Environmental Entomology (2018) 47, 1451-1458

Mary L. Cornelius, Jing S. Hu and Bryan T. Vinyard (2018)
Comparative study of egg parasitism by Gryon pennsylvanicum (Hymenoptera: Scelionidae) on two squash bug species Anasa tristis and Anasa armigera (Hemiptera: Coreidae)
Environmental Entomology 47 (6), 1451-1458
Abstract: This study evaluated how the size of the egg mass and the parasitoids prior exposure to eggs influenced parasitism rates by Gryon pennsylvanicum Ashmead (Hymenoptera: Scelionidae) on egg masses of two squash bug species, Anasa tristis DeGeer and Anasa armigera Say (Hemiptera: Coreidae). G. pennsylvanicum is the primary egg parasitoid of A. tristis. There were no published reports available on egg parasitism of A. armigera. In choice tests, there was no difference in host acceptance by G. pennsylvanicum of egg masses of the two squash bug species. In no-choice tests, overall parasitism rates were significantly higher on A. armigera egg masses than on A. tristis egg masses. Naive parasitoids had significantly higher parasitism rates than experienced parasitoids on egg masses of both squash bug species. In a comparison of parasitism rates of field-collected and laboratory-tested A. tristis egg masses of different sizes, parasitism rates were similar in the field and in the laboratory, with the exception of egg masses with > 25 eggs. Only 17.9% of eggs were parasitized in the laboratory, compared with 36.4% in the field. Results of this study indicate that transient egg limitation prevents G. pennsylvanicum from ovipositing in every available host egg in large squash bug egg masses. The low parasitism rate of G. pennsylvanicum on large egg masses may limit its effectiveness as a biological control agent of squash bugs.
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Database assignments for author(s): Mary L. Cornelius

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Anasa tristis	Squash/pumpkin (Cucurbita)	U.S.A. (NE)
	Anasa armigera	Squash/pumpkin (Cucurbita)	U.S.A. (NE)
Hadronotus pennsylvanicus (parasitoid)	Anasa tristis	Squash/pumpkin (Cucurbita)	U.S.A. (NE)
Hadronotus pennsylvanicus (parasitoid)	Anasa armigera	Squash/pumpkin (Cucurbita)	U.S.A. (NE)