Fitness costs of resistance to Bacillus thuringiensis in the Indianmeal moth, Plodia interpunctella

Genetic changes in insects that result in insecticide resistance can also a ffect their fitness. Here, we report measurements of development time and s urvival of the Indianmeal moth, Plodia interpunctella (Hubner), to compare the relative fitness of Bacillus thuringiensis (Bt)-susceptible and -resist ant colonies. Measurements of larval development time and survival indicate d that a fitness cost was associated with resistance to Bt in some Bt-resis tant colonies but not others. Comparisons of geographically different popul ations revealed inherent differences in development time and survival. In m ost cases, Bt-resistant moths suffered no disadvantage when feeding on a Bt -treated diet. In many cases, the development of Bt-resistant moths on Bt-t reated diet was slower than the unselected moths on untreated diet, but it is unclear whether these differences would affect the successful mating of susceptible and resistant moths.