Effect of Oil and Insecticide on Epidemics of Potyviruses in Watermelon in Florida. Susan E. Webb, University of Florida, Central Florida Research and Education Center, 5336 University Avenue, Leesburg 34748. Stephen B. Linda, University of Florida, Department of Statistics, Gainesville 32611. Plant Dis. 77:869-874. Accepted for publication 8 June 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0869.

The effect of JMS stylet oil and/or endosulfan on the incidence and spread of potyviruses in watermelon in the autumn of 1988 and the spring growing seasons of 1989 and 1990 was determined. The incidence of virus-infected plants reached 50% 5–7 days later in oil-treated plots each year, and the maximum rate of virus spread was reduced in 1990. In 1990, the average damage rating of melons from plots not receiving oil was significantly higher than the rating of melons from oil-treated plots. Weights of individual melons from oil-treated plants were significantly lower, however, and at the earliest stages of bloom, 6 wk after planting, there were fewer flowers on oil-treated plants. Endosulfan did not affect virus spread. Oil may be useful for delaying first infections in the spring crop when inoculum sources are limited.