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How to identify it
- Under the bark, the adult beetles cut winding, criss-crossing galleries that look like spaghetti; in ponderosa pine, Idaho's forestry agency notes this pattern is unique to the western pine beetle.[1][2]
- Woodpeckers flaking off the outer bark to reach the larvae is a common sign of an attacked tree.[1][2]
- Attacked trees may push out pitch to repel the beetles; trees killed by the beetle fade like other beetle-killed pines.[2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Mountain pine beetle | Also attacks the main trunk of pines, but makes vertical egg galleries and attacks many pine species rather than just ponderosa pine.[1][3] |
| Pine engraver | Ips beetles usually attack the tops of trees and smaller material.[1] |
Where it lives
Found through most of the western states, and in Idaho wherever ponderosa pine grows.[1][2]
Biology and life cycle
It mainly overwinters as larvae under the bark and has two generations a year in Oregon.[2][1]
The beetles carry blue-stain fungi into the tree, and together the beetles and fungi girdle it by destroying the phloem, the inner bark tissue that moves water and sugars.[3]
Damage and signs
- It attacks ponderosa pines more than about 6 inches across, preferring large trees, and also attacks Coulter pine in California.[1][3]
- Outbreaks usually build in trees weakened by drought, fire, root disease, soil compaction or overcrowding, and during outbreaks it can kill even vigorous trees.[1][2]
Health risk
It attacks pine trees only; none of the sources reports any harm to people or pets.[1]
Control
Prevention
Thinning overcrowded ponderosa pine stands is the best way to prevent bark beetle problems; around homes, avoid soil compaction and root injury near mature pines.[1][2]
Sanitation
Identify and remove beetle-infested trees, finishing before the beetles emerge in March and April in Oregon, and handle firewood from infested pines carefully so beetles don't emerge near live trees.[1][2]
Pesticides
Preventive insecticides on high-value trees must be applied before the beetle flights.[1]
Common questions
- What are the winding tunnels under the bark of my dead ponderosa pine?
- Winding, criss-crossing galleries in the inner bark of a ponderosa pine are the signature of the western pine beetle.[1][2]
- How can I protect my ponderosa pines?
- Keep trees vigorous, thin crowded stands, avoid soil compaction around mature pines and remove infested trees promptly; preventive sprays must go on before the beetles fly.[1][2]
Sources
- Oregon Department of Forestry, “Western Pine Beetle (Forest Health Fact Sheet, March 2017).” egov.oregon.gov/odf/Documents/forestbenefits/Western%20Pine%20Beetle.pdf (accessed 2026-10-17)
- Idaho Department of Lands, “Western Pine Beetle (Forest Pest Fact Sheet, 2020).” web.archive.org/web/20201016171215/www.idl.idaho.gov/wp-content/uploads/sites/116/2020/07/Western_Pine_Beetle_fact_sheet_FINAL_3_20_2020.pdf (accessed 2026-10-17). Archived copy (Internet Archive, captured 2020-10-16); the original page https://www.idl.idaho.gov/wp-content/uploads/sites/116/2020/07/Western_Pine_Beetle_fact_sheet_FINAL_3_20_2020.pdf returns 404 (file removed).
- USDA Forest Service, “Western Pine Beetle (Forest Insect and Disease Leaflet 1).” www.fs.usda.gov/sites/default/files/users/user3914/FHP-files/FIDL-01-WesternPineBeetle.pdf (accessed 2026-10-17)
- iNaturalist, “Dendroctonus brevicomis taxon page (order and family).” www.inaturalist.org/taxa/218218 (accessed 2026-10-06)