Stink bugs invade Pennsylvania and New Jersey homes in late summer for one reason—they are searching for a protected place to survive winter.
Starting in late August and peaking through September and October, brown marmorated stink bugs gather on warm, sunny exterior walls and slip inside through gaps around windows, siding, and soffits.
The fix is timing. Sealing your home’s exterior before the September rush keeps them out, because once stink bugs settle into wall voids and attics, no spray reaches them and they will reappear indoors all winter and spring.
A year-round Home Protection Plan covers stink bugs along with more than 40 other household pests, with treatment timed to this exact seasonal window.
Here is what stink bugs are, why they pick your house, and the nine steps that actually keep them out.
What Exactly Are Stink Bugs?
The stink bug invading NEPA homes is the brown marmorated stink bug (BMSB), a shield-shaped, mottled-brown insect about five-eighths of an inch long.
It gets its name from the odor glands it uses as a defense, which release a pungent smell when the bug is crushed or threatened.
This is an invasive Pennsylvania story. According to Penn State Extension, the brown marmorated stink bug was first collected in the United States in Allentown in 1998 after arriving from Asia.
It has since spread across the country, and researchers track its range and crop damage through the USDA-supported project at StopBMSB.org.
Two facts homeowners should know. Stink bugs do not bite, sting, or damage the structure of your home. And they do not breed indoors during winter; the bugs you see in January entered in the fall.
Why Do Stink Bugs Invade Homes in Late Summer?
Stink bugs invade in late summer because shortening days and cooling nights trigger their search for overwintering shelter. In nature, that shelter is a rocky outcrop or dead tree. In a neighborhood, it is the sunny south or west wall of your house.
Homes with certain features get hit hardest. Light-colored siding, wooded lots nearby, and lots of exterior cracks all increase landings.
Stink bugs also release an aggregation pheromone once they find a good site, which is why one house on the block can be covered while a neighbor sees only a few.
Stink Bug Fall Invasion Timeline (NEPA)
| Time of Year | What Stink Bugs Are Doing | What You Should Do |
|---|---|---|
| Early to mid August | Feeding outdoors; first scouts appear on warm walls | Start exterior sealing now, before the rush |
| Late August to September | Mass landings on sunny south- and west-facing walls | Finish sealing; schedule an exterior barrier treatment |
| October | Peak indoor entry through gaps and vents | Vacuum up any bugs that get inside; keep screens tight |
| November to February | Dormant in wall voids, attics, and window frames | Do not treat inside walls; remove stragglers by vacuum |
| March to April | Waking bugs emerge into living spaces, seeking a way out | Vacuum and release outdoors; plan next fall’s sealing |
The takeaway from the timeline: August is the action month. Everything gets harder once the bugs are inside your walls, so this piece of fall pest prep cannot wait until October.
How to Keep Stink Bugs Out: 9-Step Exclusion Checklist
Exclusion beats extermination for stink bugs. The EPA’s guidance on the brown marmorated stink bug emphasizes sealing and mechanical removal over indoor spraying, and our technicians follow the same logic.
Work through these nine steps before Labor Day:
- Caulk around window and door frames: These perimeter gaps are the number one entry point.
- Repair or replace damaged screens: Check porch, window, and attic vent screens for tears.
- Seal utility penetrations: Caulk around pipes, cables, and AC line entries.
- Add door sweeps and weatherstripping: Daylight under a door is an open invitation.
- Screen attic and crawl space vents: Use fine mesh; stink bugs exploit louvered gable vents constantly.
- Inspect siding, soffits, and fascia: Seal gaps where trim meets siding, especially on south- and west-facing walls.
- Cap the chimney: An open flue is a highway into the living room.
- Turn off unnecessary exterior lighting in September: Lights attract stink bugs to the walls at night. Swap bright white bulbs for yellow ones where lighting is needed.
- Schedule a professional exterior treatment in late August: A timed barrier treatment on landing surfaces intercepts stink bugs before they find a gap. This is the step that protects the entry points you cannot see or reach. Our residential pest control team times these treatments to the NEPA invasion window.
Why You Should Never Squish a Stink Bug
Do not squish stink bugs, for two reasons. First, the obvious one: crushing them releases the foul odor they are named for, and the smell lingers on hands, walls, and carpet.
Second, the smell can make the problem worse. The defensive odor can signal other stink bugs and, in the case of the aggregation pheromone left at a good overwintering site, can help mark your home as a destination.
The right removal method is a vacuum. Vacuum the bugs up, then empty the canister or discard the bag outside promptly so the odor does not spread through the machine. For a handful of bugs, a jar of soapy water works: knock them in, and they sink.
One more warning: do not fog or spray inside your walls. Killing large numbers of overwintering bugs inside wall voids leaves carcasses that attract carpet beetles and other secondary pests, trading one problem for two. Our Stink Bug FAQ covers more of these common mistakes.
When Should You Call a Professional for Stink Bugs?
Call a professional if you are seeing dozens of stink bugs on exterior walls in September, finding them indoors daily in October, or dealing with repeat invasions every year. Heavy recurring pressure means your home sits in a high-traffic flight path, and the answer is a properly timed exterior treatment plus exclusion, not indoor sprays.
Stink bugs also rarely arrive alone. The same gaps that let them in admit mice heading indoors on the same fall schedule, so one exclusion effort protects against both.
Every Pest Rangers technician is licensed by the Pennsylvania Department of Agriculture, treatments are timed to the NEPA invasion window, and if a covered pest returns between visits, so do we, free.
FAQs
What attracts stink bugs to my house?
Warm, sunny south- and west-facing walls, light-colored siding, exterior lighting, nearby trees, and accessible gaps around windows, siding, and vents. Once early arrivals find a good site, their aggregation pheromone draws more.
Are stink bugs harmful to people or pets?
No. Brown marmorated stink bugs do not bite or sting, and they do not damage the structure of homes. They are a nuisance pest indoors, though their odor can irritate sensitive noses, and pets that mouth them get a foul-tasting surprise.
How do I get rid of stink bugs already in my house?
Vacuum them up and empty the canister outside immediately, or knock them into soapy water. Avoid crushing them, and avoid indoor sprays or foggers, which do not reach the wall voids where the bugs actually overwinter.
When is the best time to treat for stink bugs in PA?
Late August through early September, before mass entry begins. An exterior barrier treatment applied to landing surfaces in that window intercepts stink bugs before they get inside, which no amount of winter spraying can fix afterward.
Why do stink bugs keep appearing inside all winter?
The bugs entered in fall and settled into wall voids and attics. On warm winter days they wake and wander into living spaces, often near windows and lights. Vacuum them as they appear, and focus on sealing before next fall.
