Pest profile

Mountain Pine Beetle

Dendroctonus ponderosae · Coleoptera: Curculionidae[3]

Mountain pine beetle is a native bark beetle of western North America whose outbreaks can kill millions of pines.[1]

Mountain pine beetle, a small black cylindrical bark beetle, on a pale pitch tube of resin on a pine trunk
Mountain pine beetle, a small black cylindrical bark beetle, on a pale pitch tube of resin on a pine trunk. (c) Justin Paulin, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Popcorn-shaped masses of resin called pitch tubes, brown, pink or white, form on the trunk where beetles bore in.[1]
  • Boring dust collects in bark crevices and at the tree base, and the crown turns yellow to red about 8 to 10 months after a successful attack.[1]
  • Under the bark you'll find vertical egg galleries and blue-gray stained sapwood.[1]

Look-alikes

Look-alikeHow to tell them apart
Ips (engraver) beetlesIps have a sharply spined rear end; Dendroctonus beetles such as mountain pine beetle have a gently curved one.[1]
Red turpentine beetleA relative that attacks injured pines, mostly the lower trunk and root collar.[1][2]

Where it lives

It's native to western North America; in California it attacks lodgepole and sugar pines, especially at high elevations.[1][2]

US map: public records from 10 states since 1990 (GBIF).

Biology and life cycle

Adults leave dead trees in late summer and mass-attack large living pines; each pair lays about 75 eggs in a vertical gallery.[1]

Larvae overwinter under the bark using glycerol as antifreeze; there's one generation a year in Colorado.[1]

Beetles carry bluestain fungi that help kill the tree.[1]

Damage and signs

  • Hosts include ponderosa, lodgepole, Scotch and limber pine; once a tree is infested, nothing practical can save it.[1]
  • In an outbreak, beetles from one infested tree can kill two or more trees the next year.[1]

Health risk

It attacks pines; CSU Extension mentions no risk to people.[1]

Control

Prevention

Thinning crowded stands to well-spaced, healthy trees is the long-term remedy; stressed trees are attacked first.[1]

Sanitation

Peel, burn, chip or bury infested logs before beetles emerge in summer, and don't bring infested firewood near pines.[1]

When to call a professional

Preventive bark sprays applied in early summer can protect high-value green trees for one beetle flight; a licensed applicator can help.[1]

Common questions

What are the popcorn-like resin blobs on my pine trunk?
They're pitch tubes, a classic sign of mountain pine beetle attack.[1]
Can I save a pine that mountain pine beetles have already attacked?
No; CSU Extension says nothing practical can save an infested tree.[1]

Sources

  1. Colorado State University Extension, “Mountain Pine Beetle (Fact Sheet 5.528).” extension.colostate.edu/resource/mountain-pine-beetle/ (accessed 2026-10-06)
  2. University of California Statewide IPM Program, “Bark Beetles (Pest Notes).” ipm.ucanr.edu/home-and-landscape/bark-beetles/ (accessed 2026-10-06)
  3. iNaturalist, “Dendroctonus ponderosae taxon page (order and family).” www.inaturalist.org/taxa/53543 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.