Stink Bugs on Your House in Fall: Why They're Here and What to Do

By the YardClues editorial team · Updated

Shield-shaped brown bugs crowding your siding, window frames, and doors in late September and October are most likely brown marmorated stink bugs looking for a warm place to spend the winter. They don't bite, aren't poisonous to people, and don't damage the house, but they do stink when crushed or disturbed. The fix is to seal the gaps they use to get inside, and to vacuum or drop any indoor bugs into soapy water rather than squashing them.

Most likely causes

  • Brown marmorated stink bugs — 5/8-inch mottled brown shields with white-banded antennae
  • Western conifer seed bugs — longer, narrower, with flattened leaf-like hind legs
  • Native brown stink bugs — similar shield shape but plain antennae with no white bands
  • Bugs already inside the walls — stragglers that wake up on warm days and wander to windows

Not quite what you're seeing? Answer four quick questions and the clue finder will point you to a closer match.

Compare the possible causes

Possible cause Key signs When it happens How likely
Brown marmorated stink bugs gathering to overwinter Dozens of 5/8-inch, shield-shaped, mottled brownish-gray bugs on sunny south- and west-facing walls, window frames, and doors; white bands on the antennae and a light-and-dark checkered edge along the sides of the abdomen Late September through October, especially on warm, sunny afternoons Very common
Stink bugs already inside the house Slow, clumsy bugs on windows, lamps, and ceilings, often buzzing loudly when they fly; a sharp, cilantro-like smell if one is bumped or crushed Warm winter days and early spring, sometimes on sunny late-fall days Very common
Western conifer seed bugs A brown bug that's noticeably longer and narrower than a stink bug, with flattened, leaf-like expansions on the hind legs; also gives off an odor when handled Fall, often in homes near pine or other conifer trees Common
Native brown stink bugs Shield-shaped brown bugs similar in size, but the antennae are plain with no white bands Summer in gardens; occasionally on walls in fall Less common
Garden stink bugs and squash bugs Bugs clustered on tomatoes, peppers, corn, fruit, or squash vines, with cloudy, corky, or dimpled spots on the produce Mid to late summer, before the fall move toward the house Common

Visual clues to check

  • Check the antennae: white bands near the tips point to the brown marmorated stink bug
  • Look at the edge of the abdomen from above for alternating light and dark bands
  • Check the shape: a broad, 5/8-inch shield is a stink bug; a longer, narrower body suggests a western conifer seed bug
  • Look at the hind legs — flattened, leaf-like sections mean a western conifer seed bug, not a stink bug
  • Note which walls they favor: sunny south and west sides, window frames, and door trim are classic stink bug gathering spots
  • Gently nudge one with a tissue (don't squeeze) — a sharp, cilantro-like odor confirms a stink bug or seed bug
  • Inspect the sunny side of the house for gaps around window frames, siding seams, utility lines, vents, and window AC units

The causes in detail

Brown marmorated stink bugs gathering to overwinter

This invasive bug from Asia spends the summer feeding on fruit, vegetables, and ornamental plants, then shifts to shelter-seeking as days shorten. They land on the warmest walls of the house and probe for cracks around windows, siding, utility lines, window AC units, and attic vents. Once inside a wall void or attic they go dormant for the winter. Your house isn't infested in the usual sense — it's simply a convenient hotel.

Stink bugs already inside the house

The bugs you find indoors in winter almost always moved into the walls or attic back in fall. A warm spell or a sunny window wakes some of them, and they crawl out toward the light, often trying to get back outdoors. They don't breed indoors, don't eat anything in the house, and don't chew wood or fabric, so the number you see won't multiply over the winter.

Western conifer seed bugs

This native bug is frequently mistaken for a stink bug because it invades homes at the same time and also smells when disturbed. Check the hind legs: the flattened, leaf-shaped section is the giveaway. It's equally harmless to people and the house, and the same sealing and vacuuming steps work for both.

Native brown stink bugs

Several native stink bugs look a lot like the invasive species. They live mostly outdoors on plants and are far less likely to gather on a house in large groups. If the antennae lack white bands and you only see a few, you're probably looking at a native species.

Garden stink bugs and squash bugs

Outdoors, stink bugs are a garden and orchard pest that pierce fruit and vegetables and leave discolored, pithy spots under the skin. Squash bugs, a different garden insect, are often confused with them but stay on squash and pumpkin plants. A big garden population in summer often means more bugs knocking on your siding come fall.

When to worry

  • Hundreds of bugs pouring onto the house every sunny afternoon — a heavy year where professional exterior treatment may be worth it
  • A steady stream of bugs indoors in winter, which suggests a large gap into the attic or wall voids that still needs sealing
  • Bugs swarming garden tomatoes, peppers, fruit trees, or corn in late summer, damaging the harvest
  • Bugs you can't identify that are biting, or that are found in beds — stink bugs don't bite, so look for another culprit

What to do now

  1. Seal cracks and gaps with caulk around window frames, door trim, siding seams, and where pipes, cables, and dryer vents enter the house — ideally before mid-September, but sealing now still stops the next wave
  2. Repair torn window screens, add weatherstripping and door sweeps, and screen attic and soffit vents
  3. Remove window AC units in early fall, or seal tightly around them if they must stay in
  4. Vacuum indoor bugs with a bagged or dedicated vacuum; a knee-high stocking pushed into the hose and secured with a rubber band catches them so you can tie it off and toss it
  5. Knock bugs off windows and walls into a jar of soapy water — they drown quickly, which is the simplest way to kill them
  6. Set a pan of soapy water under a lamp at night in a dark room to catch some of the wanderers
  7. For very heavy infestations year after year, have a licensed pest professional treat the exterior in late summer before they move in

What not to do

  • Don't crush stink bugs indoors — that releases the odor right where you're standing
  • Don't spray insecticides or set off bug bombs inside; it doesn't stop new bugs, and dead bugs in wall voids can attract carpet beetles
  • Don't use your main household vacuum without a bag or stocking — the smell can linger in the canister and hose
  • Don't count on dryer sheets, essential oils, or other home 'repellents' — there's little evidence they work, and sealing gaps does
  • Don't seal attic or soffit vents shut; screen them instead so the house can still breathe

Frequently asked questions

Do stink bugs actually stink?

Yes, but only when they're threatened. When disturbed or crushed, a stink bug releases a pungent odor that many people compare to cilantro. Left alone, they don't give off much smell at all, which is why vacuuming or the soapy-water jar beats squashing them.

Why are there stink bugs in my house?

They moved in during fall to spend the winter somewhere sheltered. Stink bugs slip through small gaps around windows, siding, utility lines, AC units, and vents, then go dormant in walls and attics. Warm winter days and early spring wake them up, which is why they suddenly show up at windows and lights.

Are stink bugs poisonous or dangerous?

No. Stink bugs don't bite people, aren't poisonous to people, and don't damage your home or furniture. A dog or cat that eats one may drool or gag because of the terrible taste, but the bugs are a nuisance rather than a hazard.

How do I keep stink bugs out of my house, and what deters them?

Exclusion is what really works: caulk cracks around windows and siding, repair screens, weatherstrip doors, screen attic and soffit vents, and remove window AC units in fall. Popular deterrents like dryer sheets and essential oils have little evidence behind them. The best time to seal is before mid-September, but closing gaps in October still keeps more bugs out.

What kills stink bugs instantly?

A jar or bucket of soapy water is the simplest answer. Knock the bug in and the soap breaks the surface tension so it sinks and drowns within moments. It's cheaper and safer than spraying anything indoors, and it avoids the smell that crushing causes.

How do I get rid of stink bugs outside?

Outdoors, focus on keeping them off the house rather than wiping them out. Seal entry points on the sunny walls, knock clusters into soapy water, and pick bugs off garden crops in late summer. For severe yearly invasions, a licensed pest professional can treat the exterior before the bugs move in.

Related yard clues

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Still not sure? Compare with these clues

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