A comparative assessment of the effects of Bt plants and a pyrethroid insecticide on Coleomegilla maculata (Coleoptera: Coccinellidae)

The effects of Cry1Ac broccoli and a pyrethroid insecticide on the life parameters of the predator, Coleomegilla maculataiColeoptera: Coccinellidaej, were studied. The results showed that C. maculata could not discriminate between resistant (Cry1Ac or pyrethroid) and susceptible genotypes of its host, Plutella xylostella, nor Cry1Ac and normal broccoli plants with different genotypes of P. xylostella. The life parameters of C. maculata fed on the Cry1Ac-resistant P. xylostella larvae on Cry1Ac broccoli plants were not significantly different from those on non-Bt broccoli plants. However, the pyrethroid was very toxic to the predator and the adult and larvae of the predator could not survive on a pyrethroid-treated plant. Our results indicate that Cry1Ac plants are safer to C. maculata than a pyrethroid-treated plant.