Stink bugs piling up on a windowsill or clustering near a ceiling light every fall isn't a sign of a dirty house. It usually means they're hunting for somewhere protected to spend the winter, and your walls look better to them than the yard does. This guide covers how to keep stink bugs out of your house in fall by sealing the specific gaps they use to get in, plus a no-mess way to remove the ones that already made it past the door.
A common species behind this pattern is the brown marmorated stink bug, usually shortened to BMSB. Unlike other stink bugs, it commonly overwinters in large groups inside sheltered places such as buildings, which is why homes tend to see more of them once the weather cools.
Spraying isn't the best fix. UC IPM identifies sealing gaps around doors, windows, screens, utility pipes, window air conditioners, vents, siding, and fascia boards as the best way to keep BMSB out. Outdoor insecticides around entry points may work temporarily but break down quickly, while indoor sprays aren't recommended.
Why do stink bugs come into houses in the fall?
BMSB isn't hunting for crumbs or moisture the way many household pests are. It's an invasive species native to East Asia that was accidentally introduced into the US. It has spread quickly in part by hitchhiking in vehicles and moved furniture and, as of 2021, had reached 47 US states and four Canadian provinces, according to UC Agriculture and Natural Resources.
Not every shield-shaped bug on the porch is this invader. California alone hosts more than 50 stink bug species, and the rough stink bug preys on caterpillars and other insect larvae and is considered beneficial. There's no need to identify or eliminate every stink bug spotted outdoors just because BMSB can enter homes.
BMSB congregates around buildings in late summer and early fall before moving into protected spaces to overwinter. Once inside, the bugs don't reproduce or damage the structure, according to UC IPM. Cleaning alone therefore won't close off the entry points. That's why the fix below focuses on the house envelope, not the housekeeping routine.
Where do stink bugs get into your house?
Before sealing anything, walk the house and find out where bugs could be getting in. UC IPM points to cracks around windows, doors, screens, utility pipes, window air conditioners, vents, siding, and underneath fascia boards.
Once a stink bug gets past the exterior, it can hide in gaps under or behind baseboards, around window and door trim, and near ceiling exhaust fans or light fixtures. UC IPM says BMSB also prefers high, cool locations, so upper areas deserve attention too.
Run through this checklist before starting repairs:
Exterior doors: check for gaps under sweeps and around the frame
Window screens: look for tears, holes, or gaps where the screen meets the frame
Window AC units: check the side panels and seal around the unit's perimeter
Utility penetrations: look for gaps where pipes and cables pass through exterior walls
Vents and fascia: inspect for openings that could admit insects without blocking the ventilation those openings are designed to provide
How to seal cracks to keep stink bugs out, step by step
What you'll need: appropriate caulk or sealant, a caulking gun if required, weatherstripping, a door sweep or threshold if needed, screen repair materials, a flashlight, and any other materials specified for the surface being repaired.
Exclusion is the best long-term approach. UC IPM recommends silicone, silicone-latex caulk, or foam sealant for appropriate exterior gaps, along with repaired screens, weatherstripping, tight-fitting door sweeps or thresholds, and properly sealed window AC units.
Inspect windows and doors. Look for visible openings around frames, damaged seals, and areas where insects could enter.
Seal appropriate exterior cracks. Use a sealant suitable for the gap and building material, following the product's directions.
Add or replace weatherstripping. UC IPM recommends weatherstripping around doorframe edges. Choose a product sized for the actual gap so the door can still close and latch normally.
Install or adjust door sweeps and thresholds. Exterior doors should have a tight fit along the bottom without preventing normal operation.
Repair or replace damaged screens. Also inspect window AC units, since gaps around them are a documented BMSB entry point. UC IPM recommends filling gaps around the unit and using screen material where necessary.
Address utility and vent openings carefully. Seal appropriate gaps around pipes and other penetrations, but don't block a functional vent, flue, drain, electrical component, HVAC opening, or gas connection. UC IPM specifically recommends screening the inside of gable vents to prevent attic entry while maintaining their function.
Stink bugs are also attracted to lights. UC IPM recommends turning off unnecessary lights and avoiding bright interior or exterior lights near an entrance when opening a door.
After finishing, inspect the repaired areas again for openings that could still admit insects. Don't use a lack of airflow as the goal around intentional ventilation openings. If a suspected entry point is high, inaccessible, or involves electrical, gas, HVAC, roofing, or another building system you're not qualified to alter, call an appropriate professional instead.
How to get rid of stink bugs in the house without crushing them
Stink bugs can release their characteristic odor when disturbed or crushed, so smashing one indoors can create a bigger nuisance than the bug itself.
UC IPM recommends a simple light trap for BMSB already inside. Fill a foil roasting pan or similar basin with some water and a few drops of dish soap. Place it in a dark room and point a light directly into the pan. The stink bugs are attracted to the light, fall into the soapy water, and drown.
That light is an important part of the trap. A basin of soapy water simply placed beneath a windowsill or ceiling fixture isn't the method UC IPM tested and recommends.
A vacuum is another option, although captured stink bugs can leave the vacuum smelling unpleasant. UC IPM suggests using a dedicated vacuum or placing a nylon stocking inside the vacuum tube and securing its end outside the tube so the bugs collect in the stocking instead of reaching the bag or canister.
Individual bugs can also be brushed into a container holding soapy water.
Skip indoor insecticide sprays. UC IPM says they're generally ineffective and doesn't recommend them for BMSB inside homes.
Troubleshooting: when sealing doesn't go as planned
If a door sweep still leaves a gap after installation, check the sweep and threshold against the manufacturer's adjustment and sizing instructions. An uneven or damaged threshold may require repair rather than simply adding a larger sweep.
If a window or door won't close smoothly after adding weatherstripping, don't force it shut. Check that the product is the correct size and installed in the location its manufacturer specifies.
A screen with a small repairable tear may be patchable, while badly damaged screens should be replaced. UC IPM specifically recommends repairing or replacing damaged window and door screens as part of BMSB exclusion.
For a window AC unit, seal gaps around the edges without interfering with drainage, airflow, electrical connections, or other parts required for safe operation. If the unit can't be fitted securely according to its installation instructions, correct the installation or get professional help rather than filling every opening with more sealant.
Yard cleanup isn't a substitute for structural exclusion. UC IPM's home-management guidance puts the emphasis on preventing BMSB from entering the structure in the first place.
Finish-line guidance
After sealing, inspect each door, window, screen, window AC unit, utility penetration, and other potential entry point again. If bugs keep showing up indoors in large numbers, don't reach for an indoor insecticide spray; extension guidance doesn't recommend it for this pest.
Recheck for missed openings first. Penn State Extension similarly identifies mechanical exclusion as the best way to keep BMSB from entering buildings and recommends sealing cracks around windows, doors, siding, utility pipes, chimneys, fascia, and other openings.
If an entry point is inaccessible or involves a vent, wiring, gas line, roofing, HVAC equipment, or structural repair, call the appropriate pest-control or building professional rather than modifying it yourself.
There's no need to eliminate every stink bug outdoors to solve an indoor BMSB problem. Focus on the building itself: repair the screens, close the gaps, improve door and window seals, and deal with the bugs that make it inside without crushing them. That's where the evidence for preventing an autumn invasion is strongest.
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