Abstract: [Objective] The Asian larch bark beetle Ips subelongatus (Coleoptera: Scolytidae) is the main larchpest insect in northeastern China. Its continuous outbreaks in these regions pose a serious threat to the larch forests. In order to explore the mutual action mechanism of different allelochemicals from host, non-host, and sibling species as well as to provide a strong technical support in the biological control of I. subelongatus in large area, we investigated the effects of allelochemicals on aggregation behaviors of I. subelongatus.[Method] The behavioral bioassay methods were used to investigate the behavioral differences of I. subelongatus in responses to different enantiomers of its aggregation pheromone components, host volatiles, non-host volatiles, and pheromone components from sibling species.[Result] The aggregation pheromone components were determined to be S-(-)-ipsenol and S-(+)-ipsdienol enantiomeric compositions in field trapping bioassays, which presented very high aggregation activity. Electroantennogram dose-responses studies indicated that antennal response threshold to S-(-)-ipsenol and S-(+)-ipsdienol were all 0.1 μg and the saturation level were 100 μg. Furthermore, the behavioral effects of I. subelongatus to electroantennographic detection (EAD) active semiochemicals from hosts, non-hosts, and closely related bark beetle species were tested in the field trapping bioassays. The attraction of I. subelongatus to a synthetic pheromone source was significantly increased (1.45-1.65 times) when the EAD-active monoterpenes, S-(-)-β-pinene or 3-carene was added to the source. But, addition of EAD-active components S-α-pinene or Terpinolene to trap with synthetic pheromone did not significantly increase trap catches. In field trapping experiments, the non-host volatile (Z)-3-hexen-1-ol reduced I. subelongatus trap catches by 71%, showing a strong inhibitory effects on the pheromone source. Linalool demonstrated the same inhibitory effects as (Z)-3-hexen-1-ol. The other non-host volatiles, for example, Myrtenol, (E)-3-hexen-1-ol, (E)-2-hexen-1-ol, 1-hexanol, 3-octanol, and 1-octen-3-ol had no synergistic or antagonistic effects on I. subelongatus attraction when added to the pheromone trap, whereas cis-verbenol (the major constituent of the aggregaton pheromone of Ips typographus) and trans-verbenol inhibited its attraction to the S-(-)-ipsenol and S-(+)-ipsdienol-containing attractive blend. However, adding the verbenone to pheromone-baited traps did not reduce I. subelongatus attraction, which had an inhibitory effect on I. typographus pheormone baited traps.[Conclusion] EAD-active host and non-host volatiles either had synergized or antagonized, or no effect on I. subelongatus response to its aggregation pheromone; the strong inhibitory effects of semiochemicals from sibling species on I. subelongatus response to its aggregaton pheormone were observed. These results laid the foundation for the development of efficient lures and biological control of I. subelongatus in large area.

Key words: Ips subelongatus, sibling species, allelochemicals, aggregation pheromone, host volatiles, non-host volatiles, field trapping bioassay