Does rearing host alter host stage preference? Implications for mass rearing of two common pupal parasitoids of Drosophila suzukii

Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae) are pupal parasitoids capable of successfully developing on Drosophilidae species, including the invasive pest Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). Both parasitoids are considered potential biological control agents for managing D. suzukii. We conducted a long-term laboratory rearing study to assess whether different rearing host species, specifically D. suzukii and Drosophila melanogaster Meigen (Diptera: Drosophilidae), influence the parasitoids' preference for D. suzukii pupae at different developmental stages. In no-choice tests, T. drosophilae reared on either D. suzukii or D. melanogaster exhibited a preference for parasitizing younger D. suzukii pupae over older ones. In contrast, P. vindemiae reared on both host species did not show a significant difference in parasitism rates across D. suzukii pupal stages. Additionally, there were no significant differences in the performance of T. drosophilae and P. vindemiae after 10 generations of rearing on D. melanogaster when tested on D. suzukii pupae, compared to those reared on D. suzukii. These results suggest that long-term rearing on an alternative host does not alter the host stage preference of these parasitoids for D. suzukii.