Effects of host switching and successive multigenerational rearing of the parasitoid Eretmocerus corni (Hymenoptera: Aphelinidae) on host preference and adaptation

Background: The adaptive strategies of parasitoids against different hosts may evolve under successive multigenerational rearing in alternative hosts; therefore, it is crucial to validate the maintenance and optimization of parasitoid adaptations to target pests during mass rearing. Eretmocerus corni Haldeman (Hymenoptera: Aphelinidae) is a biological control agent for managing whitefly pests. Here, we investigated the effects on preference and adaptation of adult E. corni transferred from its original host, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), to a new host, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), through successive multigenerational rearing on B. tabaci nymphs. Results: The results of the choice assays showed that for the first five generations, the parasitoids showed a clear preference for the original rearing host T. vaporariorum nymphs. However, after 15 generations of rearing on B. tabaci nymphs, there was a preference for B. tabaci nymphs compared to T. vaporariorum nymphs. No-choice assays showed that there was no significant increase in the number of B. tabaci nymphs parasitized and total mortality in all generations, but the number of T. vaporariorum nymphs parasitized and total mortality were both significantly higher in the control than the10th and 15th generations. When E. corni parasitized T. vaporariorum nymphs, the developmental time of the 1st generation offspring was significantly shorter than that of other generations. Host feeding, offspring female ratio and emergence rate did not differ among generations or between host species. Conclusion: Our analyses showed that successive rearing of E. corni on an alternative host was able to enhance the preference for that host. However, despite this increase in preference, the developmental suitability did not change significantly among generations. This study provides fundamental information for understanding the parasitism performance of E. corni across different whitefly hosts over multiple generations.