Antennal responses of four species of tree-killing bark beetles (Coleoptera: Scolytidae) to volatiles collected from beetles, and their host and nonhost conifers

Abstract

Host selection in tree-killing bark beetles (Coleoptera: Scolytidae) is mediated by a complex of semiochemical cues. Using gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses, we conducted a comparative study of the electrophysiological responses of four species of tree-killing bark beetles, the Douglas-fir beetle, Dendroctonus pseudotsugae, Hopkins, the mountain pine beetle, D. ponderosae Hopkins, the spruce beetle, D. rufipennis Kirby, and the western balsam bark beetle, Dryocoetes confusus Swaine, to volatiles captured by aeration of 1) bole and foliage of four sympatric species of conifers, Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, lodgepole pine, Pinus contorta var. latifolia Engelm., interior spruce, Picea engelmannii x glauca, and interior fir, Abies lasiocarpa x bifolia, and 2) con-and heterospecific beetles at three stages of attack. We identified 13 monoterpenes in the conifers and nine compounds in the volatiles of beetles that elicited antennal responses. There was no qualitative difference in the terpene constitution of the four species of conifers and very little difference across beetle species in their antennal response to compounds from conifers or beetles. The lack of species-specific major or minor components in conifers suggests that beetles would need to detect differences in the ratios of different compounds in conifers to discriminate among them. Attraction to hosts and avoidance of nonhost conifers may be accentuated by perception of compounds emitted by con-and heterospecific beetles, respectively. The 22 compounds identified are candidate semiochemicals with potential behavioural roles in host location and discrimination.

Effect of Water Stress and Fungal Inoculation on Monoterpene Emission from an Historical and a New Pine Host of the Mountain Pine Beetle

“…All volatile monoterpenes emitted by lodgepole and jack pine seedlings in the study can be detected by the MPB (Huber et al, 2000;Pureswaran et al, 2004b). Some of these host monoterpenes synergize MPB response to the aggregation pheromones trans-verbenol and exo-brevicomin in trapping studies (Borden et al, 2008).…”

“…In some areas, MPB attack is linked to pines infested with A. mellea (Tkacz and Schmitz, 1986). Mountain pine beetle antennae do not respond to bornyl acetate (Pureswaran et al, 2004b), but it is possible that it can taste this compound since olfactory and gustatory information are processed in different areas of the insect brain (DeBruyne and Warr, 2006). Gustatory assessment could be way for MPB to evaluate the health status of a host tree and to determine how well defended it is.…”

Host Defense Mechanisms against Bark Beetle Attack Differ between Ponderosa and Lodgepole Pines

“…Although we did not focus on myrcene and terpinolene in particular at the outset of this investigation, these monoterpenes can be attractive or elicit antennal responses in the mountain pine beetle [37,38,42]. We found differences in terpinolene between the two host species.…”

“…However, β-phellandrene has been shown to cause a positive flight response in the mountain pine beetle when coupled with an aggregation pheromone blend, though it did not significantly increase trap catches across a multitude of release rates [36]. Since this compound elicits attraction of Ips pini, and antennal responses in the mountain pine beetle [37,38], further investigation may be warranted to determine the importance of β-phellandrene to lodgepole pines relative to bark beetle defense.…”

The Effect of Water Limitation on Volatile Emission, Tree Defense Response, and Brood Success of Dendroctonus ponderosae in Two Pine Hosts, Lodgepole, and Jack Pine

“…High amounts of bornyl acetate in jack pine needles has been previously reported (Pauly and von Rudloff, 1971;Lapp and von Rudloff, 1982). Bornyl acetate might not be biologically important for MPB, since its antennae do not respond to it (Pureswaran et al, 2004b). The low amount of α-pinene in jack pine needles compared to phloem suggests that foliar chemistry alone is likely not a good predictor of chemically mediated interactions between bark beetles and their host trees.…”