Comparisons of efficiency of two formulations of verbenone (4, 6, 6-trimethylbicyclo [3.1.1] hept-3-e3n-2-one) for protecting whitebark pine (Pinus albicaulis) from mountain pine beetle (Dendroctonus ponderosae)

Authors: PROGAR, ROBERT - Forest Service (FS); FETTIG, CHRISTOPHER - Forest Service (FS); MUNSON, STEVEN - Forest Service (FS); MORTENSON, LEIF - Forest Service (FS); SNYDER, CYNTHIA - Forest Service (FS); KEGLEY, SANDRA - Forest Service (FS); CLUCK, DANIEL - Forest Service (FS); STEED, BRYTTEN - Forest Service (FS); MAFRA-NETO, AGENOR - Isca Technologies, Inc; Rinella, Matthew - Matt

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 1/9/2021
Citation: Progar, R.A., Fettig, C.J., Munson, S.A., Mortenson, L.A., Snyder, C.L., Kegley, S.J., Cluck, D.R., Steed, B.E., Mafra-Neto, A., Rinella, M.J. 2021. Comparisons of efficiency of two formulations of verbenone (4, 6, 6-trimethylbicyclo [3.1.1] hept-3-e3n-2-one) for protecting whitebark pine (Pinus albicaulis) from mountain pine beetle (Dendroctonus ponderosae). Journal of Economic Entomology. 114(1):209–214. https://doi.org/10.1093/jee/toaa289.
DOI: https://doi.org/10.1093/jee/toaa289

Interpretive Summary: Whitebark pine is a North American tree that supplies food and habitat for wildlife. Mountain pine beetle is threatening whitebark pine throughout much of its range. Verbenone is a pheromone produced by pine beetle during feeding, and high concentrations of verbenone in air deter pine beetle from colonizing trees already supporting large numbers of the insect. Synthetic verbenone has been included in products that are applied to individual trees or forest stands to prevent pine beetle colonization. The most-used older product is a polyethylene pouch containing a verbenone-wetted pad that is stapled to trees. A more recently developed product is SPLAT® Verb (ISCA Technologies Inc. Riverside, CA), a verbenone impregnated viscous wax mixture that is applied with a caulking gun. Previous studies found SPLAT® Verb and polyethylene pouches similarly protected both individuals and small stands of lodgepole pine. In this study, we compared the ability of the two products to protect individual trees and small stands of whitebark pine. In Oregon, pouches and SPLAT® Verb performed similarly on medium and small trees, but large trees had greater survival when treated with SPLAT® Verb (~93%) than pouches (~82%). Compared to verbenone pouches, SPLAT® Verb appears to better protect whitebark pine from pine beetle. Other advantages of SPLAT® Verb over pouches is it is less visually obtrusive, slightly less expensive and does not need to be retrieved from the field because it biodegrades over time.

Technical Abstract: Whitebark pine, Pinus albicaulis Engelm., is a subalpine tree endemic to western North America. This species provides multiple ecosystem services and is suffering widespread mortality from mountain pine beetle, Dendroctonus ponderosae Hopkins. Verbenone is a pheromone produced as D. ponderosae feed, and high air concentrations of verbenone deter D. ponderosae from colonizing trees. Synthetic verbenone has been formulated into products used to prevent D. ponderosae from colonizing trees. We compared the ability of verbenone pouches and SPLAT Verb® to protect individuals and small stands of P. albicaulis. With individual trees in Montana, all treated trees survived regardless of verbenone formulation and rate, whereas untreated trees suffered 70 and 90% mortality in 2015 and 2016. In plot experiments in California and Oregon from 2015 to 2018, verbenone was applied to trees spaced ~10 m apart, and survival of small (12.7–23 cm DBH=diameter at 1.37-m height), medium (23.1–33 cm DBH) and large (>33 cm DBH) trees was compared. In California, where >80% of untreated trees survived, pouches increased survival ~2 to 3% and SPLAT® Verb increased survival ~4 to 7% regardless of tree size. In Oregon, verbenone pouches and SPLAT® Verb performed similarly on medium and small trees, but large trees had greater survival when treated with SPLAT® Verb (~93%) than pouches (~82%). Compared to verbenone pouches, SPLAT® Verb appears to better protect P. albicaulis from D. ponderosae.