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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY BASED MANAGEMENT OF CEREAL APHIDS

Location: Wheat, Peanut and Other Field Crops Research

Title: Aphids and parasitoids in wheat and nearby canola fields in central Oklahoma

Authors
item Elliott, Norman
item Backoulou, Georges -
item Giles, Kristopher -
item Royer, Thomas -

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2014
Publication Date: March 1, 2014
Citation: Elliott, N.C., Backoulou, G.F., Giles, K.L., Royer, T.A. 2014. Aphids and parasitoids in wheat and nearby canola fields in central Oklahoma. Southwestern Entomologist. 39(1):23-28.

Interpretive Summary: In central Oklahoma, winter canola has recently become the primary rotational winter crop with wheat. Annual aphid pest outbreaks in canola have resulted in widespread insecticide applications. Insect parasitoids are natural enemies of aphid pests, which frequently suppress and maintain aphid pests in wheat below levels that will cause economic injury to the wheat crop. These parasitoids may move to canola due to the large numbers of aphids. In canola the parasitoids will likely be exposed to insecticides. The expansion of canola acres in Oklahoma could possibly disrupt biological control of cereal aphids in wheat by parasitoids if they prefer to colonize canola because of the abundance of aphids in the crop, and suffer extensive mortality as the result of more frequent use of insecticides in the crop. In this instance, canola could act as an ecological trap for L. testaceipes. We surveyed aphids and their parasitoids in wheat fields and nearby canola fields in central Oklahoma approximately at flowering time for canola. The purpose was to determine the relative abundance of aphids and parasitoids in each crop, and assess the potential for canola fields to act as an ecological trap for important parasitoids of aphids in wheat. We found that the parasitoids of aphids in canola and the parasitoids of aphids in wheat were different species. The results suggest limited potential for canola to attract parasitoids from wheat where canola could potentially serve as an ecological trap for the species. Hence, there is currently no cause for concern that canola will disrupt the naturally occurring biological control of aphids that currently occurs in wheat.

Technical Abstract: In central Oklahoma, winter canola has recently become the primary rotational winter crop with wheat. Annual aphid pest outbreaks in canola have resulted in widespread insecticide applications. Insect parasitoids, which frequently suppress aphids in nearby wheat, may move to canola due to the large numbers of aphids. These parasitoids will likely be exposed to insecticides. Lysephlebus testaceipes is the dominant parasitoid of aphid pests in wheat in Oklahoma and can frequently suppress and maintain aphid infestations below the economic injury level. The expansion of canola acres in Oklahoma could possibly disrupt biological control of cereal aphids in wheat if L. testaceipes prefers to colonize canola because of the abundance of aphids in the crop, and suffers extensive mortality as the result of more frequent use of insecticides in the crop. In this instance, canola could act as an ecological trap for L. testaceipes. We surveyed aphids and their parasitoids in wheat fields and nearby canola fields in central Oklahoma approximately at flowering time for canola. The purpose was to determine the relative abundance of aphids and parasitoids in each crop, and assess the potential for canola fields to act as an ecological trap for L. testaceipes. For aphids collected from canola fields D. rapae was the dominant parasitoid with parasitism rates ranging 2 to 27%. Aphelinus sp. also parasitized the cabbage aphid but was rare. Lysephebus testaceipes was not recovered from any species of aphid in canola fields in spite of the fact that it was abundant on greenbugs in nearby wheat fields with parasitism ranging from 3 to 43%. The results suggest limited potential for canola to attract L. testaceipes from wheat where canola could potentially serve as an ecological trap for the species.

Last Modified: 11/28/2014
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