Host finding behavior of the egg parasitoid, Gryon pennsylvanicum Ashmead (Hymenoptera: scelionidae)

Authors: Hu, Jing - Hu; Zhang, Aijun; Cornelius, Mary; Vinyard, Bryan

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2021
Publication Date: 4/28/2021
Citation: Hu, J.S., Zhang, A., Cornelius, M.L., Vinyard, B.T. 2021. Host finding behavior of the egg parasitoid, Gryon pennsylvanicum Ashmead (Hymenoptera: scelionidae). Biocontrol Science and Technology. https://doi.org/10.1080/09583157.2021.1910203.
DOI: https://doi.org/10.1080/09583157.2021.1910203

Interpretive Summary: The squash bug, Anasa tristis is a serious pest of cucurbit crops. The egg parasitoid, Gryon pennsylvanicum is the primary parasitoid of the squash bug and has been considered as a biological control agent. Chemicals that mediate interspecific interactions are known as kairomones. In the present study, we conducted both laboratory and greenhouse bioassays to determine the effects of kairomones emitted by squash bugs on the host searching behavior of the egg parasitoid. Chemicals were extracted from squash bug eggs, unmated females and males, and mated females and males. Of the five kairomone extracts, the egg extract was the most attractive to the parasitoids in laboratory assays. Further greenhouse bioassays confirmed that application of kairomones could result in a significantly higher rate of parasitism of squash bug eggs. The promising result from this study highlights the potential application of kairomones in enhancing the efficacy and effectiveness of biological control programs and should be of interest to growers and pest control professionals.

Technical Abstract: The squash bug, Anasa tristis (De Geer) is a serious pest of cucurbit crops. The egg parasitoid, Gryon pennsylvanicum (Ashmead), is the primary parasitoid of the squash bug and has been considered as a biological control agent. In the present study, we conducted both laboratory and greenhouse bioassays to determine the effects of kairomones emitted by A. tristis on the host searching behavior of G. pennsylvanicum. Chemicals were extracted from A. tristis eggs, unmated females and males, and mated females and males. The laboratory bioassays showed that the host finding behavior of female parasitoids could be significantly influenced by extracts from eggs, mated female and male adults, and unmated female and male adults of A. tristis. Of the five kairomone extracts, the egg extract was the most attractive to the parasitoids in laboratory assays. Further greenhouse bioassays confirmed that application of kairomones could result in a significantly higher rate of parasitism of A. tristis by G. pennsylvanicum, compared to the negative control without kairomone application. The non-polar kairomone compounds extracted by hexane were more effective in the host searching, compared to the polar kairomone compounds extracted by ethanol. Parasitoids used less time to identify and recognize hexane-kairomone extracts than ethanol-kairomone extracts and spent more time to explore on the hexane-kairomone extract spot. The promising result from this study highlights the potential application of kairomones in enhancing the efficacy and effectiveness of biological control programs and should be of interest to growers and pest control professionals.