Analysis of volatiles induced by oviposition of elm leaf beetle Xanthogaleruca luteola on Ulmus minor

Egg deposition of the elm leaf beetle Xanthogaleruca luteola causes the emi ssion of volatiles from its food plant, Ulmus minor. These volatiles are ex ploited by the egg parasitoid, Oomyzus gallerucae, to locate its host. In c ontrast to other tritrophic systems, the release of volatiles is not induce d by feeding but by egg deposition. Previous investigations showed that the release is systemic and can be triggered by jasmonic acid. Comparison of h eadspace analysis revealed similarities in the blend of volatiles emitted f ollowing egg deposition and feeding. The mixture consists of more than 40 c ompounds; most of the substances are terpenoids. Leaves next to those carry ing eggs emit fewer compounds. When treated with jasmonic acid, leaves emit a blend that consists almost exclusively of terpenoids. Dichloromethane ex tracts of leaves treated with jasmonic acid were also investigated. After s eparation of extracts of jasmonate induced elm leaves on silica, we obtaine d a fraction of terpenoid hydrocarbons that was attractive to the parasitoi ds. This indicates that jasmonic acid stimulates the production of terpenoi d hydrocarbons that convey information of egg deposition to the parasitoid.