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Colonization of hosts by bark beetles is generally mediated by aggregation pheromones. Species competing for the same resource can limit interspecific interactions and maintain reproductive isolation by using different pheromones. In the southern United States, 3 sympatric species of Ipsbreed in pine hosts, each with a different pheromone blend. Ips avulsus(Eichhoff) uses ipsdienol and lanierone; Ips calligraphus(Germar) uses ipsdienol, cis-verbenol, and trans-verbenol; and Ips grandicollis(Eichhoff) uses ipsenol. Different species can also minimize cross-attraction by using different enantiomeric ratios of the same pheromones. Studies on the enantiomeric ratio of ipsdienol used by I. avulsushave come to contradictory conclusions in part because of geographic and seasonal variation. There is growing evidence that semiochemical context, in the form of different co-baits used in trapping experiments, may also play a role in the responses of I. avulsusto enantiomeric ratios of ipsdienol. We conducted a trapping study at 2 locations with traps baited with (+)-ipsdienol or racemic ipsdienol and co-baited with ipsenol, lanierone, or both ipsenol and lanierone. We found context-dependent effects of both lanierone and ipsenol on the response of I. avulsusto ipsdienol. We suggest that responses to different bait and co-bait combinations may have been shaped by different types of interactions such as the absence of conspecifics or a related species, or the presence of beneficial or antagonistic interspecific interactions.

AbstractIn 2012, we evaluated the effects of hardwood cerambycid pheromones (syn-2,3-hexanediol, 3-hydroxyhexan-2-one, and 3-hydroxyoctan-2-one) on catches of bark and woodboring beetles in ethanol-baited multiple-funnel traps in two field trials in Oregon and Washington, United States of America. Catches of Phymatodes aeneusLeConte (Coleoptera: Cerambycidae) in ethanol-baited traps increased with the addition of 3-hydroxyhexan-2-one lures or the 3,2-hydroxyketone lure blend (3-hydroxyhexan-2-one + 3-hydroxyoctan-2-one). Catches of the predator Thanasimus undatulus(Say) (Coleoptera: Cleridae) in ethanol-baited traps increased with the addition of 3-hydroxyhexan-2-one lures but not syn-2,3-hexanediol lures or 3-hydroxyoctan-2-one lures. The 3,2-hydroxyketone lure blend decreased catches of the corthyline ambrosia beetle, Gnathotrichus sulcatus(LeConte) (Coleoptera: Curculionidae), but not the xyleborine ambrosia beetle, Xyleborinus saxesenii(Ratzeburg), (Coleoptera: Curculionidae). Catches of Ptilinus basalisLeConte (Coleoptera: Anobiidae) in ethanol-baited traps increased with the addition of the 3,2-hydroxyketone lure blend.