Consequences of acclimation on survival and reproductive capacities of cold-stored mummies of Aphidius rhopalosiphi (Hymenoptera: Aphidiinae)

The cold storage of parasitoid mummies is a crucial point during mass production of parasitoids for aphid control in wheat, Triticum spp. In this study, the effect of acclimation to cold before storage of mummies containing Aphidius rhopalosiphi DeStefani-Peres (Hymenoptera: Braconidae: Aphidiinae) was evaluated on survival, sterility, and fecundity of parasitoids. Groups of 1-d-old and 3-d-old mummies were stored at -5 degrees C for 10 d without acclimation or after one of five different acclimation treatments. One-day-old and 3-d-old mummies contain prepupa and postmetamorphosis but not yet sclerotinized adult parasitoids, respectively. The offspring and sex ratio of stored parasitoids were compared with a control that was left at rearing temperatures (20 degrees C). Without acclimation, two-thirds of the parasitoids died during storage, for both ages of mummies tested. For stored 1-d-old mummies, subsequent survival increased under progressive exposure to low temperatures and reached 67.3% after 480 min of acclimation. In the same way, percentage of male sterility decreased with acclimation duration, whereas female fecundity increased. For stored 3-d-old mummies, subsequent survival improved with the duration of the acclimation treatment, but not male sterility and female fecundity.