FEEDING-BEHAVIOR OF CRYIIIA-RESISTANT AND SUSCEPTIBLE COLORADO POTATOBEETLE (COLEOPTERA, CHRYSOMELIDAE) LARVAE ON BACILLUS-THURINGIENSIS TENEBRIONIS-TRANSGENIC CRYIIIA-TREATED AND UNTREATED POTATO FOLIAGE

Behavior of Bacillus thuringiensis tenebrionis-resistant and susceptib le Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae on cryIIIA-treated, B. thuringiensis tenebrionis-transgenic, and untreate d foliage was quantified. The behavior of resistant larvae was not aff ected by cryIIIA on treated leaves. Susceptible larvae exposed to cryI IIA-treated foliage spent approximate to 2% of the time feeding, where as susceptible larvae on untreated foliage spent 28% of the time feedi ng. Resting time for susceptible larvae on cryIIIA-treated foliage was nearly double resting time on untreated foliage. On cryIIIA-treated f oliage, 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. L arval position on the upper versus lower surfaces of leaves was not af fected by B. thuringiensis tenebrionis, and did not differ between res istant and susceptible strains. Our results suggest that larvae resist ant to formulated B. thuringiensis tenebrionis insecticides may remain susceptible to B. thuringiensis tenebrionis-transgenic plants that ex press high concentrations of toxin.