Résumé
The successful parasitism of tens of thousands of species of endoparasitoid wasps is based on an interaction with a symbiotic polydnavirus that induces immunosuppression in their insect hosts. These natural enemies, which are particularly effective against Lepidoptera, contribute to crop protection by attacking phytophagous caterpillars. Investigating the effects of temperature on these biological control agents is of critical importance in the context of the current climate warming.Here we investigated the thermal performance of Hyposoter didymator, an endoparasitoid wasp carrying the HdIV polydnavirus. This wasp species parasitises the larvae of Spodoptera frugiperda, a major pest of agriculturally important crops. We exposed parasitised and unparasitised S. frugiperda larvae to three fluctuating temperature regimes, maintaining average temperatures of 20, 25, and 30 with ± 5°C over 24-hour cycles. Our results showed a high vulnerability of the parasitoid to the elevated temperature of 30°C. Parasitoid larval survival, host emergence, and subsequent cocoon formation were significantly impaired under this elevated temperature. In parallel, we observed a contrasting pattern in the response of non-parasitised S. frugiperda. Larval survival was negatively related to our experimental temperatures, but pupal survival was positively related to them.Overall, our results highlight the higher vulnerability of the polydnavirus-carrying parasitoid wasp to high temperatures compared to their host. This finding is critical for anticipating and mitigating potential changes in ecological interactions in the context of climate warming and highlights the importance of further research to inform adaptive pest management strategies.