Clusters on sunny walls
Groups of bugs on south- and west-facing siding on warm fall afternoons.
Spiders, Wasps & Seasonal
Boxelder & Stink Bug Control in Seattle
Every fall, boxelder bugs and stink bugs look for a warm place to spend the winter, and your walls are it. They do not bite or breed indoors, but they gather by the hundreds on sunny siding and slip into wall voids and attics. We seal the gaps they use, treat the surfaces they gather on at the right time, and clear the ones already inside.
Call (206) 944-0849 All treatments
- Fall timing
- Siding and window sealing
- Wall void treatment
- Answered 24/7
Reviewed by Marjorie Tidwell, Pest Prevention Writer. Updated 2026-10-05.
In short: Call (206) 944-0849 when you see clusters of red-and-black boxelder bugs or brown shield-shaped stink bugs on south- and west-facing walls, or finding them indoors near windows. The best results come from sealing entry gaps and treating gathering surfaces in late summer and early fall, before they move inside; bugs already in wall voids are treated and removed.
What this treatment covers
Seal and treat before they move in
Boxelder bugs are black with red markings and feed mostly on boxelder and maple seeds. Stink bugs, including the brown marmorated stink bug that has been spreading in Washington, are brown and shield-shaped and release an odor when disturbed. Both are overwintering pests: in late summer and fall they gather on warm, sunny walls and then crawl into gaps around windows, siding, soffits and vents to spend winter inside wall voids and attics.
They do not breed indoors and do not damage the structure, but on warm winter days they wake up and wander into living spaces, especially near windows. Squashing stink bugs releases their smell, and vacuuming them can leave odor in the vacuum.
Control is all about timing and sealing. In late summer and early fall we seal gaps around windows, siding, utility penetrations and vents on the sunny sides of the house, and treat the exterior surfaces where bugs gather. Bugs already inside wall voids can be treated, and stragglers are removed with a dedicated vacuum.
What the visit includes
- Inspection of sunny walls, windows, siding and roofline gaps
- Sealing of entry points on gathering sides
- Timed exterior treatment of gathering surfaces
- Wall void and attic treatment where bugs are already inside
- Advice on boxelder and maple trees near the house
- Follow-up in fall if pressure is heavy
Catch it early
Six signs of overwintering bugs
Red-and-black bugs near maples
Boxelder bugs gathering on or under boxelder and maple trees.
Shield-shaped brown bugs indoors
Stink bugs appearing at windows in winter and spring.
A musty smell when disturbed
Stink bugs release an odor when crushed or vacuumed.
Bugs in the attic
Accumulations in attic corners or around gable vents.
Bugs around window frames
Gaps in window trim and siding are the main entry points.
The Seattle angle
Fall in Seattle brings them to the walls
Seattle's late-summer sun warms south- and west-facing siding, and that warmth is what draws overwintering insects to the walls in September and October. Boxelder and maple trees are common in yards and street plantings, which supports boxelder bug populations, and the brown marmorated stink bug has been increasing in parts of Washington.
Older homes with settled siding, aging window trim and original vents give these insects plenty of gaps. Sealing those gaps also helps with cluster flies, spiders and other fall invaders that use the same routes.
How the job runs
How the job runs
Call in late summer
Earlier is better; sealing before bugs move in prevents most indoor sightings.
Inspect the sunny sides
Gaps around windows, siding, vents and utility lines are mapped.
Seal entry points
Gaps sealed with appropriate sealants and screens.
Treat gathering surfaces
Exterior treatment timed to when bugs gather on walls.
Clear the stragglers
Wall void treatment and removal for bugs already inside.
Honest numbers
What boxelder and stink bug control costs
Pricing follows the sealing work and the size of the exterior surfaces involved. What sets the number:
- Number of windows and gaps to seal on the gathering sides
- Siding type and condition
- Roofline and gable vent access
- Exterior footage treated
- Whether bugs are already in wall voids or the attic
- Follow-up visits in heavy years
A written quote covers sealing and treatment. Many owners pair this with fall spider and occasional invader work, since the same gaps serve all of them.
Make the visit count
Before the visit
- Note which walls the bugs gather on and at what time of day
- Photograph a few bugs for identification
- Avoid crushing stink bugs indoors
- Use a dedicated vacuum or bag for indoor bugs
- Check window screens and trim for gaps
- Note boxelder or maple trees near the house
Straight answers
Boxelder and stink bug questions
No. They are a nuisance, not a health risk, and they do not damage the house.
No. They overwinter indoors and leave in spring to feed and breed outside.
They use the same warm walls and gaps. Sealing those gaps is the long-term fix.
Not necessarily. Sealing and timed treatment usually control the problem without removing trees.
No. We can treat wall voids and remove bugs, then seal before next fall.
Late summer or early fall, before they move into the walls.
Often booked together
Related treatments
Bugs piling up on the sunny wall? Seal before they move in.
Call (206) 944-0849
Talk to a technician
Keep them out of the walls this winter
Gaps sealed, gathering surfaces treated at the right time, and stragglers cleared. Call in late summer for the best results.
Call (206) 944-0849Answered 24/7 from our Seattle service office.