Induction of thermotolerance in Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

Abstract

Temperature variations recorded during releases of the parasitoid Trichogramma brassicae Bezdenko used against the European corn borer, Ostrinia nubilalis Hubner (Lepidoptera), were simulated in the laboratory by applying single or double heat shock at 35 or 44°C for 6 h during the white pupal stage. Several biological characteristics were studied in the treated generation and its progeny. Induction of heat shock proteins was checked. Large (70-84-88-92 kDa) and small (25-26-28-29-32 kDa) heat shock proteins accumulated and persisted at least for I 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 sterility resulted from a 44°C treatment during the pupal susceptible period. A 35°C pretreatment had a protective effect with respect to a 2nd shock at 44°C, and this thermotolerance could be attributed to the persistence of heat shock proteins in the treated pupae during the period following the primary heat shock.