Annual and Seasonal Changes in Parasitism Rates by <i>Hadronotus Pennsylvanicus</i> (Hymenoptera: Scelionidae) on the Squash Bug <i>Anasa Tristis</i> (Hemiptera: Coreidae) in Squash Fields: Implications for Augmentative Releases

Abstract

This study evaluated parasitism rates by Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae) on the squash bug Anasa tristis DeGeer (Hemiptera: Coreidae) over a six-year period in squash fields in Maryland. From 2016–2021, 2226 wild squash bug egg masses were collected, 2180 (98.0%) A. tristis egg masses and 46 (2.0%) A. armigera egg masses. The mean (±SE) parasitism rate was 10.9 ± 0.16%. Yearly parasitism rates were significantly different with rates in 2017 and 2018 that were significantly lower than in 2019, 2020, and 2021. The significant difference in parasitism rates based on planting date was primarily due to the high parasitism rate observed in 2021. These results suggest that the use of augmentative releases early in the season could result in effective control by increasing parasitism earlier in the season and by causing the parasitism rate in the field to peak at a higher number late in the season.

Keywords

• <i>Gryon pennsylvanicum</i>
• biological control
• egg parasitism