Simulation of Integration of Bacillus thuringiensis and the Parasitoid Cotesia plutellae (Hymenoptera: Braconidae) for Control of Susceptible and Resistant Diamondback Moth (Lepidoptera: Plutellidae)

We used computer simulations to better understand how to combine the microbial insecticide Bacillus thuringiensis Berliner and the parasitoid Cotesia plutellae Kurdjurnov to control diamondback moth, Plutella xylostella (L.). The simulations incorporated potential for the evolution of moth resistance to Bacillus thuringiensis with Bacillus thuringiensis-parasitoid-pest interactions. We considered the effects of pest immigration, pesticide refuge, and pesticide dose on diamondback moth control and resistance development by diamondback moth. Four major conclusions were drawn. First, C. plutellae and B thuringiensis could be used effectively to control diamondback moth. Second, the use of parasitoids such as C. plutellae could slow the evolution of pesticide resistance by decreasing the number of generations in which pesticide treatment is required. Third, parasitoids could be complementary to refuges from pesticides, with parasitoids maintaining control of a pest while refuges slow the development of resistance to the pesticide by the pest. Fourth, in conjunction with the use of parasitoids, high dose or low dose strategies have similar consequences on pest density over long periods. However, unless there is substantial immigration of susceptible individuals into the pest population or some type of pesticide refuge, a low dose strategy is better for controlling pests.