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Mountain Pine Beetle

Dendroctonus ponderosae

Mountain pine beetle mortality

Host: Native and introduced species of pine trees, including lodgepole, ponderosa, whitebark, limber, and white pines.

Distribution: Throughout range of pines with most notable outbreak currently in the Helena and Butte areas.

Pitch tubes on lodgepole pine

Identification: Reddish-orange masses of pitch (resin mixed with wood particle) on main bole; distinctive galleries apparent under bark layer with a "J" at the base; crown fading within one year of attack.

Blue stain in whitebark pine

Damage: Beetles feed in phloem and introduce blue-staining fungi which in combination, girdle the tree.

Ecology: Bark beetles must mass attack in order to overcome a tree's natural defense mechanisms. They communicate via chemical messages, called pheromones, and can recruit other beetles by emitting a specific aggregation pheromone. As the tree becomes too full to sustain offspring, they switch to an anti-aggregation pheromone, essentially sending a "no vacancy" message to other beetles.

Life Cycle: Adult beetles emerge from trees and fly between June and August, although weather and location may affect exact timing. Adults attack trees by boring under the bark and excavating a vertical gallery up to 30 inches long, laying eggs along the margins. Eggs hatch into larvae that feed on the phloem and disrupt the water and nutrient transport system of the tree. Larvae feed until cold winter temperatures initiate dormancy. Mountain pine beetles overwinter under the bark predominantly as larvae. Mountain pine beetle generally completes one generation per year in Montana although; at higher elevations they may require two years to reach maturity.

Mountain pine beetle pitch tube


Silvicultural manipulations: Pine trees respond to mountain pine beetle by “pitching out” with pressurized resin. Therefore, thinning stands to reduce competition for light, nutrients, and water will enhance the vigor of residual trees and consequently promote resilience to beetle activity. Diversifying age classes and including tree species that do not host mountain pine beetle (such as western larch) will also minimize stand-level tree mortality.

Mountain pine beetle galleries

Brood trees: Identifying and removing trees currently infested with mountain pine beetle offspring can directly reduce populations in the stand. Accurate identification is critical for this tactic to be successful. Infested trees will commonly have an apparently healthy, green crown. Closer inspection might reveal pitch tubes on the bole, although these diagnostic structures are not always evident, especially in dry conditions. Pealing back the bark will expose galleries. Look for larvae, pupae, or adults under the bark to determine current infestation. Brood trees must be removed from the stand as immature beetles can successfully continue development in a cut tree.

Mountain pine beetle galleries with distinctive "J" hook

Log decks: Mountain pine beetle will continue to develop in trees even after they are cut. Therefore, it is critical to remove infested logs from the site well before the next beetle flight period in order to inhibit dispersal.

Preventative Sprays : Protective chemicals are available to spray on the main bole of the tree that effectively deter mountain pine beetle infestation.

Verbenone on ponderosa pine

Pheromones: Mountain pine beetle must mass attack in order to overcome a tree’s natural defense mechanisms. They communicate via chemical messages, called pheromones, and can recruit other beetles by emitting a specific aggregation pheromone that solicits other beetles to attack the same tree. As the tree becomes too full to sustain additional offspring, they switch to an anti-aggregation pheromone, essentially sending a “no vacancy” message to other beetles. Researchers and manufacturers have successfully isolated the anti-aggregation chemical, verbenone, that acts as a naturally occurring repellent and can be used to treat small-scale acreages prone to mountain pine beetle activity. Additional information can be requested from the manufacturers of this product. As of January 2011, there are two companies distributing verbenone capsules to the United States:

Synergy Semiochemical Corp.
Box 50008, South Slope RPO
Burnaby, B. C. Canada V5J 5G3
Phone: 604-454-1122
Contech, Inc.
7572 Progress Way
Delta, B. C. Canada V4G 1E9
Phone: 604-940-9944

Verbenone can also be purchased from various retailers throughout the state. MT Pesticide Act and Administrative Rules of MT require that a person selling or charging to apply have a valid pesticide applicator/dealer license.  If you are interested in applying for an applicator or dealer license, please contact the Montana Department of Agriculture at 444-5400.  Homeowners and landowners applying verbenone on their own property do not need a license to purchase verbenone or apply it.


The DNRC Forest Pest Management Program does not distribute pheromones.


Forest Insect and Disease Leaflet (FIDL)   Field Guide - Identification   Management Guide

Additional Common Forest Insects in Montana

Douglas-fir Beetle Red Turpentine Beetle
Douglas-fir Tussock Moth
Spruce Beetle
Fir Engraver Western Pine Beetle
Mountain Pine Beetle Western Spruce Budworm
Engraver Beetles (Ips species)  


Dept. of Natural Resources & Conservation
1625 Eleventh Ave.
Helena, MT 59601
Phone: (406) 444-2074
Fax: (406) 444-2684