Brown marmorated stink bugs enter homes in fall to find winter shelter, not food. Sealing cracks and gaps before the flight is the lasting fix, and the insects inside can be vacuumed or released outside. They do not bite.
Key takeaways
- The stink bugs that enter in fall are looking for a place to spend the winter, so they are attracted to the outside of the building first.
- Caulking, weather-stripping and removing window air conditioners are the University of Maryland Extension's steps for keeping them out.
- Vacuuming or releasing them outdoors is the practical way to clear the ones already inside, and they do not bite.
- Sealing is most useful before the flight begins, which the state's agriculture department places between mid-September and fall.
- Stink bug exclusion is a visit that checks the exterior and seals the gaps a technician can reach, with the quote confirmed on site.
Why do stink bugs come indoors in the fall?
Brown marmorated stink bugs leave the landscape in fall to find shelter for the winter. A building that offers a warm, dry gap is a likely place for them to settle, and they will move in through any opening they can fit through.
The insects are not coming in for food, and they will not reproduce indoors. Their interest is shelter. As temperatures drop, they move toward structures that have a sheltered space, and a house with an open gap, a loose vent or a poor seal around a window is the kind of place they can use.
The Maryland Department of Agriculture's control material describes flights to overwintering sites that run from mid-September into October in one document and into November in another. Because the two dates differ, the timing advice on this page is given as a window rather than a single date, and the exact week depends on the weather that year.
A bug that appears indoors in late fall has usually been looking for a way in for several weeks. The number seen on a single day is a poor measure of how many are outside, and the approach that works is to shut the openings rather than to count the insects that have already got through.
Where do they get in?
Stink bugs get in through gaps that a person would not think of as a door: cracks where siding meets trim, openings around pipes and wires, loose vents and window frames. Checking those spots is more useful than searching the rooms.
The outside of the house is the best place to start. Walk the exterior slowly, paying attention to where two materials meet, such as siding against a window frame, a corner board against the siding, or a utility line entering a wall. A gap wide enough to take a thin piece of paper can be wide enough for an insect.
Vents and attic openings are often overlooked. A louvered vent with a missing screen or a bent flap gives the insects a direct route into the attic, and from the attic the rest of the house is only a few steps away. Shutters and the space behind them are another sheltered spot that can be checked from the outside.
Doors and windows need the same attention. Weather stripping that has flattened, a threshold that no longer meets the floor and a window that does not close fully all leave an opening. Window air conditioners that are left in place through the fall are a common route, which is why the University of Maryland Extension advises removing them.
Which sealing steps does the University of Maryland Extension advise?
The University of Maryland Extension advises caulking cracks, weather-stripping doors and windows, and removing window air conditioners. Those three steps are the core of keeping the insects out, and the rest of the work follows the same logic.
Caulk is the simplest tool. A small gap at a window frame, a trim joint or a penetration can be closed with exterior caulk, and the work is easy to check afterward by looking for daylight or a draft. Caulk the outside first, so the gap is closed where the insects would enter rather than just where they are found.
Weather stripping is the second step. It should close the gap at the bottom and sides of an exterior door and around the sashes of a window. Worn strips should be replaced rather than patched, because a strip that has lost its shape does not seal the gap it was installed to close.
Removing the window air conditioner is the third. A unit left in a window for the winter leaves a gap around its frame that is hard to seal properly, and it gives the insects a sheltered space behind the unit. Taking the unit out, or at least sealing the space around it, is the step the Extension advises.
What do you do with the ones already inside?
Insects already indoors can be vacuumed up or carried outside and released. They do not bite, so there is no need to handle them with more caution than a careful gather requires.
A vacuum is the simplest method for a room with a few insects. Empty the canister or bag outdoors soon afterward, because an insect left inside a vacuum can make its way out later. A stiff piece of paper or a jar works for carrying a single insect to the door.
Crushing an insect is not recommended. Many people find that a crushed stink bug gives off an unpleasant odor, which makes the job more unpleasant without solving anything. A release outside a few steps from the door is a more humane and less messy way to clear a room.
Indoor spraying is not the lasting answer. A spray may kill the insects it touches, but it does not stop the next ones from entering through the same gap. The gap is the problem, and until it is sealed, the insects will keep coming.
What does a stink bug exclusion visit cover?
A stink bug exclusion visit checks the exterior of the building for the gaps that let insects in, then seals the openings a technician can reach and advises on the rest. The written quote names the openings and the work for each.
The visit begins outside, because that is where the entry points are. The technician walks the building, notes each gap, vent and penetration, and marks which ones are sealed, which need caulk, which need a screen or a replacement and which need the homeowner's own work, such as removing an air conditioner.
The quote separates the parts of the job. Sealing gaps, replacing screens, weather-stripping doors and advising on window units are each listed, so a homeowner can see what is included. A visit that does not list the openings it will and will not seal is hard to check later.
The timing of the visit matters. A visit in late summer or early fall gives the sealing time to be finished before the flight begins, while a visit in late fall may find many insects already inside. The confirmed price is set on site, in writing, before any work starts. To book a visit, call (855) 974-4733.
Do sprays help in fall?
A spray outside can reduce some insects on the surfaces it touches, but it does not close the gaps that let new insects in. Sealing is the step that lasts, and any spray is a secondary measure.
A spray can be applied to the outside of a building in a way that reaches the surfaces where the insects land. The results are temporary, because the insects keep coming to the building through the openings that were not closed. A spray should be part of a plan that begins with sealing, not a replacement for it.
Spraying indoors is a different matter. It can leave residue on surfaces and does not address the gap that brought the insects in. A homeowner who is considering a product should ask the technician what the product is for and what it will not do.
The safest course is to close the openings first, clear the insects that are inside by vacuuming or releasing them, and then review the exterior once the sealing is finished. That order keeps the work focused on the place where the insects are coming in.
Can stink bugs appear in the middle of winter?
Yes, an insect can appear indoors on a warm winter day after it has been sheltered in a gap. Those appearances are usually a few insects rather than a new flight, and sealing the gaps remains the answer.
Stink bugs that have settled into a sheltered space can move on a warm day, and a warm room may bring them out of hiding. A single insect seen in January is not a sign that the building has been invaded again, but it is a signal that the sheltered spaces have not been closed off.
The approach is the same as in fall. Vacuum or release the insect, check the nearest gap, and seal it if it is reachable. A homeowner who keeps a note of where the insects appear can point a technician to the spots that need attention during the next visit.
The sources used for this page do not describe a winter pattern in detail, so the page does not claim one. The practical message is that a sealed building gives fewer places for the insects to stay.
What should a homeowner record during the fall?
A short fall log of when the insects appear, where they are found and what has been sealed gives a technician the information needed to close the right gaps. It also shows whether the sealing has worked by the end of the season.
Record the date each insect is found, the room and the window or wall nearest the spot. A pattern of sightings on one side of the house points the next check at that side. Sightings that stop after a seal is made suggest the seal worked, while sightings that continue in the same room suggest a route that has not yet been closed.
Note what has been sealed and when. A list of caulk joints, weather-stripped doors and removed window units shows what has been done, so a second look does not repeat the same steps. It also makes a stink bug exclusion quote easier to scope, because the technician can see which openings are already handled.
Keep the log through the winter as well. A few insects in a warm spell in January are worth noting, because the same gaps are the likely route in the next fall. The log turns a seasonal nuisance into a checklist that can be reviewed before the next flight begins.
Frequently asked questions
Do brown marmorated stink bugs bite?
No. The University of Maryland Extension says they do not bite, which is one reason a vacuum or a gentle release is the right way to clear them from a room.
Can I vacuum them without a problem?
Yes, but empty the canister or bag outdoors soon afterward. An insect left inside a vacuum can make its way out later.
Do they damage the house?
This page does not describe structural damage from these insects, because no such damage was sourced. Their concern for most homeowners is the number that appear indoors, not the condition of the building.
When should I seal the gaps?
Before the flight begins in early fall is the best time, though sealing at any point is worth doing. Mid-September into October is the window the state's agriculture department gives, and the exact week depends on the weather.
Sources
This guide is general information for Prince George's County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.