceae) in California. Conventional insecticides are currently the most effective means for controlling this pest, but are unavailable to organic growers. As part of an effort to develop a biological control program for bagrada bug, we documented attack rates by resident parasitoids and predators on sentinel bagrada bug eggs throughout northcentral California, including the Salinas Valley, which is the largest cole crop growing region in the US. A total of 51 sites were sampled over three years. Sentinel eggs were placed on the ground, where bagrada bug lays the majority of its eggs, and in foliage, where all other known stinkbug species deposit their eggs and where resident egg parasitoids are most likely to forage. Predation rates exceeded 20% per day on some sample dates, and were generally higher on the ground than in the foliage, although temporal patterns were inconsistent and predation levels varied among the sampled regions. Burying eggs in sand did not consistently reduce predation rates, indicating that bagrada bug’s habit of burying its eggs provides at best only partial protection from predators. Of the 35,673 eggs deployed over the three years of this study, only 47 (0.13%) were parasitized, and only five of these were on the ground, suggesting that few resident parasitoids in northcentral California attack bagrada bug eggs, particularly on the ground. These results show that a parasitoid that co-evolved with bagrada bug in its native range will likely be needed to provide consistent suppression of bagrada bug in California.