ARS | Publication request: Bark beetles, Pityogenes bidentatus, responding to aggregation pheromone avoid conifer monoterpene odors when flying but not when walking

Submitted to: Psyche
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 2012
Publication Date: May 25, 2012
Citation: Byers, J.A. 2012. Bark beetles, Pityogenes bidentatus, responding to aggregation pheromone avoid conifer monoterpene odors when flying but not when walking. Psyche. 2012:1-10.

Interpretive Summary: Bark beetles are serious pests of conifer forests and plantations that provide lumber and paper resources. Aggregation pheromones are used to monitor population levels of bark beetles and also to mass trap them for control. The bark beetle Pityogenes bidentatus is known to avoid non-host Norway spruce (Picea abies) and healthy host Scotch pine (Pinus sylvestris) while flying to aggregation pheromone (grandisol and cis-verbenol). This behavior of avoiding monoterpenes appears to aid beetles in finding hosts, which are branches of damaged, broken, or unhealthy Scotch pine. In contrast, beetles walking in the laboratory bioassay do not avoid monoterpene vapors at release rates over several orders of magnitude in combination with aggregation pheromone. The bark beetle may benefit from avoiding monoterpenes when flying by avoiding landing in harmful resinous areas and more efficiently find appropriate host bark unable to produce defensive resin. The beetle is likely to avoid resin when walking by using their senses of vision and touch, but would still enter entrance holes with higher concentrations of monoterpene vapor to find mates and food. Understanding differences in behavioral responses to aggregation pheromone when walking or flying may help in refining monitoring and control methods for other bark beetle pest species.

Technical Abstract: Previous studies have provided evidence that monoterpene odors from healthy host Scotch pine (Pinus sylvestris) and non-host Norway spruce (Picea abies) significantly reduce the attraction of flying bark beetles, Pityogenes bidentatus, to their aggregation pheromone components (grandisol and cis-verbenol) in the field. This behavior of avoiding monoterpenes appears to aid beetles in finding hosts, which are branches of damaged, broken, or unhealthy Scotch pine. In contrast, beetles walking in the laboratory open-arena olfactometer do not avoid monoterpene vapors at different release rates over several orders of magnitude in combination with aggregation pheromone. The bark beetle may benefit from avoiding monoterpenes when flying to efficiently avoid nonhosts and harmful resinous areas of hosts, thereby increasing its ability to find appropriate host bark unable to produce defensive resin. The beetle is likely to avoid resin when walking by using visual and thigmotactic senses, but would still enter entrance holes with higher concentrations of monoterpene vapor in order to reproduce.