Since 1995, almost all potato growers have relied on imidacloprid for Colorado potato beetle (Leptinotarsa decemlineata) control. Thiamethoxam, another neonicotinoid insecticide, became available for commercial use in 2002, providing another effective control agent but also concern for additional resistance development. Populations from across the United States were bioassayed for both imidacloprid and thiamethoxam resistance in 2002 and 2003. In addition, laboratory populations have been selected with imidacloprid and thiamethoxam to increase resistance to each compound. High levels of resistance were found outside of Long Island, NY, with beetles from commercial sites in Delaware and Pennsylvania being greater than 100 fold and 25 fold resistant to imidacloprid, respectively, compared to a susceptible strain. Meanwhile, populations in the Great Lakes region remain highly susceptible to both compounds. Resistance to imidacloprid was highly correlated with resistance to thiamethoxam, although resistance to thiamethoxam was at a lower level than resistance to imidacloprid in all cases. Monitoring of resistance and cross resistance is a critical part of resistance management.
Species 1: Coleoptera Chrysomelidae Leptinotarsa decemlineata (Colorado potato beetle)
Keywords: neonicotinoid insecticides, resistance management
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