Olfactory responses of Dryocosmus kuriphilus Yasumatsu (Hymenoptera,Cynipidae) to host plant volatiles
Abstract: The chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera,Cynipidae), is a serious pests of Castanea spp. in many cultivation areas. Due to the lack of a sexpheromone system, studies have been initiated on the host plant-chestnut wasp interactions inorder to identify attractive volatile compounds potentially useful for developing monitoring andcontrol tools. In the present study electroantennographic (EAG) and behavioural experimentswere carried out in order to evaluate the olfactory response of the adult wasps to volatiles (n =14) previously identified from an attractive host odour source. All compounds tested elicitedmeasurable EAG responses. The most effective antennal stimulants were (E)-2-hexenal, (E)-2-hexenol, hexyl acetate, (E)-2-hexenyl acetate, and (E)-3-hexenol. Y-tube olfactometer bioassaysconfirmed that a blend of all identified compounds in the same ratio, as in the attractive hostodour material, is attractive to adult wasps compared to a solvent control. In subtractivebehavioural assays, removal of (E)-2-hexenal or aliphatic alcohols [hexanol, (Z)-3-hexenol, (E)-3-hexanol, (E)-2-hexenol] or (Z)-3-hexenyl hexanoate from the attractive complete blend did notresult in a significant loss of attractiveness. Results confirm the capability of the peripheralolfactory system of D. kuriphilus to selectively perceive host plant volatiles and suggest that aspecific ratio of ubiquitous volatiles is needed for attraction. Laboratory and field studiesexamining the behavioural responses of D. kuriphilus to various dosages of individual syntheticcompounds and their mixtures are in progress to find out those are crucial in host plant location.