|Rodriguez-Saona, Cesar - UNIV OF TORONTO, CAN|
|Canas, Luis - UNIV OF AZ, MARICOPA|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2003
Publication Date: November 1, 2003
Citation: RODRIGUEZ-SAONA, C., CRAFTS-BRANDNER, S.J., CANAS, L.A. VOLATILE EMISSIONS TRIGGERED BY MULTIPLE HERBIVORE DAMAGE: BEET ARMYWORM AND WHITEFLY FEEDING ON COTTON PLANTS. JOURNAL OF CHEMICAL ECOLOGY. 2003. V. 29 2539-2550 Interpretive Summary: Natural enemies of leaf-chewing insect pests use odors emitted from damaged plants in prey/host location. However, it is likely that a given plant might be infested by multiple herbivores at the same time. In this paper we tested how the presence of the silverleaf whitefly impacted the feeding behavior of another cotton pest, the beet armyworm. There was a much lower level of volatile chemical release from cotton plants infested with both pests compared to those infested only with beet armyworm. Decreased consumption of leaf area by beet armyworm in the presence of whiteflies partially explained the result. It was concluded that the presence of multiple herbivores could perturb tritrophic interactions between crop plants, herbivores, and predators of herbivores that are dependent on chemical signals emitted by plants. This factor should be considered in developing biocontrol strategies for cotton pests. This work will be useful to scientists in the public and private sectors.
Technical Abstract: Plants are commonly attacked by more than one species of herbivore, potentially causing the induction of multiple, and possibly competing, plant defense systems. In the present paper, we determined the interaction between feeding by the phloem feeder silverleaf whitefly (SWF) Bemisia tabaci Gennadius (B-biotype = B. argentifolii Bellows & Perring) and the leaf chewing beet armyworm (BAW) Spodoptera exigua Hübner with regard to the induction of volatile compounds from cotton plants. Compared to undamaged 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 simultaneously, 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. Possible mechanisms by which the presence of whiteflies may attenuate volatile emissions from caterpillar-damaged cotton plants are discussed.