Corn flea beetle population densities and Stewart’s wilt incidence were monitored at a range of locations that provided different overwintering survivorship of flea beetles. Yellow sticky traps, sweep samples, and insect counts on plants were used to assess population densities. Results indicated flea beetle densities are able to rebuild after a single mild winter. Incidence of Stewart’s wilt followed patterns of flea beetle densities. Disease incidence in each plot was significantly correlated to flea beetle densities, and this relationship might be used in making decisions on the use of foliar insecticides. We propose a preliminary threshold of 5 beetles per trap per day from seedling emergence through the V2-V3 stages. In 31 plots where beetle densities were < 5 per trap per day, Stewart’s wilt incidence was low (<5%) in 26 plots (81%). Estimates of beetle infectivity (the portion of the population testing positive for Erwinia stewartii) with beetle density estimates may predict more accurately the incidence of Stewart’s wilt. A proposed threshold of 1 infective beetle per trap per day provides slightly greater accuracy than using a threshold of 5 beetles per trap per day. More work is required to determine the potential value of using infectivity estimates in the field to make improved insect control decisions.
Species 1: Coleoptera Chrysomelidae Chaetocnema pulicaria (Corn Flea Beetle)
Keywords: Stewart's wilt, sweet corn
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