Leaf and bark volatiles from non-host angiosperm trees were tested on the conifer bark beetle, Ips duplicatus by gas chromatographic-electroantennographic detection (GC-EAD) and by pheromone-baited traps in Sweden and Inner Mongolia, China, respectively. GC-EAD analysis of the headspace volatiles from fresh bark chips of Betula pubescens revealed trans-conophthorin, two green leaf volatiles (GLVs): 1-hexanol and (Z)-3-hexen-1- ol, and two C8-alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal responses by I. duplicatus. The identification of these antennally-active compounds was confirmed in further GC-EAD recodrings with synthetic mixtures. Antennal responses were also found to synthetic (E)-2-hexen-1-ol, that has been identifed from the leaves of non-host birch and aspen species. In field trapping experiments, blends of antennally active, GLV alcohols or C8-alcohols, or trans-conophthorin alone resulted in significant reductions (27-60%) in the number of I. duplicatus captured compared with the pheromone-baited trap. The unsuitable host compound, verbenone, also siginificantly reduced the trap catches up to 60% in both experiments. The strongest disruptive effect resulted from the addition of the combination of GLV-alcohols, C8-alcohols and Vn to the pheromone trap, which caused 84% of trap catch reduction. The blend of two GLV aldehydes plus the acetate increased the trap catches in 1998 and had no negative or positive effects in 1999. Our results suggest that these nonhost leaf and bark volatiles are important olfactory signals used by I. duplicatus in descriminating between host and nonhost species. They may have great significance in developing semiochemical-based management program against the outbreaks of I. duplicatus by reducing attacks on suitable hosts and thereby decreasing population levels and damage.

Index terms: Ips duplicatus, host selection, nonhost volatiles, NHVs, Green leaf volatiles, GLVs.