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25 November 2018 Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae) Pheromone Component trans-Verbenol: Enantiomeric Specificity and Potential as a Lure Adjuvant
William P. Shepherd, Brian T. Sullivan
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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.

Published by Oxford University Press on behalf of Entomological Society of America 2018. This work is written by (a) US Government employee(s) and is in the public domain in the US.
William P. Shepherd and Brian T. Sullivan "Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae) Pheromone Component trans-Verbenol: Enantiomeric Specificity and Potential as a Lure Adjuvant," Environmental Entomology 48(1), 193-201, (25 November 2018).
Received: 21 August 2018; Accepted: 26 October 2018; Published: 25 November 2018

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bark beetle
Dendroctonus frontalis
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