Volatiles emitted by different cotton varieties damaged by feeding beet armyworm larvae

Volatile compounds elicited by insect herbivore feeding damage in five cotton cultivars and one naturalized cotton variety were examined by allowing beet armyworm larvae to feed overnight on leaves and collecting volatiles from the plants in situ. Of 23 compounds identified from larval damaged leaves, terpenes and lipoxygenase-hydroperoxide lyase-derived volatiles predominated. No pronounced differences in the levels of volatile emission were noted from leaves of undamaged plants of the different varieties. However, average volatile emission from damaged leaves of the naturalized variety was almost sevenfold higher than from damaged leaves of the commercial cultivars. This was despite the fact that larvae preferred feeding on the leaves of commercial cultivars over those of the naturalized variety in choice tests.