Volatile emissions triggered by multiple herbivore damage: beet armyworm and whitefly feeding on cotton plants

Abstract—Plants are commonly attacked by more than one species of herbi-vore, potentially causing the induction of multiple, and possibly competing, plant defense systems. In the present paper, we determined the interaction be-tween feeding by the phloem feeder silverleaf whitefly (SWF), Bemisia tabaci Gennadius (B-biotype D B. argentifolii Bellows and Perring), and the leaf-chewing beet armyworm (BAW), Spodoptera exigua Hübner, with regard to the induction of volatile compounds from cotton plants. Compared to undam-aged control plants, infestation with SWF did not induce volatile emissions or affect the number and density of pigment glands that store volatile and non-volatile terpenoid compounds, whereas infestation by BAW strongly induced plant volatile emission. When challenged by the two insect herbivores simul-taneously, volatile emission was significantly less than for plants infested with only BAW. Our results suggest that tritrophic level interactions between cotton, BAW, and natural enemies of BAW, that are known to be mediated by plant volatile emissions, may be perturbed by simultaneous infestation by SWF. Pos