Stink Bugs Getting In Every Fall?

Every September they pile onto the sunny side of the house, and by October they're on the window frames, in the curtains, and behind the shower curtain rod. Here's the thing that changes the outcome: this is an outdoor problem with an indoor symptom. Treat the exterior before they move in and you get a quiet winter. Wait until they're in the walls and there's very little anyone can do.

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First: The Timing Is the Whole Thing.

Stink bugs don't breed in your house. They come in from outside, all at once, over a few warm days in autumn, looking for somewhere sheltered to spend the winter. Then they sit dormant in wall voids, attics, and around window frames until warmth wakes them up — which is why you get a fresh wave every sunny day in February, and why people think they're multiplying in there. They aren't. They're the same ones, waking up in shifts.

The window that matters is late September into early October in Central PA — as they start massing on warm walls, before the first real cold snap drives them through the gaps. An exterior application then intercepts them on the siding. The same application in December, once they're behind your drywall, mostly doesn't reach them.

Pennsylvania Didn't Get Unlucky — It Got Them First

Worth knowing, because it explains why this is worse here than most places. The brown marmorated stink bug arrived from Asia and the first established U.S. population was identified in the Lehigh Valley in the late 1990s. Everything since has spread outward from eastern Pennsylvania. We've had them longer than nearly anywhere in the country, and the populations in the Susquehanna Valley reflect that. If it feels like your house gets more than it should, it probably does.

The Four That Do This

They arrive at the same time of year, for the same reason, and the treatment approach is the same for all of them — but it's useful to know which you have.

Brown marmorated stink bug

Shield-shaped, mottled brown, about the size of a fingernail, with pale banding on the antennae and the edge of the abdomen. Clumsy fliers that buzz into lampshades. The smell is the defence — release it when threatened or crushed.

Boxelder bug

Slim, black, with bright red-orange lines on the back. Gathers in large numbers on warm walls, often near boxelder or maple trees. Harmless, but they arrive in real numbers and they stain surfaces when squashed.

Asian lady beetle

Looks like a ladybug but varies from orange to deep red, usually with an M-shaped mark behind the head. These do occasionally bite, and they leave a yellow staining fluid on walls and curtains.

Cluster fly

Larger and more sluggish than a house fly, with golden hairs on the thorax. Clusters in attics and around upper windows. Turns up in numbers on warm winter days for the same reason as the others.

None of these will hurt your house They don't bite (with the occasional exception of lady beetles), they don't breed indoors, they don't eat structural wood, and they don't infest food. This is a nuisance problem, not a damage problem. It's just a nuisance problem at a scale that makes people want to move.

How We Treat It

We're a perimeter-based company — we don't spray inside. On this pest that isn't a limitation, it's the correct method. Treatment is a thorough exterior application to the surfaces they actually gather on and enter through: the sunny south and west walls, around window and door frames, soffit and fascia lines, utility penetrations, vents, and the foundation band. Timed to early autumn, that intercepts them at the point of entry.

Where a property gets hit hard every year, the more sensible answer is the monthly perimeter program, which puts the autumn treatment on the calendar automatically along with the rest of the seasonal perimeter work — you stop having to remember it in the middle of September.

Cost: single treatments run $100–$250 depending on the pest and the property. The monthly perimeter program runs $70–$100 a month, March through November. If you already have an active infestation over the winter, that is separate work and we do come out for it. Free estimates, and no contract on any of it.

The Part Treatment Can't Do

Exclusion. It's unglamorous and it's permanent, and on a house that gets overwhelmed every year it's worth as much as the spraying:

Please Don't

Where We Cover

All of the City of Harrisburg (17101–17104, 17109, 17110) plus Penbrook, Paxtang, Steelton, Highspire, Colonial Park, Lower Paxton, Susquehanna Township, and Linglestown. Also Hershey, Hummelstown, Mechanicsburg, Camp Hill, Palmyra, Middletown, Carlisle, and Lebanon.

Frequently Asked Questions

It's February and they're everywhere. Can you come now?
Yes — active winter infestations are work we do take, and if you are living with them now you should not have to wait until autumn. Be clear on what it can and can’t do: the ones you are seeing are already inside the structure, so this is about knocking down what is there rather than preventing what already got in. Log homes especially get treated through the winter, because the log seams and the sun-warmed south wall keep pushing them into the living space all season. The high-value move is still getting on the calendar for late September so next winter is quiet — but we will come out now.
Why won't you spray inside?
Two reasons. It's our policy generally — we're a perimeter-based company and we don't spray interiors. And on this pest specifically it wouldn't achieve much: the insects are in wall voids and attic spaces rather than out on the surfaces you'd treat, and killing large numbers inside a wall creates a secondary problem with beetles that feed on the remains. The effective work is genuinely all outside.
Will one treatment solve it?
It makes a substantial difference in the year it's applied, correctly timed. It isn't permanent — the treatment weathers, and next autumn brings a new wave from outside. Properties that get hit hard do better on the monthly program plus some exclusion work, which together take it from an infestation down to the occasional bug on a windowsill.
Are they dangerous to my kids or pets?
No. They don't bite (the odd Asian lady beetle aside), they carry nothing, and they don't damage the house. A dog that eats one will usually make a face and possibly drool, and that's the extent of it. Unpleasant, not hazardous.
What else do you handle?
Other perimeter work: pest control in Harrisburg, carpenter ants, and stinging insects. If something is getting into the attic rather than the walls, see squirrels, bats, or raccoons. There's a longer read on stink bugs and boxelder bugs as fall invaders.

Get on the Calendar Before Late September.

That's the whole trick with fall invaders — the treatment has to land before they move in, not after. Call or text and we'll book the right window for your property. Perimeter-based, no indoor spraying, no contracts. Licensed PA pesticide applicator since 2005, fully insured, locally owned.

Call or Text 717-379-3248