Effects of the Cry1Ac toxin ofBacillus thuringiensisonMicroplitis mediator, a parasitoid of the cotton bollworm,Helicoverpa armigera.

Interactions between the cotton bollworm,Helicoverpa armigera(Hübner) (Lepidoptera: Noctuidae), its larval parasitoidMicroplitis mediator(Haliday) (Hymenoptera: Braconidae), and the Cry1Ac toxin ofBacillus thuringiensisBerliner were evaluated under laboratory conditions. The growth ofH. armigeralarvae was delayed and its pupal rate and pupal weight decreased when they were fed on a diet containing Cry1Ac toxin. Due to the lowered growth rate of the host larvae, the time available for parasitization ofH. armigerabyM. mediatorincreased when the host larvae were reared on a diet containing Cry1Ac toxin at concentrations of 0.5, 1, 2, and 4 µg g−1. The longevity of female and male parasitoids was not significantly affected when newly emerging wasps fed on honey solutions containing three different concentrations of Cry1Ac toxin (125, 250, and 500 µg ml−1). When female parasitoids were fed on honey solutions containing Cry1Ac, their offsprings’ egg and larval development period, pupal weight, length of pupation, adult weight, and adult longevity did not change significantly in most of the treatments compared with controls. When the female parasitoids parasitized host larvae that had been fed on a diet containing 0.5, 1, 2, 4, and 8 µg g−1 Cry1Ac toxin, their offsprings’ eggs and larvae were significantly delayed. Their pupal weight, adult weight, and adult longevity were also significantly less than controls. [ABSTRACT FROM AUTHOR]