Text Size 
Western Pine Beetle
Host: Ponderosa pine.
 |
| Western pine beetle galleries |
| L. Livingston |
Distribution: Throughout range of ponderosa pine.
Identification: White-orange masses of pitch (resin mixed with wood particles) on main bole; reddish-brown boring dust in bark crevices; distinctive, circuitous galleries apparent under bark layer; crown fading within one year of attack; woodpeckers flaking bark off main bole.
Damage: Beetles feed in phloem and introduce blue-staining fungi which, in combination, girdle the tree.
Ecology: Western pine beetle preferentially attack weakened, old, and stressed trees but can also reach outbreak levels in apparently healthy stands.
Life cycle: Two generations may be produced each year, with adults attacking trees primarily between June and September. Larvae feed in distinct circuitous that cross over each other. Beetles may overwinter as eggs, larvae, or adults.
Management
Silvicultural manipulations: Western pine beetle preferentially attack suppressed trees. 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. Western pine beetle also attack old, decadent trees so diversifying age classes and including tree species that do not host western pine beetle (such as western larch) will also minimize stand-level tree mortality.
 |
| Woodpecker feeding on western pine beetle |
| K. Gibson |
 |
| Adult western pine beetle |
| Forestry Images |
Brood trees: Identifying and removing trees currently infested with western pine beetle offspring can directly reduce populations in the stand. Accurate identificaton 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 conditins. 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.
Chemical treatments: Protective chemicals are available to spray on the main bole of the tree that effectively deter western pine beetle infestation. Please contact the DNRC Forest Pest Management Program coordinator or a certified forest pesticide applicator to discuss this option.
Pheromones: Note: verbenone is NOT effective against western pine beetle.
Links |
||||
| 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) |
|
