The first one usually appears on a warm afternoon in late September, crawling up the inside of a sunny window. A week later there are three on the curtain and one on the lampshade. Across much of the country, the brown marmorated stink bug is moving indoors right now, and the reflex almost everyone has the first time they see one is exactly what turns a nuisance into a problem.
The insect is easy to recognize once you know it: a shield-shaped body about five-eighths of an inch long, mottled brown and gray, with white bands on the antennae. It is not the kind of bug you should panic about. It is the kind you should handle differently.
Why they’re in your house this month
Native to Asia and first identified in eastern Pennsylvania, the brown marmorated stink bug has since spread to nearly every state, with the heaviest populations along both coasts and in the Midwest. It feeds on fruit, leaves and garden crops all summer.
Then, as nights cool down, adults gather and look for a sheltered place to spend the winter, and buildings are their favorite. On warm fall days, sun-facing walls, windows and doors are where they cluster and slip in. Once inside, they live off stored energy and can survive without food until spring. They don’t reproduce indoors.
The reassuring part, according to the University of Maryland Extension: they don’t bite, sting or spread disease, and they don’t eat or bore into wood. Don’t count on the first frost to get rid of them, either. Entomologists at Virginia Tech found they could survive temperatures below -4°F.
The mistake: squashing them
The instinct is to crush the bug with a tissue or a shoe. That is precisely what triggers the defensive odor that gave it its name. The smell fades after a while, but crushed bugs can also stain walls and curtains, and in some sensitive people the odor causes allergic reactions such as a runny nose or irritated eyes.
The second mistake is reaching for an indoor insecticide. Experts at Penn State advise against it: it doesn’t solve the problem, and dead stink bugs left in walls and corners can attract carpet beetles, which then feed on them.
What works instead
The simplest method takes advantage of the bug’s own reflex: when disturbed, it drops straight down. Hold a container of soapy water under it and tap it gently. It falls in, can’t climb out, and drowns without releasing its smell. They are slower on cool, overcast days, which makes them easier to catch.
For larger numbers, a vacuum works, but empty it outdoors right away, because the bugs will release their odor inside it.
Keeping the next ones out
Prevention does more than any trap. Seal cracks around windows, doors, siding, utility pipes and chimneys with silicone caulk, repair torn screens, and add a door sweep to exterior doors. Doing it now, before the peak of the season, keeps most of them outside.
Stink bugs aren’t the only visitors looking for a warm place this time of year, and not all of them are bad news: sometimes the spider in the corner is doing you a favor.
A cup of soapy water on the windowsill and a tube of caulk: that’s the whole fall routine. That’s the trick.
