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18 February 2022 The Role of Wind and Semiochemicals in Mediating Switching Behavior in the Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae)
Brian T. Sullivan, Cavell Brownie
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Abstract

Aggressive bark beetles colonize and kill healthy conifers through pheromone-mediated mass aggregation. In several species, the focal point of aggregation moves progressively from mass-attacked ‘focus trees’ to adjacent, unattacked ‘recipient trees’, resulting in infestation growth. This process, termed ‘switching’, is hypothesized to be mediated in whole or in part by antiaggregation pheromones released by beetles as colonization intensifies on a focus tree. We tested this hypothesis with the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), by using a windvane apparatus that maintained an unbaited, black, cylindrical trap (surrogate for a recipient tree) continuously 4 m downwind from an identical trap baited with synthetic aggregation attractant (surrogate for a focus tree). In two of three replicated trials, addition of pheromone components with antiaggregation activity, endo-brevicomin or verbenone, to the upwind trap caused a significant but small (<15%) increase in the proportion of beetles caught in the downwind trap. In one of two trials with endo-brevicomin, this shift was associated with a significant reduction in catches in the downwind trap and an overall reduction in catches of beetles by the trap pair. This suggests that an inhibitor-induced increase in landings on the recipient relative to the focus tree may be countered by the radial effects of the inhibitor, which at sufficiently high release may reduce responses to both the focus and recipient tree. We discuss spatial factors that might govern the role of antiaggregation pheromones in stimulating infestation growth as well as additional factors that likely govern switching behavior.

Published by Oxford University Press on behalf of Entomological Society of America 2022. This work is written by (a) US Government employee(s) and is in the public domain in the US.
Brian T. Sullivan and Cavell Brownie "The Role of Wind and Semiochemicals in Mediating Switching Behavior in the Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae)," Environmental Entomology 51(2), 340-350, (18 February 2022). https://doi.org/10.1093/ee/nvac006
Received: 15 November 2021; Accepted: 13 January 2022; Published: 18 February 2022
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KEYWORDS
anemotaxis
antiaggregation
bark beetle
host selection
pheromone
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