For homeowners, stink bug season comes twice a year. In fall, usually September through October, brown marmorated stink bugs gather on sunny walls and squeeze into homes to spend the winter. In spring, roughly late April to mid-May, the ones that overwintered inside wake up and wander into living spaces trying to get back outdoors. On warm winter days you’ll see a few in between.
Stink bugs don’t bite, breed indoors or damage the house. The goal is to keep them out before fall and remove them without making them stink.
The stink bug calendar #
| Time of year | What stink bugs are doing | What you’ll notice |
|---|---|---|
| Late April to mid-May | Leaving winter shelter | Bugs at windows and lights, trying to get out |
| Summer | Feeding and breeding outdoors on fruit, vegetables and trees | Damage on tomatoes, peppers, apples, peaches, beans |
| September to October | Searching for places to overwinter | Clusters on sunny, south- and west-facing walls; bugs coming indoors |
| Winter | Dormant in walls and attics | Occasional sluggish bugs on warm days |
This timing comes from Penn State Extension, which reports that adults begin looking for overwintering sites from September through October and emerge in spring from late April to mid-May. The exact weeks shift with latitude and weather, and a warm fall can stretch the season.
Which stink bug is in my house? #
The stink bug that invades homes in large numbers in North America is almost always the brown marmorated stink bug (BMSB), an insect from East Asia that arrived in eastern Pennsylvania in the 1990s and has spread widely since.
How to recognize it, per Penn State:
- About 17 mm (2/3 inch) long, shield-shaped and mottled brown
- Light bands on the antennae, the easiest feature to check
- Alternating light and dark bands along the edges of the abdomen, visible beyond the wings
- Smooth, rounded “shoulders” (native brown stink bugs often have pointier ones)
Native stink bugs, such as the green stink bug and various brown species, feed outdoors too but rarely pile into houses the way BMSB does. One native lookalike, the spined soldier bug, is actually a predator of pest insects and has sharp spines on its shoulders.
Other fall invaders that get called stink bugs #
- Western conifer seed bug: brown, longer and narrower, with flattened leaf-like flares on its hind legs
- Boxelder bug: black with red-orange lines, gathers on sunny walls near boxelder and maple trees
- Kudzu bug: small, olive-brown and squarish, common in the Southeast near kudzu and soybeans
- Asian lady beetle: round, orange to red, with an M mark behind the head; see Asian lady beetle vs ladybug
All of these come in for the same reason, and the same prevention steps work on all of them.
Are stink bugs harmful? #
Not to people or pets in any serious way. Penn State notes that brown marmorated stink bugs don’t bite. Their defensive odor comes from glands on the body and is released when they’re crushed or disturbed. Some sensitive people have allergic reactions to them, and crushing one on the skin can cause irritation where it touches.
They don’t reproduce inside homes, don’t eat anything indoors, and don’t damage wood, fabric or food. The damage they do happens outdoors, where they feed on fruit, vegetables and ornamental trees.
How to keep stink bugs out before fall #
Penn State calls mechanical exclusion the best method of keeping stink bugs out of homes. Do it in August or early September, before the bugs start moving.
- Caulk cracks around windows, doors, siding, trim, chimneys and utility lines.
- Repair or replace damaged screens on windows, doors and attic vents.
- Seal gaps around window air conditioners, or remove the units before fall.
- Install door sweeps and check weatherstripping.
- Screen attic, soffit and dryer vents with fine mesh.
- Check where pipes, cables and faucets enter the house and fill the gaps with sealant or expanding foam.
South- and west-facing walls warm up fastest in fall afternoons and attract the most bugs, so start there.
How to get rid of stink bugs inside #
- Vacuum them up. Penn State recommends using a vacuum for bugs in living areas. Empty it outside afterward, or use a bag you can throw away, because the vacuum will smell for a while.
- Drop them into soapy water. Knock bugs from walls and curtains into a container of water with a squirt of dish soap. It avoids the smell of crushing them.
- Don’t crush them indoors. That releases the odor.
- Skip indoor insecticides. Penn State advises against them. Killing bugs inside walls leaves dead bugs that can attract carpet beetles, which then feed on other things in your home.
- Light traps in attics or dark rooms can catch wanderers in spring.
Exterior insecticide treatments around windows in early fall are sometimes used by pest professionals, but they break down in sunlight and don’t replace sealing.
Stink bugs in the garden #
Outside, the summer season is when stink bugs do their damage. They pierce fruit and vegetables and suck the juices, leaving dimpled, corky or discolored spots on tomatoes, peppers, apples, peaches and sweet corn. Hand-picking into soapy water, row covers over young plants, and removing weedy hosts near the garden help. Your state’s Cooperative Extension office has current guidance for fruit and vegetable growers in your area.
Confirming it’s a stink bug #
A quick photo from above, with the antennae in view, is usually enough. Insect Identity recognizes the brown marmorated stink bug, green stink bug, southern green stink bug, green shield bug and harlequin bug, plus fall invaders often mistaken for them: the kudzu bug, eastern boxelder bug and western conifer seed bug. It gives a best match with a confidence score and four runners-up, runs offline, and keeps the photo on your phone. For roach-like fall visitors, see bugs that look like cockroaches, and for anything else on the windowsill, what is this bug in my house.
Frequently asked questions #
What month do stink bugs come out? #
Indoors, they’re most noticeable in September and October as they move in, and again from late April to mid-May when they emerge from hiding and head for windows. Outdoors, adults are active from spring through fall.
Why are there so many stink bugs in my house in winter? #
They got into your walls and attic in the fall and are spending the winter there. On warm, sunny days, some wake up and wander into rooms, drawn to light and warmth. Sealing entry points next summer is the long-term fix.
Do stink bugs lay eggs in your house? #
No. Stink bugs that overwinter indoors don’t mate or lay eggs inside. They leave in spring to feed and breed outdoors.
What smell keeps stink bugs away? #
No scent is proven to reliably keep stink bugs off a house. Home remedies like mint oil sprays aren’t a substitute for sealing cracks and repairing screens, which is what extension entomologists recommend.