Potential host use by the Mediterranean pine engraver (Orthotomicus erosus) in North America

The Mediterranean pine engraver, Orthotomicus erosus Wollaston, is an exotic bark beetle first detected in North America in 2004. Populations are currently confined to California, but their potential impacts on eastern North American conifers are uncertain. We assayed the attractiveness of several tree species under quarantine conditions. In a sequential no-choice olfactometer experiment, beetles were presented with a clean airstream and then air containing volatiles from red pine, white spruce, tamarack, eastern hemlock, balsam fir, or paper birch. A beetle that moved further in the odor-laden airstream than in the clean airstream was considered attracted. The percentage of tested beetles (n=240 per species) that were attracted was compared among tree species and with 50%-attraction, expected from random movement. Approximately 60% of all beetles tested were attracted to tree volatiles, regardless of the species, except for balsam fir, where the response did not differ from 50%. Beetles were attracted to volatiles from hosts and non-hosts. The ecological significance of these results is demonstrated through Monte Carlo simulation of the combined effects of long-range attraction, short-range acceptability, and developmental suitability of different tree species.