Identification of a Potential Third Component of the Male-Produced Pheromone of Anoplophora glabripennis and its Effect on Behavior

The Asian longhorned beetle, Anoplophora glabripennis, is considered to be one of the most serious invasive pests of deciduous trees in North America. An efficient monitoring trap is needed to detect and delimit new introductions and assess population densities of established infestations. Previous studies on A. glabripennis have shown that males produce a two-component aggregation pheromone that consists of a 1:1 blend of 4-(n-heptyloxy)butan-1-ol and 4-(n-heptyloxy)butanal. Moderate attraction in field trapping studies suggested that there may be additional chemical cues missing. Volatiles from male A. glabripennis were examined to identify other potential pheromone components. Gas chromatographic / electroantennographic (GC/EAD) analyses of male aerations detected a consistent EAD-active response to a previously unidentified compound. This compound was identified as (3E,6E)-α-farnesene. Both male and female beetles were antennally responsive to this sesquiterpene, and both sexes were attracted to it in olfactometer bioassays at different doses. When (3E,6E)-α-farnesene was combined with 4-(n-heptyloxy)butan-1-ol and 4-(n-heptyloxy)butanal, attraction of both sexes increased compared to assays using 4-(n-heptyloxy)butan-1-ol and 4-(n-heptyloxy)butanal alone.