Monitoring bean leaf beetle (Cerotoma trifurcata) response to thiamethoxam soybean seed treatments

ABSTRACT The increased use of thiamethoxam seed treatments for controlling target pests such as the bean leaf beetle, Cerotoma trifurcata (Forster), suggests the need for methods to measure and monitor the development of resistance to these insecticides. Overwintering C. trifurcata were collected from alfalfa fields and used in early growth stage soybean studies to measure toxicity of thiamethoxam both in greenhouse experiments and laboratory bioassays involving exposure to treated foliage. Lethal and sub-lethal effects were detected in both greenhouse and lab bioassays. Lethal concentrations determined from laboratory assays will be compared with residues determined from field grown plants that were sampled through the early vegetative stages. Results will be presented and will provide a foundation for resistance monitoring and detection.