Mountain Pine Beetle

Insect Pest

Critical Threat

Affects: Lodgepole pine (primary), ponderosa pine, limber pine, whitebark pine

Photo: W.C. Guy / (CC-BY-3.0-US (Bugwood))

Identification & Biology

Native bark beetle whose populations have exploded due to drought and warmer winters that no longer kill overwintering larvae. Beetles mass-attack trees, introducing blue-stain fungi that stop water transport. Trees turn red and die within a year.

Current Status

Has killed billions of trees across western North America. Ongoing in all mountain states.

States affected:

Colorado Idaho Montana Utah Wyoming

What Homeowners Should Do

Preventive bark spray (carbaryl, bifenthrin) on high-value pines annually. Thin overcrowded stands to reduce stress. Water trees deeply during drought. Remove infested trees before spring beetle emergence.