Induction of thermotolerance in Trichogramma brassicae (Hymenoptera : Trichogrammatidae)

Temperature variations recorded during releases of the parasitoid Trichogra mma brassicae Bezdenko used against the European corn borer, Ostrinia nubil alis Hubner (Lepidoptera), were simulated in the laboratory applying single or double heat shock at 35 or 44 degrees C for 6 h during the white pupal stage. Several biological characteristics were studied in the treated gener ation and its progeny. Induction of treat shock proteins was checked. Large (70-84-88-92 kDa) and small (25-26-28-29-32 kDa) heat shock proteins accum ulated and persisted at least for 1 d in treated pupae. Consistent with the biologically negative effects of high temperatures recorded in the field, we observed that increased pupal mortality, decreased fecundity, and male s terility resulted from a 44 degrees C treatment during the pulpal susceptib le period. A 35 degrees C pretreatment had a protective effect with respect to a 2nd shock at 44 degrees C, and this thermotolerance could be attribut ed to the persistence of heat shock proteins in the treated pupae during th e period following the primary heat shock.