Volatiles Involved in the Nonhost Rejection of Fraxinus pennsylvanica by Lymantria dispar Larvae

Volatiles from green ash foliage or ambient air was trapped by Super Q and their chemical identities determined by GC−MS analysis. Effects of the whole mixture and individual chemical components of green ash volatiles on gypsy moth larval (GML) locomotory behavior were assayed in a T-tube arena. Green ash volatiles (treatment) proved significantly repellent to GML as compared to Super Q trappings of volatiles from the ambient air (control). Such observed effects were due to the combined repellencies of linalool, methyl salicylate, and farnesenes; however, the relatively major component, trans-ocimene, proved to be nonrepellent. The significance of such volatiles in GML orientation and host/nonhost decision is discussed. Keywords: Gypsy moth; green ash; repellency; volatiles; chemical identification