Can chemical cues from blossom buds influence cultivar preference in the apple blossom weevil (Anthonomus pomorum)?

The post-hibernating adults of the apple blossom weevil, Anthonomus pomorum (L.), show preferences for certain cultivars in mixed apple tree orchards. The degree of infestation of various cultivars was positively correlated w ith the density of flower buds at a comparable phenological stage, but the numbers of collected beetles were not linearly proportional to the bud dens ity of different cultivars. Hence other possible factors, namely chemical o nes, were investigated. Chromatographic analysis of apple tree bud emanatio ns showed that volatiles from two different apple cultivars that show a dif ferent attractiveness to the beetles, differed in chemical composition. Sev eral less volatile components of the bud emanation bouquet elicited antenno graphic responses in both male and female antennae. Four terpene hydrocarbo ns, namely 3-carene, perillene, caryophyllene and (E,E)-alpha-farnesene, we re identified among the components that produced distinct electrophysiologi cal responses in the antennae. These findings support a hypothesis that the adult weevils use chemical cues for olfactory discrimination during host-s earching behaviour.