Effect of Bacillus thuringiensis on Trichogramma brassicae Life History Parameters on Cotton Bollworm Eggs

Integration of different pest control tactics into a larger program is a principle in modern IPM. Interaction between different tactics and possible antagonism between them then will become important. A popular integration is integration of egg parasitoids, Trichogramma spp. and larvicidal microbial agent, Bacillus thuringiensis Berliner against some field crop moth-pests, particularly in bollworm-cotton system. Although sequence of application allow avoiding direct antagonism, but indirect effects on the next generation of the parasitoid via treating the target pest’s larvae is not impossible. Some direct effect via overlapping of different stages of the pest is also possible. Therefore, studying possible maternal effects on parasitoids of the next generation that are developing on B.t.-treated host larvae is required. In this study, response of Trichogramma brassicae Bezdenko, was studied on two kinds of hosts; first bollworm, Helicoverpa armigera Hubner eggs laid by those females that treated by LC20 of B. thuringiensis in third instar. The second one control (untreated) individuals. Life history parameters were compared between the two groups by two-sided t-test. Fortunately no significant difference was observed between the two groups. It means that B.t. had no undesirable effect on T. brassicae. The mean value of R0, rm and T were 41.22 ± 3.85 female/female/generation, 0.3545 ± 0.009 /d and 10.49 ± 0.19 d as average of the two treatments. Thus, B. t. is safe for integration into Trichogramma application programs.