Generation-dependent fitness of the parasitoid wasp Trichogramma brassicae (Hymenoptera: Trichogrammatidae) in laboratory and insectarium condition

Deep understanding of biological and behavioral characteristics of trichogrammatid wasps, helps us for better and more efficient rearing of these parasitoids. In the current study, Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was reared on Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) for several generations and the effect of long-term rearing of the parasitoid on some of its attributes like parasitism capability, emergence rate, sex ratio, and wingless rate of adults was determined in both laboratory and insectarium conditions. The laboratory investigation showed that long-term rearing decreased fitness of the parasitoid, so that, parasitism rate and adult emergence rate decreased. By contrast, sex ratio and number of wingless individuals increased with increasing generations. Our results in insectarium were a little different. However, adult emergence rate had significant difference and trichocards quality decreased with increasing generations. The sex ratio in different periods had no significant difference. Furthermore, there was no significant difference in wingless rate in different rearing time periods. Accordingly, the parasitoid’s fitness was affected by number of generations in both conditions. Although, mass rearing under laboratory condition provided wasps with more desired traits than those reared in insectary, both decreased fitness of T. brassicae when number of generations increased.

Keywords:

Angoumois grain moth , long-term rearing , parasitoid fitness , Sitotroga cerealella