Plant Odor Analysis of Apple:  Antennal Response of Codling Moth Females to Apple Volatiles during Phenological Development

Volatile compounds were collected from apple branches (Malus domestica) at different developmental stages, and the antennal response of codling moth females (Cydia pomonella) to these compounds was recorded by electroantennography coupled to gas chromatography. Presence of a range of terpenoid compounds, many of which had antennal activity, was characteristic for volatile collections from branches with leaves, and from small green apples. Nine compounds from branches with leaves and green fruit consistently elicited an antennal response: methyl salicylate, (E)-β-farnesene, β-caryophyllene, 4,8-dimethyl-1,3(E),7-nonatriene, (Z)3-hexenol, (Z,E)-α-farnesene, linalool, germacrene D, and (E,E)-α-farnesene. The bouquet emitted from flowering branches contained in addition several benzenoid compounds which were not found after bloom. Small green apples, which are the main target of codling moth oviposition during the first seasonal flight period, released very few esters. In comparison, fully grown apples released a large number of esters, but fewer terpenoids. The study of apple volatiles eliciting an antennal response, together with a survey of the seasonal change in the release of these compounds, is the first step toward the identification of volatiles mediating host-finding and oviposition in codling moth females. Keywords: Host plant volatiles; phenology; headspace collection; electroantennography; apple; Malus domestica; codling moth; Cydia pomonella; Tortricidae; Lepidoptera