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Flea Beetle and the Incidence of Stewart's Wilt in New York Sweet Corn 2000

Project Leaders: Mike Hoffmann, Tom Kuhar, and Lee Stivers

Abstract:

Stewart’s bacterial wilt is an important disease of sweet corn in the northeastern United States. In 2000, we initiated a two-yr study of the ecology and management of corn flea beetle and Stewart’s wilt in New York. To investigate the effect of different cultural practices on corn flea beetles, we monitored emergence of CFB from various plots at the NYCRF farm in Batavia, NY. To investigate colonization patterns of CFB, we sampled the relative abundance of beetles in and around borders of 10 sweet corn fields in central and western New York. Sampling methods included sticky cards placed inside and outside of field borders and at one location, vacuuming and sweep netting vegetation. To better understand the seasonal biology (phenology) of CFB, we sampled beetle populations in >20 sweet corn fields in western and central NY. To assess the incidence of Stewart’s wilt disease in sweet corn relative to various agronomic and edaphic parameters, we assessed >100 fields or research plots from 8 counties in western and central NY. These data along with various environmental parameters collected from each site were entered into a database, which we will use to construct a multiple regression model to predict relative risk of disease infection. CFB were active and abundant in early May in various habitats in and around cornfields. CFB were active in corn from May to October with multiple (2-4) population peaks occurring throughout the season. Population peaks occurred approximately 28 days apart, which coincides with the CFB development time it takes to complete a single generation. CFB exceeded threshold (6 beetles/100 plants) in all fields sampled in 2000. CFB population levels were not significantly different among early vs. mid-season vs. late plantings of corn. Weekly catch of CFB on sticky cards was highly correlated with CFB counts on plants. The Stewart’s wilt temperature index forecasted a light year for the disease in western New York and a forecast of absent or nearly so for central New York counties. Results of the field surveys indicated that Stewart’s wilt incidence was not different between fields planted in western NY and central NY.