Electrophysiological and behavioral responses of Dendroctonus frontalis (Coleoptera: Curculionidae) to volatiles isolated from conspecifics.

Olfactory sensitivity of the southern pine beetle, Dendroctonus frontalis Zimmermann, to compounds isolated from the mid/hindguts of newly emerged conspecific adults was assayed with coupled gas chromatography-electroantennographic detection. All previously reported pheromones for D. frontalis plus eight additional compounds (fenchyl alcohol, myrtenal, cis-verbenol, trans-pinocarveol, acetophenone, trans-myrtanol, cis-myrtanol, and 2-phenylethanol) consistently elicited antennal responses from at least one sex. The eight additional compounds were assayed individually at three release rates (0.4-0.8, 3-9, and 25-100 mg/d) for the ability to alter D. frontalis responses to traps baited with D. frontalis attractant (4 mg/d frontalin and 17 mg/d alpha-pinene). At the high release rate, cis-verbenol enhanced attraction of D. frontalis females, whereas the other seven compounds significantly reduced attraction of one or both sexes. Acetophenone significantly reduced attraction of male D. frontalis at the low release rate, and five compounds (fenchyl alcohol, trans-pinocarveol, acetophenone, cis-myrtanol, and 2-phenylethanol) reduced attraction of one or both sexes at the intermediate rate. Only acetophenone significantly altered the sex ratio of beetles trapped, decreasing the proportion of males. Attraction of predatory checkered beetles (Cleridae) was enhanced by cis-verbenol released at the high rate but was not altered by any compound inhibitory to D. frontalis. Analyses of volatiles from individual D. frontalis indicated that the majority of the eight compounds were produced in greater quantities by newly emerged beetles than ones attacking pine bolts. Five of the compounds were associated predominantly with one sex. Possible ecological roles of these compounds in the biology of D. frontalis are discussed.