EFFECT OF IMIDACLOPRID ON NONFLIGHT MOVEMENT OF RHOPALOSIPHUM-PADI AND THE SUBSEQUENT SPREAD OF BARLEY YELLOW DWARF VIRUS

The bird cherry-oat aphid (Rhopalosiphum padi) is an important vector of the barley yellow dwarf luteovirus, BYDV-PAV-IL. Insecticides used to reduce the abundance of the vector on small grains can result in an increase in aphid activity and a subsequent increase in disease incid ence. The transmission characteristics of viruliferous wingless (nymph s and apterous adults) R. padi after access to oats treated with diffe rent rates of imidacloprid, a seed-treatment insecticide, were compare d. After access to treated plants, aphid fecundity was reduced and aph ids walked and fed atypically and often abandoned the host plant. The spread of BYDV from a focus of infestation to individual imidacloprid- treated oats planted in a grid was followed by observation of symptoms and by enzyme-linked immunosorbent assay. Aphids transmitted the viru s to both treated and untreated plants, but the percentage of infected insecticide-treated seedlings was one-half that of untreated seedling s.