Pheromone components in the larch bark beetle, Ips cembrae, from China:: Quantitative variation among attack phases and individuals

Ips cembrae adults were collected from larch log piles in northeast China, separated into six attack phases, and immediately frozen in liquid nitrogen. Three previously described aggregation pheromone components [ipsenol, ipsdienol, and 3-methyl-3-buten-1-ol (331-MB)] and six other volatiles of beetle origin (2-phenylethanol, geraniol, ipsenone, ipsdienone, myrtenol and verbenone) were identified and quantified by GC-MS from excised male hindguts. No amitinol, a recently reported aggregation pheromone component, was detected in our samples. The amounts of these volatiles (except the last two) showed a similar pattern of variation between attack phases in males. The largest amounts of most male volatiles were present in phases 1-2, when the nuptial chamber was being constructed or only one female was accepted. The amounts of the volatiles declined sharply in the following phases. The hindgut volatiles, mainly the pheromone components, from 46 individual males in phase 1 were also quantified. Ipsenol, ipsdienol, and 331-MB showed a large Variation in both amounts and proportions. The chirality of these two dominant aggregation pheromone components was determined as 100% (-)-enantiomer of ipsenol and 96% (+) enantiomer of ipsdienol. No male aggregation pheromone components were detected from mated females, except three extracts that were probably contaminated by male tissues.