RESISTANCE TO BACILLUS-THURINGIENSIS AFFECTS MATING SUCCESS OF THE DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE)

In laboratory choice tests, males from a colony of diamondback moth, Plutella xylostella (L.), resistant to Bacillus thuringiensis Berliner toxins mated fewer times than did males from a susceptible colony. Resistant and susceptible males did not differ in mating duration or ability to mate first with virgin females. Thus, the mating deficiency of resistant males was caused by reduced success in obtaining subsequent matings. Reduced mating success of resistant males is a fitness cost that may contribute to loss of resistance in the absence of exposure to toxins. Resistant females mated as frequently as susceptible females, suggesting that no change in female mating success was associated with resistance. We found no evidence for assortative mating between resistant and susceptible moths that would diminish the effectiveness of refuges in resistance management.