Suppression of Aphid Colonization by Insecticides: Effect on the Incidence of Potyviruses in Tobacco. T. P. Pirone, Department of Plant Pathology, University of Kentucky, Lexington 40546. B. Raccah, and L. V. Madden. Department of Virology, ARO, The Volcani Center, Bet Dagan, Israel; and Department of Plant Pathology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691. Plant Dis. 72:350-353. Accepted for publication 25 November 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0350.

The buildup of aphids (primarily Myzus persicae) in tobacco was prevented by the use of systemic insecticides in order to determine the relative importance of colonizing aphids in the spread of the nonpersistent tobacco etch and tobacco vein mottling viruses. Three pairs of plots, each containing about 3,300 tobacco plants, were compared; one member of each pair was treated with insecticide and the other served as a control. The experiment was done in three successive years. Insecticide treatment was extremely effective in suppressing aphid colonization and usually effective in reducing virus disease incidence and the absolute rate of disease increase (r’). In one pair of plots, however, r’ was significantly increased in 1983, unaltered in 1984, and significantly reduced in 1985. Ecological and seasonal factors that affect the numbers and movement of aphids appear to play a major role in determining the relative importance of colonizing aphids as agents of spread of nonpersistent viruses.