Augmentative biological control for squash bug using the egg parasitoid, Hadronotus pennsylvanicus

Authors: Boyle, Sean; SALOM, SCOTT - Virginia Polytechnic Institution & State University; SCHULTZ, PETER - Virginia Polytechnic Institution & State University; LOPEZ, LORENA - Virginia Polytechnic Institution & State University; Weber, Donald; KUHAR, THOMAS - Virginia Polytechnic Institution & State University

Submitted to: Environmental Entomology/Population Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2023
Publication Date: 8/14/2023
Citation: Boyle, S.M., Salom, S., Schultz, P., Lopez, L., Weber, D.C., Kuhar, T.P. 2023. Augmentative biological control for squash bug using the egg parasitoid, Hadronotus pennsylvanicus. Environmental Entomology/Population Ecology. https://doi.org/10.1093/ee/nvad079.
DOI: https://doi.org/10.1093/ee/nvad079

Interpretive Summary: The squash bug is a serious insect pest of summer squash across the United States. Squash bugs inflict damage by feeding on plant leaves, stems, and fruits, leading to significant reductions in fruit yield and overall economic losses for growers. To date, farmers have few useful tools to minimize squash bug damage in their summer squash crop, and resort to broad-spectrum insecticides for squash bug control. While this use of insecticides helps lower squash bug numbers, it often has negative side effects on the environment and important beneficial insect species like pollinators. Alternatives such as biological control, the use of natural enemies to control pests, are not well studied for squash bugs. We reared and conducted releases of a known squash bug natural enemy, the native parasitoid wasp Hadronotus pennsylvanicus, which attacks squash bug eggs. In June 2020 and 2021, we released parasitoid wasps on organic farms growing summer squash in southeastern Virginia. In both years, our data show evidence of increased egg parasitism at research sites where the wasps were released compared to sites where wasps were not released. This promising new method for controlling squash bugs will be of interest to vegetable farmers, pest managers, and researchers involved with squash and related cucurbit crops.

Technical Abstract: The squash bug, Anasa tristis (Hemiptera: Coreidae, is a serious pest of cucurbit crops across the US, especially within summer squash (Cucurbita pepo) systems. Conventional growers most commonly use broad spectrum insecticides to manage squash bugs, however organic growers lack these effective chemical tools and therefore rely on alternative management strategies. Biological control of squash bugs is largely understudied, specifically the potential of its natural enemy, Hadronotus pennsylvanicus (Hymenoptera: Scelionidae), as an augmentative biological control agent. For this reason, we performed early-season field releases of H. pennsylvanicus on organic farms in southeastern Virginia to test whether this would improve A. tristis egg parasitism. We chose organic farms growing summer squash as release sites and paired each site with a no-release site. Parasitoids were reared in the lab and deployed as parasitized egg masses at a rate of 2-3 females wasps per plant in June 2020 and 2021. Following H. pennsylvanicus deployment, we found greater parasitism rates of A. tristis eggs compared to no-release sites. Before parasitoid deployment, host eggs collected at release and no-release sites displayed low levels of H. pennsylvanicus parasitism. Eggs from release sites were significantly more parasitized than eggs from no-release sites within two weeks post-deployment. Our two-year study demonstrates that the releases of lab-reared H. pennsylvanicus can increase A. tristis egg parasitism rates and subsequently decrease successful nymph hatch rates in early summer squash plantings.