Evaluating augmentative biological control for squash bug using releases of egg parasitoid, Hadronotus pennsylvanicus

The squash bug, Anasa tristis (Hemiptera: Coreidae), is a serious pest of summer squash and pumpkins (Cucurbita pepo) across the United States. Conventional growers commonly use broad spectrum insecticides to manage squash bug, however organic growers lack these effective chemical tools and must rely on alternative management strategies. Biological control of squash bug 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 field releases of H. pennsylvanicus on organic farms in southwest Virginia to test whether A. tristis egg parasitism would improve at parasitoid release sites. Farms chosen as release sites were paired with separate no-release farms where no parasitoids were released. 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 deployment, biweekly collections of squash bug eggs were conducted at release and non-release sites. In both years, we found greater parasitism rates of A. tristis eggs collected at Virginia release sites compared to no-release sites. While all eggs collected at release and no-release sites before parasitoid deployment 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.