Assessing the attractiveness of volatile plant compounds to western flowerthrips Frankliniella occidentalis

The responses of walking adult female western flower thrips. Frankliniella occidentalis, to plant volatiles at several concentrations were investigate d in a Y-shaped glass tube olfactometer. The simple experimental design all owed comparing the effect of numerous volatiles and differentiated clearly between attractive and repellent compounds. Western flower thrips were attr acted by the benzenoids benzaldehyde and p- and o-anisaldehyde; the monoter penes geraniol, nerol, linalool, and (+)-citronellol: the sesquiterpene (E) -beta -farnesene, eugenol, and 3-phenylpropionaldehyde; two phenylpropanoid s: and the nonfloral odor ethyl nicotinate. p-Anisaldehyde, nerol. ethyl ni cotinate, and (E)-beta -farnesene elicited positive responses at several co ncentrations: all other volatiles were attractive at a specific concentrati on. Salicylaldehyde, a benzenoid, elicited negative responses at two concen trations. Experimental series with several other volatiles belonging to the above mentioned chemical groups and the essential oils from rose and geran ium did not result in either clearly positive or negative responses by test ed thrips.