Feeding behavior of cryIIIA-resistant and susceptible Colorado potato beetle (Coleoptera: Chrysomelidae) larvae on Bacillus thuringiensis tenebrionis-transgenic cryIIIA-treated and untreated potato foliage

Behavior of Bacillus thuringiensis tenebrionis-resistant and susceptible Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae on cryIIIA-treated, B. thuringiensis tenebrionis-transgenic, and untreated foliage was quantified. The behavior of resistant larvae was not affected by cryIIIA on treated leaves. Susceptible larvae exposed to cryIIIA-treated foliage spent approximate to 2% of the time feeding, whereas susceptible larvae on untreated foliage spent 28% of the time feeding. Resting time for susceptible larvae on cryIIIA-treated foliage was nearly double resting time on untreated foliage. On cryIIIA-treated foliage, resistant larvae spent 11% of the time feeding, significantly longer than fur susceptible larvae. The behavior of both resistant and susceptible larvae on B. thuringiensis tenebrionis transgenic leaves was similar to that of susceptible larvae on cryIIIA-treated leaves. Larval position on the upper versus lower surfaces of leaves was not affected by B. thuringiensis tenebrionis, and did not differ between resistant and susceptible strains. Our results suggest that larvae resistant to formulated B. thuringiensis tenebrionis insecticides may remain susceptible to B. thuringiensis tenebrionis-transgenic plants that express high concentrations of toxin.