Abstract
The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) utilizes a multi-component aggregation pheromone to mediate mass-attacks and thereby colonize otherwise unsusceptible trees. Females produce the attractant frontalin and a synergist, trans-verbenol. We investigated trans-verbenol to determine whether enantiomeric composition, airborne concentration, and possibly other factors might affect its biological activity. Newly-emerged females from Mississippi populations produced 54–87% of the (−)-enantiomer; females initiating galleries in logs produced lower amounts and a wider range of enantiomeric ratios [12–92% (−)]. Coupled gas chromatography-electroantennographic detection (GC-EAD) studies did not suggest large differences in the concentration threshold of olfaction for the two enantiomers. We examined the effect of adding trans-verbenol to traps located outside infested areas and baited with components of the aggregation attractant. Male attraction was similarly increased by lures with 3, 81, or 98% of the (−)-enantiomer of trans-verbenol, whereas females preferred 81 over 3%. When release rate of 81% (−)-trans-verbenol in traps was varied across three orders of magnitude (0.3, 3, and 30 mg/d), the data suggested a positive dose–response trend. A high release (i.e., 2–5 g/d) device of host odor alpha-pinene had a much stronger enhancing effect on trap catches than a trans-verbenol device (~30 mg/d), and trans-verbenol did not further enhance attraction when alpha-pinene was present. Our results suggest that the weak attraction-enhancing activity of trans-verbenol reported previously cannot be improved by adjusting the enantiomeric composition or release rate of lures, and furthermore there are no anticipated benefits of adding trans-verbenol to the D. frontalis monitoring lure.
Keywords
Dendroctonus frontalis, lure, bark beetle, enantiomer, dose–response
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Shepherd, William P., and Brian T. Sullivan. 2019. “Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae) Pheromone Component Trans-Verbenol: Enantiomeric Specificity and Potential as a Lure Adjuvant.” Environmental Entomology 48 (1): 193–201. https://doi.org/10.1093/ee/nvy169.