All protoxin mixtures demonstrated significant synergistic toxicity activity against C. suppressalis,
with values of 1.6- to 11-fold higher toxicity than the theoretical additive effect. Surprisingly, all but
one of the Bt protoxin mixtures were antagonistic in toxicity to S. inferens. In mortality-time response
experiments, S. inferens demonstrated increased tolerance to Cry1Ab and Cry1Ac compared to C. suppressalis
when treated with low or high protoxin concentrations. The data indicate