Aphids1and Parasitoids2in Wheat and Nearby Canola Fields in Central Oklahoma

Abstract

Abstract. In central Oklahoma, winter canola (Brassica napus L.) has recently become the primary rotational winter crop with wheat (Triticum aestivum L.). Annual aphid pest outbreaks in canola have resulted in widespread application of insecticide. Insect parasitoids, which frequently suppress aphids in nearby wheat, may move to canola because of large numbers of aphids. These parasitoids probably will be exposed to insecticide. Lysiphlebus testaceipes Cresson 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 acreage in Oklahoma might disrupt biological control of cereal aphids in wheat if L. testaceipes prefers to colonize canola because of the abundance of aphids and many die as a result of more frequent use of insecticide in canola. In this case, canola could act as an ecological trap for L. testaceipes. We surveyed aphids and their parasitoids in wheat and nearby canola fie...