Stink bugs in the house: why they come in during autumn and how to remove them

Stink bugs usually turn up indoors in autumn. Adults look for a dry, sheltered place to spend the winter and get into buildings through gaps around windows, doors and walls. This is a seasonal event, not an emergency.

Stink bugs do not bite people or pets, are not venomous, and do not breed in the house. The real nuisance is the smell and the numbers. Do not crush them: collect them in soapy water or with a vacuum, then find and seal the gaps they use to get in.

This guide deals with the household problem. Identification, biology, distribution in Georgia and crop damage are covered on the species profile: brown marmorated stink bug (Halyomorpha halys). Other stink bugs can also look brown at first glance; the profile explains the field marks.

The brown marmorated stink bug spends the winter as an adult. In autumn, as days shorten and temperatures drop, adults look for a dry, protected overwintering site. In a laboratory study of the invasive population in the Caucasus, short days induced winter diapause, a pause in reproduction, in all adults.

Outdoors, such shelter is a tree hollow or a thick layer of fallen leaves; in a settlement, it is a building. Stink bugs can get into attics, gaps in window and door frames, cracks in walls and foundations, under the roof edge, around chimneys, and where pipes or cables pass through a wall.

Indoors, a stink bug is only sheltering and does not damage the house. In the cold its activity slows down sharply until spring.

According to Georgia's National Food Agency, stink bugs feed on plants from late April or May until late autumn and move into residential buildings as it gets colder. Official sources do not give one exact date for every region: timing depends on the weather and the location.

In winter, overwintering stink bugs are mostly inactive. On warm, sunny days or when the house is heated strongly, some wake up and crawl slowly, often in bathrooms and kitchens, by window and door frames, along baseboards, or around ceiling lights. That is why you may see a stink bug on a window in the middle of winter.

In spring, as it warms up, stink bugs leave houses and abandoned buildings and return outdoors to feed on plants.

Normally, no. According to guidance from Georgia's National Center for Disease Control and Public Health (NCDC), the stink bug is not venomous, does not bite people or pets, and does not transmit human or animal diseases. It does not sting either.

Indoors it is a nuisance, not a medical threat. Some people may be sensitive or allergic to its defensive secretion, but NCDC does not describe this as life-threatening. If you notice a reaction after contact with the insect, ask a doctor for advice.

No. According to university extension services (Penn State Extension, UMN Extension), stink bugs that come indoors do not lay eggs or reproduce over the winter; they are in a dormant state. Stink bugs seen indoors in spring are usually the same adults that came in during autumn.

Reproduction happens outdoors in the active season. Georgia's National Food Agency describes egg clusters laid on the underside of leaves, with nymphs developing on plants.

So if many stink bugs appear every autumn, that means new arrivals from outside rather than breeding indoors, and the main solution is to seal entry points.

The smelly substance is the stink bug's defence: it releases it to deter predators, especially when disturbed, handled or crushed.

Crushing one indoors makes the smell stronger, and it can linger on surfaces; a vacuum cleaner may also smell for a while. The odour does not attract other stink bugs, but it is unpleasant, so it is better to remove the insect whole, without crushing it.

The safest way to remove stink bugs indoors is mechanical, without chemicals. Georgia's National Food Agency also recommends mechanical methods for stink bugs that have entered homes, such as sweeping them off walls and collecting them with a vacuum cleaner.

1. Prepare a container with water and a little liquid soap or detergent at the bottom. A stink bug that falls into soapy water cannot climb out.
2. Hold the container under a bug on a window, wall or curtain and brush it in with a piece of cardboard or a small brush. You can also pick up a single bug with paper; the key is not to crush it.
3. For many stink bugs, use a vacuum cleaner. To reduce the smell, some people fit a nylon stocking inside the hose: the bugs stay in the stocking instead of reaching the bag, and are then emptied into soapy water.
4. After use, empty and clean the vacuum bag or canister. The smell is temporary.
5. If stink bugs emerge indoors around baseboards, window and door trim, or ceiling lights and exhaust fans, seal those openings as well so they cannot crawl out of the walls into living space.

The most effective and lasting way to protect a home is to seal entry points, known as exclusion. It is best done before autumn, before stink bugs start looking for shelter.

• Window and door frames: fill gaps and cracks with good-quality silicone or silicone-latex caulk; expanding foam can be used for larger gaps.
• Screens: window and door screens should fit the frame tightly; repair or replace damaged ones.
• Pipes and cables: seal the openings where pipes, wires and cables enter the wall.
• Walls and roof: check cracks in the foundation and walls, siding, the roof edge and the underside of the eaves, as well as chimneys and fireplaces.
• Vents: cover vents with screening instead of blocking them, so air can still move.
• Cardboard shelters: Georgia's National Food Agency describes a simple shelter made of cardboard egg-tray sheets placed near the house. Stink bugs looking for overwintering sites gather in it and are then destroyed mechanically.

Some quick fixes do not solve the problem or create a new risk.

• Do not crush large numbers of stink bugs indoors: the smell gets stronger and stays on surfaces.
• Do not make homemade chemical mixtures, and never mix household chemicals together.
• Do not use agricultural pesticides indoors. Indoor aerosols or foggers only kill the bugs sitting in the open; those hidden in cracks come out later anyway.
• Do not spray insecticide into wall voids or the attic: dead stink bugs can attract carpet beetles, which may then damage woollens and stored dry food.
• Do not use any product against its label directions or use an unregistered product.
• Do not treat a stink bug sighting as a medical emergency: it does not bite and is not venomous.

A few stink bugs do not require a professional. Professional help makes sense if very large numbers get in every autumn, if entry points are out of reach, for example high on a wall or near the roof, or if you cannot find where they are getting in.

A pest control service can treat the outside of a building in autumn, before mass entry. However, Penn State Extension notes that such treatment gives only minor relief: sunlight breaks the product down, and the effect may not last beyond several days or about a week. It does not replace sealing entry points.