Douglas-fir Beetle

How to identify it

• Look for reddish-brown boring dust collecting in bark crevices and for pitch streamers on the trunk, usually most plentiful midway up the tree; attacks often don't start until 11 to 15 feet above the ground.^[3]
• Under the bark, eggs are laid in niches alternating on opposite sides of the egg gallery, with larval galleries etched into the inner bark on both sides, a distinctive pattern.^[2]
• On trees killed earlier, pouch fungi may grow out of the beetle exit holes.^[3]

Where it lives

Native to western North America and found throughout the range of Douglas-fir, including all of Oregon, Washington and Idaho.^[2][3][1]

US map: public records from 8 states since 1990 (GBIF). View the map

Biology and life cycle

There is one generation a year, and most tree deaths come from the spring flight.^[1][3]

Larvae feeding in the phloem girdle the tree, and once a tree is infested it can't be saved.^[1]

Populations usually build in freshly downed trees for one or two years after a blowdown or fire and then attack standing trees; without new fresh material they subside to normal levels by about the fourth year.^[3][1]

Damage and signs

• It prefers large Douglas-firs, generally more than 12 to 14 inches in diameter, and can also infest windthrown western larch that is still green.^[3][1]
• Trees stressed by root disease, fire injury, drought or defoliation are less able to fight off attacks with resin.^[1]

Health risk

It attacks trees only; none of the sources reports any harm to people or pets.^[1]

Control

Prevention

Pouches of MCH, a naturally occurring beetle repellent, stapled to trees in spring before the beetle flight have proven very effective at protecting high-value trees.^[1]

Thinning crowded, older Douglas-fir stands reduces their susceptibility.^[1]

Sanitation

Remove or process windthrown, damaged and beetle-infested Douglas-firs before the next spring flight, since the beetle is strongly attracted to downed trees with green inner bark.^[1]

Related profiles

• Western Pine Beetle
• Mountain Pine Beetle
• Spruce Beetle
• Douglas-fir Tussock Moth
• Bark beetles in pines and firs

Common questions

Why are Douglas-firs dying near me a year or two after a windstorm?

Douglas-fir beetles breed in trees blown down by wind and then attack nearby standing trees in the following one or two years.^[3][1]

How can I protect my Douglas-firs?

Clean up windthrown and infested trees before the spring beetle flight, and put MCH repellent pouches on valuable trees before the beetles fly.^[1]

Sources

1. Idaho Department of Lands, “Douglas-fir Beetle (Forest Pest Fact Sheet, 2020).” www.idl.idaho.gov/wp-content/uploads/sites/2/2020/03/2016-single-pest-fact-sheet-Douglas-fir-Beetle_3_19_2020.pdf (accessed 2026-10-17)
2. USDA Forest Service, “Douglas-fir Beetle (Forest Insect & Disease Leaflet 5, rev. February 2014; M. M. Furniss and S. J. Kegley; copy hosted by Montana DNRC).” dnrc.mt.gov/_docs/forestry/Forestry_Assistance/Forest_Pests/Douglas-firBeetle-FIDL.pdf (accessed 2026-10-17)
3. USDA Forest Service (DecAID), “Douglas-Fir Beetle (DecAID Advisor species account).” apps.fs.usda.gov/decaid/views/douglas_fir_beetle.html (accessed 2026-10-17)
4. iNaturalist, “Dendroctonus pseudotsugae taxon page (order and family).” www.inaturalist.org/taxa/48905 (accessed 2026-10-06)