Effects of Insecticides Applied in the Field on Incidence of Aphid-borne Viruses in Cultivated Strawberry. R. H. Converse, Research Plant Pathologist, United States Department of Agriculture, Agricultural Research Service, Oregon State University, Corvallis 97331. M. T. Aliniazee, Professor of Entomology, Department of Entomology, Oregon State University, Corvallis 97331. Plant Dis. 72:127-129. Accepted for publication 16 July 1987. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/PD-72-0127.

Four pyrethroid insecticides and oxydemetonmethyl were evaluated in field spray application tests for ability to reduce the incidence of aphids and aphid-borne viruses in a field plot of Totem strawberry plants over a 2-yr period at Corvallis, OR. Ninety-four percent of the virus infection occurred during the second year of the test. Three pyrethroids (cypermethrin, permethrin, and fenvalerate) and oxydemetonmethyl significantly reduced aphid-borne virus incidence to 44–63% of the adjoining unsprayed plots at the end of the second growing season, whereas the pyrethroid bifenthrin gave a virus incidence that was not significantly different from that of the unsprayed treatment. Strawberry mild yellow-edge (SMYEV), a luteovirus, was present in 97% of the virus-infected strawberry plants and was the only virus detected in 88% of those plants. All insecticides caused a highly significant reduction of populations of the SMYEV vector aphid, Chaetosiphon fragaefolii, compared with the unsprayed plots in the second growing season. There was no significant association between efficacy of insecticides in reducing aphid populations and virus incidence, however, suggesting that properties of these insecticides other than aphid kill may have influenced virus incidence.