Field Response of Black Turpentine Beetle to Pine Resin Oxidation and Pheromone Displacement

The black turpentine beetle, Dendroctonus terebrans, is an economically important pest of pines in the Southeastern U.S., with a high potential for invasion to other pine-rich regions. Dendroctonus terebrans attraction to an injured host tree lessens over time as the host material degrades. Likewise, kairomonal volatiles emitted from the host change as constituents of the defensive resin oxidize. Therefore we hypothesized that volatiles associated with a fresh host would be more attractive to D. terebrans than those associated with a dead or dying host. We replicated the natural oxidation process of turpentine, fractionated the distilled products to isolate the oxidized products, and deployed the complex mixtures to measure field attraction based on the amount of oxidation performed. Contrasting with previous studies, our results suggest that D. terebrans attraction is not primarily based on host tree degradation. In a second experiment incorporating Dendroctonus pheromones, we demonstrate D. terebrans has a displacement-dependent response to endo-brevicomin, a pheromone associated with the sympatric southern pine beetle, D. frontalis. This has implications not only for possible interspecific signaling, but also for the role of endo-brevicomin in D. terebrans colonization behavior. The results from this study broaden the understanding of D. terebrans chemical ecology and directly contribute to the development of an effective lure-based monitoring system that will benefit future research and management efforts. This may become important if the species is established outside its native range, as in the closely related red turpentine beetle, Dendroctonus valens, which caused mass pine tree mortality following its introduction to Asia.