Early Season Parasitism of Cereal Aphids1 in Wheat Fields and Field Borders
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© 2019 Southwestern Entomological Society. Winter wheat, Triticum aestivum L., is the most widely grown crop in Oklahoma and typically is planted in early autumn and harvested in June. Wheat often is infested by insect pests, the most important of which are cereal aphids. The objective of the research was to determine the relationship between parasitism rates of cereal aphids on plants in the wheat field border versus in the wheat field. Aphid abundance in borders and fields was assessed by D-vac suction sampling. Three parasitoid species were reared from cereal aphids on sentinel plants in field borders and wheat fields during the 2-year study. Lysiphlebus testaceipes (Cresson) was the most abundant species, followed by Aphelinus nigritus Howard and Diaeretiella rapae (M'Intosh). There was no significant correlation for any species between the number of individuals emerging from aphids on sentinel plants in field borders before wheat was planted to the number emerging from sentinel plants in borders after emergence of wheat plants (r ranged from -0.12 to 0.22). Nor was there correlation for any species for the number of individuals emerging from sentinel plants in field borders after emergence of wheat to the number emerging at the same time from sentinel plants in adjacent wheat fields (r ranged from -0.08 to - 0.07). In a habitat there were significant correlations among species for the number of individuals emerging from sentinel plants (r ranged from -0.08 to 0.94). While the same parasitoid species forage for aphids in field borders as for cereal aphids in wheat fields, parasitism levels in borders did not reflect amounts in adjacent fields. This suggested that the amount of activity of cereal aphid parasitoids at field borders had minimal relationship to the amount of activity and hence to parasitism of cereal aphids in adjacent wheat fields.
author list (cited authors)
Elliott, N. C., Giles, K. L., Brewer, M. J., & Jessie, C. N.