Towards integrated control of cereal aphids.
Changes in cereal farming practice over the last 15 years include increased insecticide use against cereal aphids, increased herbicide application and earlier sowing of winter cereals (Edwards, 1977; Graham-Bryce et al, 1979). In small plot experiments, pirimicarb application reduced aphid parasitoid numbers, and dimethoate reduced parasitoids and polyphagous predators. Polyphagous predators were influenced by weed removal, different species being affected in different ways. More cereal aphids were infected with fungal pathogens in weedy than in clean plots. Overwintering Sitobion avenae populations on early sown winter wheat supported high parasitoid populations, and both aphid and parasitoid numbers increased earlier in the season on early- than on late-sown crops. The importance of monitoring the effects of changing farming practice on the cereal fauna in order to predict future problems and devise integrated control procedures is stressed.