Reduced plant nutrition under elevated CO(2) depresses the immunocompetence of cotton bollworm against its endoparasite

Estimating the immunocompetence of herbivore insects under elevated CO(2) is an important step in understanding the effects of elevated CO(2) on crop-herbivore-natural enemy interactions. Current study determined the effect of elevated CO(2) on the immune response of Helicoverpa armigera against its parasitoid Microplitis mediator. H. armigera were reared in growth chambers with ambient or elevated CO(2), and fed wheat grown in the concentration of CO(2) corresponding to their treatment levels. Our results showed that elevated CO(2) decreases the nutritional quality of wheat, and reduces the total hemocyte counts and impairs the capacity of hemocyte spreading of hemolymph of cotton bollworm larvae, fed wheat grown in the elevated CO(2,) against its parasitoid; however, this effect was insufficient to change the development and parasitism traits of M. mediator. Our results suggested that lower plant nutritional quality under elevated CO(2) could decrease the immune response of herbivorous insects against their parasitoid natural enemies.