A comparative assessment of the effects of Bt plants and a pyrethroid insecticide on the life parameters of a parasitoid

A comparative assessment of the effects of Bt plants and a pyrethroid insecticide on the life parameters of a parasitoid Xiaoxia Liu, Mao Chen, Anthony M. Shelton* Department of Entomology, Cornell University/New York State Agricultural Experiment Station (NYSAES)

The effects of Cry1Ac broccoli and a pyrethroid insecticide on the life parameters of a parasitoid, Diadegma insulare, were studied. The results showed that D. insulare could not discriminate between resistant and susceptible genotypes of its host, Plutella xylostella, nor Cry1Ac and normal broccoli plants with different genotypes of P. xylostella. The parasitism rate, developmental period, pupal and adult weight of D. insulare developed from the Cry1Ac-resistant P. xylostella larvae fed on Cry1Ac broccoli plants were not significantly different from those that developed from non-Bt broccoli plants. Female D. insulare emerged from Cry1Ac-resistant P. xylostella that fed on Cry1Ac plants could successfully parasitize P. xylosetella larvae. The life parameters of F2 D. insulare from Cry1Ac broccoli were not significantly different from non-Bt broccoli. When D. insulare were supplied with pyrethroid-resistant P. xylostella larvae that fed on pyrethroid-treated broccoli plants, the parasitism rate was significantly decreased in comparison to an untreated normal plant. Our results indicate that Cry1Ac plants are safer to the parasitoid than a pyrethroid treated plant.