Field Populations of Three Grain Aphid Species in Western Oregon1

Abstract

Barley seeded early in the spring had smaller populations of the English grain aphid, Macrosiphum avenae (F.), and larger populations of Acyrthosiphon dirhodum (Walker) than fields seeded later in the spring in western Oregon. Populations of these 2 species and Rhopalosiphum padi (L.) established on plants at a later growth stage in early-planted plots of barley than in late-planted plots. During 2 winters of study, M. avenae was found on winter grain plants, A. dirhodum was abundant on orchardgrass, and R. padi was the most abundant grain aphid on several grain and grass plants.