Toxic and Behavioral Effects to Carabidae of Seed Treatments Used on Cry3Bb1- and Cry1Ab/c-Protected Corn

Most transgenic corn seed is now treated with systemic neonicotinoid insecticides. To address potential direct nontarget effects of these combined technologies, 16 Carabidae species from 10 genera (Agonum, Amara, Anisodactylus, Bembidion, Chlaenius, Harpalus, Patrobus, Poecilus, Pterostichus, and Scarites) Þeld-collected from corn were directly exposed to Bacillus thuringiensis (Bt) Cry toxin-laden pollens and seed treatments in feeding and deÞned-dose bioassays. All adults readily fed on Þeld or sweet corn pollens that expressed coleopteran-speciÞc Cry3Bb1 or lepidopteran-targeting Cry1Ab/c, and no signiÞcant toxicity was observed. Adult survivorship ranged from 47 d for the predator Pterostichus melanarius (Illiger) to a year for the more omnivorous Scarites quadriceps Chaudoir, feeding solely onpollen containing 30Ð90 gCry3Bb1/g andwater. In contrast, commercial doses of neonicotinoid seed treatments (imidacloprid, thiamethoxam, or clothianidin) elicited nearly complete mortality for 18 carabid species in 4-d bioassays containing corn seedlings. Carabid consumption of fungicide-only (ßudioxonil plus mefenoxam) seed treatments was generally observed within 1 d, comparedwith a 2-d latency on neonicotinoid treatments, suggesting an antifeedant effect of the insecticide. In microcosm bioassays containing a corn seedling and Þve prey, clothianidin seed treatments killed adult western corn rootworm, Diabrotica virgifera virgifera LeConte and S. quadriceps, although the smaller Harpalus pensylvanicus (DeGeer) was more tolerant. We conclude that the neonicotinoid/fungicide seed treatments, and not Cry3Bb1 or CryIAb/c, are a major direct mortality factor for ground beetles. Field studies are needed to determine population and community level effects on Carabidae when these transgenic and seed-treatment technologies are combined.