Trichogramma pratissolii Querino & Zucchi (Hymenoptera, Trichogrammatidae) performance in Anagasta kuehniella (Zeller) (Lepidoptera, Pyralidae) eggs affected by Bacillus thuringiensis Berliner

Abstract

This work was carried out to detect at laboratory the possible side-effects provoked by Bacillus thuringiensis (Bt) strains on egg parasitoid Thichogramma pratissolii and its progeny. Six strains of Bt E-3, E-10, E-15, E-16, E-19, E-20 and Bt kurstaki were assayed in honey drop to stimulate the feeding of the parasitoids in each treatment (1:1) and pure honey as check treatment and offered simultaneously displays with eggs of the host alternative Anagasta kuehniella. The experiment was maintained in a climatized chamber at 25 ± 1°C, RH 70 ± 10% and photofase of 14hours. The survival, daily parasitism, accumulated parasitism and total parasitism and also the progeny's emergence and sexual ratio were analyzed. Bt isolates did not affect parasitism, sexual ratio and longevity, but some of them (E-3, E-10, E-16 e E-20) affected parasitoid progeny. In field conditions this could imply in more parasitoid liberations to the expected results. Otherwise, parasitism acceleration verified in all treatments suggest that when T. pratissolii adults pass on some extern pressure (stress) they parasitize as soon as possible to assure progeny survival. The interaction Bt + T. pratissolii may increase the parasitoid preformance in the field, mainly when a rapid decrease of pest population is desirable.