Effects of Bacillus thuringiensis on adults of Cotesia plutellae (Hymenoptera : braconidae), a parasitoid of the diamondback moth, Plutella xylostella (Lepidoptera : plutellidae)

To complement existing information on the mortality of larvae of the wasp C otesia plutellae attacking moth caterpillars infected with Bacillus thuring iensis (Bt) we tested the direct and indirect effects of the bacterium on a dult wasp longevity and oviposition behaviour. In one experiment with femal e parasitoids, mean longevity (+/-SEM) was not significantly different betw een females exposed to Bt (1.98+/-0.08 days) and those not exposed (2.18+/- 0.13 days). In a second experiment with both males and females. Bt treatmen t did not significantly effect either male or female parasitoids exposed to Bt. To observe the possible effects of Bt on oviposition behaviour of C. p lutellae each of 10 females were given five larvae that had been treated wi th Bt and five untreated larvae at the same time. All parasitoids were obse rved to make oviposition attempts in both untreated and treated larvae Upon dissection of the host larvae, one or more C. plutellae eggs were found in each of the larvae in which a parasitoid attempted oviposition. There was no effect of Bt treatment on parasitoid oviposition. The mean number of ovi positions in treated larvae (4.3+/-0.3) was not significantly different fro m untreated larvae (4.7+/-0.2)