Mountain Pine Beetles Use Volatile Cues to Locate Host Limber Pine and Avoid Non-Host Great Basin Bristlecone Pine.
The tree-killing mountain pine beetle (Dendroctonus ponderosae Hopkins) is an important disturbance agent of western North American forests and recent outbreaks have affected tens of millions of hectares of trees. Most western North American pines (Pinus spp.) are hosts and are successfully attacked by mountain pine beetles whereas a handful of pine species are not suitable hosts and are rarely attacked. How pioneering females locate host trees is not well understood, with prevailing theory involving random landings and/or visual cues. Here we show that female mountain pine beetles orient toward volatile organic compounds (VOCs) from host limber pine (Pinus flexilis James) and away from VOCs of non-host Great Basin bristlecone pine (Pinus longaeva Bailey) in a Y-tube olfactometer. When presented with VOCs of both trees, females overwhelmingly choose limber pine over Great Basin bristlecone pine. Analysis of VOCs collected from co-occurring limber and Great Basin bristlecone pine trees revealed only a few quantitative differences. Noticeable differences included the monoterpenes 3-carene and D-limonene which were produced in greater amounts by host limber pine. We found no evidence that 3-carene is important for beetles when selecting trees, it was not attractive alone and its addition to Great Basin bristlecone pine VOCs did not alter female selection. However, addition of D-limonene to Great Basin bristlecone pine VOCs disrupted the ability of beetles to distinguish between tree species. When presented alone, D-limonene did not affect behavior, suggesting that the response is mediated by multiple compounds. A better understanding of host selection by mountain pine beetles could improve strategies for managing this important forest insect. Moreover, elucidating how Great Basin bristlecone pine escapes attack by mountain pine beetles could provide insight into mechanisms underlying the incredible longevity of this tree species.
Department of Wildland Resources, Utah State University, 5230 Old Main Hill, Logan, UT, 84322, United States of America.
Curtis A
CA
Gray
USDA Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, Bozeman, Montana, United States of America.
Justin B
JB
Runyon
Department of Wildland Resources, Utah State University, 5230 Old Main Hill, Logan, UT, 84322, United States of America.
Michael J
MJ
Jenkins
Department of Wildland Resources, Utah State University, 5230 Old Main Hill, Logan, UT, 84322, United States of America.
Andrew D
AD
Giunta
D000818:Animals; D000081008:Bicyclic Monoterpenes; D001517:Coleoptera / Q000502:physiology*; D003463:Cues; D053138:Cyclohexenes / Q000378:metabolism*; D005260:Female; D060434:Herbivory; D000077222:Limonene; D008297:Male; D039821:Monoterpenes / Q000378:metabolism*; D028223:Pinus / Q000502:physiology*; D012903:Smell; D013729:Terpenes / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000378:metabolism*
D000081008:Bicyclic Monoterpenes; D053138:Cyclohexenes; D039821:Monoterpenes; D013729:Terpenes; D055549:Volatile Organic Compounds; D000077222:Limonene; C030218:3-carene