Lygus hesperus FEEDING AND SALIVARY GLAND EXTRACTS INDUCE VOLATILE EMISSIONS IN PLANTS1

Induction of plant volatiles by leaf-chewing caterpillars is well documented. However, there is much less information about volatile induction by insects with different feeding habits. We studied the induction of plant volatiles by a piercing–sucking insect, the western tarnished plant bug Lygus hesperus Knight. Adults of both genders and nymphs of Lygus induced the local emission of a blend of volatiles from both cotton and maize. Feeding by Lygus also induced the systemic emission of volatiles that was similar but less complex than the blend emitted at the site of feeding. Infestation by mated, mature adult females (>4 days old), but not by nymphs or mature males, caused detectable emission of α-pinene, myrcene, and (E)-β-caryophyllene, compounds that are stored in the glands of cotton tissue. This indicated that damage to glands in the petiole and leaf by the female ovipositor, rather than feeding, contributed significantly to the emission of these volatiles. Girdling the plant stem to disrupt phloem transport markedly decreased the movement of 14C-labeled photosynthetic products to the apex of the plant, and this treatment also markedly reduced the amount of systemically induced volatiles caused by Lygus feeding. Lygus salivary gland extracts were capable of inducing emission of the same volatile blend as measured for plants infested by feeding insects or treated with volicitin, an elicitor isolated from caterpillar regurgitant. The results indicate that ∗ To whom correspondence should be addressed. E-mail: [email protected] 1Mention of a trade name does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval over other products that may also be suitable. 5Current address: Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2 Canada.