Electrophysiological and behavioural responses of Tomicus piniperda and Tomicus minor (Coleoptera : Scolytidae) to non-host leaf and bark volatiles

Leaf and bark volatiles from non-host birches, Betula pendula Roth. and Bet ula pubescens Ehrh, (Betulaceae), and aspen, Populus tremula L. (Salicaceae ), were tested on spring-dispersing Tomicus piniperda (L.) and Tomicus mino r (Hart.) by gas chromatographic - electroantennographic detection (GC-EAD) and by attractant-baited traps in southern Sweden. GC-EAD analysis of the head-space volatiles from fresh bark chips of B. pendula revealed two green leaf alcohols, 1-hexanol and (Z)-3-hexen-1-ol, that consistently elicited antennal responses by T. piniperda and T. minor. Further analyses with synt hetic mixtures showed that the antennae of these two Tomicus species also r esponded to other green leaf alcohols, such as (E)-2-hexen-1-ol found from the non-host leaves, and C-8-alcohols, 3-octanol and 1-octen-3-ol, from bar k: of non-host bitches and aspen. No antennal responses of the Tomicus spec ies were observed to green leaf C-6-aldehydes and C-6-acetate or to non-hos t bark volatiles like trans-conophthorin, benzaldehyde, salicylaldehyde, an d benzyl alcohol. In field trapping experiments, blends of electrophysiolog ically active green leaf alcohols or C-8-alcohols resulted in reductions (> 60%) in the number of T. piniperda captured compared with that for the kair omone-baited trap. When these two blends were combined, trap catch was furt her reduced (90%), which was not significantly different from that for the blank control. Neither the blend of two green leaf aldehydes plus the aceta te nor the bark compounds trans-conophthorin or benzyl alcohol reduced trap catches, Tomicus minor had a response pattern similar to that of T. pinipe rda. Hylurgops palliatus (Gyll.) (Coleoptera: Scolytidae) was attracted to the combination of kairomone and verbenone but not to kairomone and was not affected by the blends of green leaf volatiles. Our results suggest that s elected leaf-bath C-6-alcohols and the bark C-8-alcohols may have potential in developing semiochemical-based management programs against both pine sh oot beetles by repelling them from suitable breeding and feeding sites.