How to keep stink bugs out of your house this fall

Seal the cracks on the outside of your house before late August, and skip the bug spray. Brown marmorated stink bugs head for homes starting in September and look for a warm spot to spend the winter. Blocking their entry points now beats fighting them later (Purdue Extension).

The good news is these bugs are a nuisance, not a threat. They don't bite, sting, spread disease, or chew your walls, and they won't reproduce inside your house (NC State Extension, Michigan State Extension).

Why they show up in fall

These bugs are an invasive species from eastern Asia. They first turned up in Pennsylvania before 1998, and in North Carolina in 2009 (Purdue Extension, NC State Extension).

Adults measure about 1/2 to 3/4 inches long. You can spot them by the dark and light bands alternating on the last two antenna segments. They don't feed or breed indoors; the ones in your house are just overwintering. By summer, most move back outside to feed and mate in woods and gardens (Purdue Extension).

Watch the outside of your home in September and October. If you see clusters of stink bugs on the siding, the ones you can't see are likely already headed indoors (Michigan State Extension).

Seal them out before late August

Blocking them out physically is the best way to keep stink bugs away, and the timing matters. Adults squeeze through holes as small as 3x7mm, so check the gaps around windows, doors, vents, and siding (NC State Extension).

Caulking exterior cracks reduces entry on homes with wooden siding. Caulk won't work fully on vinyl siding, though, because the panels are loose-nailed and built to move (Purdue Extension).

Sealing at the wrong time can backfire. If you seal the house in fall, winter, or early spring, you can trap bugs inside the walls with you. Let them escape in spring instead, then seal the entry points before they return in late August.

Skip the spray

A single insecticide application rarely lasts, because stink bugs can fly several miles and fresh ones keep arriving from outside (Michigan State Extension). Indoors, sprays often fall short too, since the bugs move around and the mist contaminates your living space (NC State Extension).

Pyrethroid insecticides work best against stink bugs, but they also kill helpful insects, so save them for severe infestations. In practice, exclusion and removal do most of the work.

Get rid of the ones already inside

Don't squash them. Agitating or crushing a stink bug worsens the smell, since the insect releases a foul chemical from scent glands when disturbed. An undisturbed bug rarely stinks, but many distressed bugs in an enclosed space can produce a smell you can't live with (NC State Extension).

Instead, capture them. Drop each bug into a jar and freeze it, or drown it in soapy water. If you use a vacuum, dedicate one to stink bug duty and freeze the bag's contents afterward. Live-releasing them outdoors doesn't work either; the odds are good they'll walk right back in.

A simple trap works at night. Set a desk lamp so it shines into a pan of soapy water; bugs drawn to the light fall in and drown (Purdue Extension).

Two more reasons to sweep them out rather than ignore them. Large numbers of dead stink bugs in attics, walls, or crawl spaces can attract secondary pests such as carpet beetles (NC State Extension).

In areas with very high stink bug numbers, they can also crowd into small engines and heat pumps in groups big enough to cause malfunctions.

Your fall checklist

Mark late August on the calendar and walk the outside of your house then. Caulk the cracks on wooden siding, and check the gaps around windows and doors.

Come September, sweep up strays with a jar and soapy water, and skip the indoor sprays (Purdue Extension). Do the sealing once in late summer, and next winter will be quieter than this one (NC State Extension).