Contact and oral toxicity to honey bees (Apis mellifera) of agents registered for use for sweet corn insect control in Ontario, Canada

Abstract

Assays were conducted to compare direct and residual contact and oral toxicities to honey bees of sweet corn insecticides and of Bt-sweet corn. Direct contact assays focusing on LC50 determined that technical grade clothianidin was most toxic, > carbofuran, > imidacloprid = spinosad, > lambda-cyhalothrin, > Bacillus thuringiensis. In residual contact assays, forager age bees were exposed to treated non-transgenic sweet corn tassels. Carbofuran treated tassels caused significant mortality up to 2 and 3 days after treatment (DAT) in 2002 and 2003, respectively. Lambda-cyhalothrin treated tassels had no impact on honey bees in 2002; in 2003, their toxicity was significantly higher than the untreated control tassels for 1 DAT. In both years, spinosad, imidacloprid and clothianidin or Bt-sweet corn tassels had no impact on honey bee mortality. Pollen collected from insecticide field treated corn and fed to honey bees had no impact on mortality. © INRA/DIB-AGIB/ EDP Sciences, 2005.