title: Baseline susceptibility of the corn earworm (Lepidoptera: Noctuidae) to the Cry1Ab toxin from Bacillus thuringiensis.
abstract: Susceptibility to Cry1Ab toxin from Bacillus thuringiensis (Bt) was determined for 12 field populations of neonate corn earworm, Helicoverpa zea (Boddie), from the United States. Earworm larvae were exposed to artificial diet treated with increasing Bt concentrations, and mortality and growth inhibition were evaluated after 7 d. The range of variation in Bt susceptibility indicated by growth inhibition was very similar to that indicated by mortality. Although interpopulation variation in susceptibility to both proteins was observed, the magnitude of the differences was small (less than or equal to fivefold). These results suggest that the observed susceptibility differences reflect natural variation in Bt susceptibility among corn earworm populations rather than variation caused by prior exposure to selection pressures. Therefore, corn earworms apparently are susceptible to Bt toxins across most of their geographic range.
authors.affiliation: Department of Entomology, University of Nebraska, Lincoln 68583-0816, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Siegfried
authors.forename: T
authors.initials: T
authors.lastname: Spencer
authors.forename: J
authors.initials: J
authors.lastname: Nearman
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D001681:Biological Assay; D004731:Endotoxins; D006460:Hemolysin Proteins; D009036:Moths; D010572:Pest Control, Biological / Q000379:methods
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis