Termites in Oregon: Dampwood and Subterranean
Oregon's termites come in two kinds, and they need opposite responses. One lives in wet, rotting wood and mostly tells you about a moisture problem. The other lives in the soil and can eat sound framing. Here's how Oregon State University tells them apart and what each one means for your house.
The short version
Oregon's structural termites are the Pacific dampwood termite, which nests in wet, decaying wood and swarms in late summer or fall, and the western subterranean termite, which lives in soil, tunnels along foundations and may swarm any time of year. Drywood termites are uncommon in the Pacific Northwest. OSU says flying termites alone aren't cause for alarm, and professional help is the route for an infestation in the house.
Oregon at a glance
- Termite pressure
- Slight to moderate
- Termites to know
- Western subterranean, Pacific dampwood
- Why termites like it here
- Wet winters west of the Cascades and dry summers, with dampwood termites in wet wood and subterranean termites in soil.
- Who licenses pest control
-
Oregon Department of Agriculture, Pesticides Program
Check a company's license - Inspection report for home sales
- NPMA-33 Wood Destroying Insect Inspection Report
On this page
Two termites, two problems
Oregon State University Extension's Solve Pest Problems names the region's structural termites. The Pacific dampwood termite nests in moist, water-damaged wood; woodpiles are common nest sites. It's big: winged adults about an inch long including wings. The western subterranean termite lives in the soil and enters buildings through soil tunnels along foundations; its workers are about the size of a grain of rice.
The difference matters. Washington State University, describing the same Northwest species, says dampwood termites don't nest in dry, sound wood, so finding them usually means a moisture problem like wood touching soil. Subterranean termites commonly attack sound wood and can cause serious damage. A drywood termite exists in the region too, but OSU calls it uncommon, and OSU Extension's Kaci Buhl has written that Oregon doesn't have the drywood variety as an established problem.
When termites swarm in Oregon
OSU says dampwood termites swarm in late summer or fall, and subterranean termites may swarm at any time of year, often after a good rain.
| Termite | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Western subterranean Sunny days after the first fall rains | some swarms | some swarms | some swarms | some swarms | peak | common | ||||||
| Pacific dampwood Evenings, late summer and fall | some swarms | common | peak | common |
Dampwood or subterranean?
From OSU Extension's Solve Pest Problems and WSU's Pestsense.
| Feature | Dampwood | Subterranean |
|---|---|---|
| Lives in | Wet, rotting wood | Soil, tunneling into wood |
| Swarmers | About 1 inch, orange-brown | About 3/8 inch, black |
| Swarm season | Late summer or fall | Any time of year |
| Damage to sound wood | Rare | Common and serious |
| First fix | Remove the moisture and wet wood | Professional treatment |
See types of termites and termite damage vs water damage.
What to do in Oregon
For dampwood termites, the fix is mostly moisture. OSU's prevention list: remove firewood and wood debris, keep lumber away from buildings, fix leaks, eliminate damp areas and improve ventilation under buildings and in attics. WSU adds removing construction formwood from the soil and keeping a vapor barrier in a ventilated crawlspace, and says pesticides are rarely needed for dampwood termites. See crawlspace moisture and termites.
For subterranean termites, OSU recommends professional control: soil treatments at the foundation or bait stations, often 10 to 15 around a home's perimeter. OSU says home-use insecticides won't work unless moisture is removed and damaged wood repaired. Buhl notes that in Oregon, termite treatments are often done only at the pre-construction stage, so an existing house may never have been treated. A formal inspection by a trained professional is the next step.
Signs to look for
OSU's signs differ by termite. Subterranean termites leave soil tunnels on the inside and outside of foundations. Dampwood termites leave hollowed or damaged wood, usually in places that have been wet for a long time, such as a sill under a leaking window or a post sitting in soil. Drywood termites, uncommon here, leave small piles of droppings called frass. OSU also points out that termite activity outdoors, in stumps and logs well away from the house, is part of the natural environment and doesn't need treatment. More in signs of termites.
Inspections and licensing
The Oregon Department of Agriculture licenses pesticide applicators, and wood-destroying pest work falls under the Structural subcategory of its industrial, institutional, health and structural category. Oregon's Construction Contractors Board doesn't require home inspector certification for someone who only does pest, dry rot or wood-destroying organism inspections. In practice that means a termite inspector may not be a certified home inspector, so ask what license the inspector holds and what the report will cover. See WDI inspections.
For Oregon homeowners
Do
- Find and fix the moisture when you see dampwood termites
- Keep firewood and lumber off the ground and away from the house
- Get a professional inspection for soil tunnels on the foundation
- Ask the inspector what license they hold
Don't
- Panic over a fall flight of dampwood swarmers
- Spray store insecticide on rotten wood and call it fixed
- Leave construction formwood in the soil
- Assume an older house was ever treated
Questions people ask
What termites live in Oregon?
Mainly the Pacific dampwood termite and the western subterranean termite. A drywood termite occurs in the Pacific Northwest but OSU calls it uncommon.
When do termites swarm in Oregon?
Dampwood termites swarm in late summer or fall. Subterranean termites can swarm any time of year, often after a good rain.
Are dampwood termites a serious problem?
They're mostly a sign of moisture. They live in wet, decaying wood and rarely attack sound wood, so fixing the moisture and replacing wet wood is the main cure.
Who licenses termite applicators in Oregon?
The Oregon Department of Agriculture, under the structural subcategory for wood-destroying pests.
Keep reading
Sources
- Oregon State University Extension, Solve Pest Problems: Termites (updated 2025)
- Oregon State University Extension: How can I prevent a termite infestation? (Buhl, 2023)
- Washington State University Extension, Pestsense: Termites
- Oregon Department of Agriculture: Pesticide license categories
- Oregon Construction Contractors Board: Specialty licenses