pest-control
Stink Bugs and Boxelder Bugs: Michigan's Fall Invaders
Stink bugs, boxelder bugs, and Asian lady beetles invade Michigan homes each fall. Learn how to tell them apart, seal entry points, and time treatment right.
In This Article
Stink Bugs and Boxelder Bugs: Michigan's Fall Invaders
Every September, Michigan homeowners start finding the same two bugs on their window screens. One is a flat, shield-shaped brown insect that smells awful when you squash it. The other is a narrow black bug with red-orange lines that piles up by the hundreds on the sunny side of the garage.
These are the brown marmorated stink bug and the boxelder bug. They don't bite people, they don't eat your house, and they don't breed indoors. They do slip into walls and attics to spend the winter, then wander into living rooms on warm days in February and March.
If you live in Grand Rapids, Lansing, or the suburbs north and west of Detroit, the best time to stop them is weeks before you see the first one.
Telling the Two Pests Apart
Most people lump every fall bug into one category, but these two behave differently and respond to slightly different defenses. Knowing which one you have tells you where to look for entry points and when to schedule treatment.
A quick look is usually enough. Stink bugs are wider and mottled brown, and boxelder bugs are slimmer with clear red markings on a black body.
Brown Marmorated Stink Bug
This stink bug came to the United States from Asia and spread through the Midwest over the last couple of decades. In Michigan it is now common across the Lower Peninsula, with the heaviest pressure near orchards and farm fields in west Michigan, where it feeds on apples, peaches, and sweet corn. Adults are a little over half an inch long with banded antennae and a marbled brown back.
When disturbed or crushed, they release a sharp odor that many people compare to cilantro or old gym socks. That smell is the main complaint indoors. They also tend to drop off curtains and buzz loudly around lamps in the evening.
Boxelder Bug
Boxelder bugs feed mostly on the seeds of female boxelder trees, and they also visit silver maples and some ash. They are about half an inch long, black, with three red stripes behind the head and red edging along the wings. Young nymphs are bright red and show up in summer clusters on tree trunks.
Their droppings can leave small reddish stains on light curtains and siding. A home near a stand of boxelder trees, which grow along creeks, fence rows, and vacant lots all over southern Michigan, can see huge numbers on a single warm afternoon.
| Trait | Brown Marmorated Stink Bug | Boxelder Bug |
|---|---|---|
| Shape | Wide, shield-shaped | Narrow, elongated |
| Color | Mottled brown | Black with red-orange lines |
| Main food source | Fruit, vegetables, ornamentals | Boxelder and maple seeds |
| Odor when crushed | Strong | Mild |
| Stains | Rare | Reddish spots on fabric |
| Favorite hiding spot | Attics, wall voids, window frames | Siding gaps, foundation cracks, wall voids |
The Third Bug on Your Siding
Multicolored Asian lady beetles join the fall crowd almost every year in Michigan. They look like ordinary ladybugs, but the color ranges from pale yellow to deep orange and the number of spots varies a lot. The easiest field mark is a small black "M" or "W" shape on the white area behind the head.
These beetles were released decades ago to control aphids and they still do that job well outdoors. Indoors they are a nuisance. They can give a small pinch on bare skin, and when stressed they leak a yellow fluid that smells bitter and can stain painted trim.
Lady beetles favor the same places as the other two invaders. A light-colored house with a sunny south or west wall near a wooded lot is a magnet for all three, which is why most Michigan pest control companies treat them as one fall problem with one plan.
Where Michigan Homes Get Hit Hardest
Location shapes how bad your fall gets. Homes on the edge of open country usually see more stink bugs, while homes in older neighborhoods with mature trees tend to see more boxelder bugs and lady beetles.
Around Grand Rapids, MI, the orchard belt north of the city known as the Fruit Ridge keeps stink bug numbers high, and suburbs like Walker, Comstock Park, and Sparta often feel it first. In the Lansing area, homes in Okemos, Haslett, and DeWitt that back up to farm fields or tree lines report heavy lady beetle swarms in October. The Detroit suburbs are a mixed bag: Troy, Novi, and Rochester Hills see plenty of boxelder bugs where silver maples line the streets, and newer subdivisions near open land in Macomb and Oakland counties get stink bugs moving in from fields.
House style matters too. Older homes with wood or aluminum siding, loose window trim, and unscreened attic vents give bugs dozens of ways inside. Newer vinyl homes are tighter, but the gaps around dryer vents, cable lines, and soffit returns are still easy entry points.
Sealing the House Before They Arrive
Exclusion is the cheapest long-term fix, and it works against all three pests at once. A stink bug can squeeze through a gap about an eighth of an inch wide, so look for anything you can slide a credit card into.
Start on the south and west sides, since those walls warm up first and attract the most bugs. Work from the roofline down to the foundation, and do it on a dry day in August so caulk cures well. These are the spots that matter most:
- Gaps where siding meets window and door trim
- Torn screens and window air conditioner openings
- Attic, gable, and soffit vents without fine mesh
- Holes around dryer vents, hose bibs, cable lines, and gas meters
- Worn door sweeps and garage door bottom seals
- Gaps where the chimney meets the siding
Use a good exterior silicone or polyurethane caulk for narrow cracks and copper mesh or foam backer rod for wider holes. Fine mesh screen over vents keeps bugs out without blocking airflow, which matters for attic moisture during a Michigan winter.
A professional exclusion job usually costs roughly $300 to $1,500 depending on the size of the house and how much trim work is needed. Many homeowners handle the easy items themselves for about $50 to $150 in caulk, sweeps, and screen, then hire out the high rooflines.
Timing a Perimeter Treatment in Late Summer
Spraying in October is the most common mistake Michigan homeowners make. By then the bugs are already inside the walls, and the spray only hits the stragglers.
The better window runs from late August through about mid-September, before the first cold snap. Stink bugs, boxelder bugs, and lady beetles start gathering on warm walls after the first few nights in the 40s. A residual treatment applied before that point is waiting for them when they land.
Technicians typically use a pyrethroid or similar residual product on the south and west walls, around windows and doors, along the eaves, and in the gap where the foundation meets the siding. One application can hold for several weeks in dry weather. Heavy September rain or a long warm fall may call for a second visit in early October.
In the Upper Peninsula and northern Lower Michigan, cooler nights arrive earlier, so the window shifts toward mid to late August. Around Detroit and Lansing, early September is usually the sweet spot.
What Fall Pest Control Costs in Michigan
Prices vary by company and house size, but most Michigan homeowners pay in a fairly predictable range for occasional invader work. The table below shows roughly what to expect.
| Service | Typical Cost Range |
|---|---|
| One-time exterior perimeter treatment | About $150 to $350 |
| Two-visit fall program (late August and October) | About $250 to $500 |
| Professional exclusion and sealing | About $300 to $1,500 |
| Add-on to an existing quarterly plan | About $50 to $125 per visit |
| DIY sealing supplies | About $50 to $150 |
Homes with steep roofs, three stories, or heavy tree cover tend to land at the top of those ranges because the eaves take longer to treat. If you already pay for a general pest plan, ask whether a fall occasional invader treatment is included before buying a separate service.
The best value for most houses is a combination: seal the easy gaps yourself in August, then pay for one well-timed exterior treatment. That approach tends to cut the number of bugs inside by a wide margin compared to spraying alone.
Handling the Ones That Get In
Even a well-sealed house will see a few bugs on warm winter days. They are not reproducing indoors. They are waking up in the walls and following warmth and light toward the living space.
A shop vacuum or a vacuum with a disposable bag works best. Empty it outside right away, since crushed stink bugs will make the vacuum smell for days. Avoid swatting lady beetles on painted surfaces, because the yellow fluid can leave a stain.
Skip foggers and indoor sprays for these pests. Killing bugs inside wall voids leaves dead insects that attract carpet beetles and other scavengers later. A simple light trap near an attic window can catch a lot of stragglers through late winter.
If the bugs are pouring out of one spot, like a ceiling light or a bathroom fan, that is a sign of a gap in that area. Mark it and seal it the next summer. You can read more seasonal guides on our home services blog for Michigan homeowners, and when you are ready to bring someone in, compare local pest control companies across Michigan that offer late summer treatments.
Frequently Asked Questions
Are stink bugs or boxelder bugs dangerous to pets?
Neither bug is poisonous to dogs or cats. A pet that eats several stink bugs may drool or vomit because of the bitter taste, but that usually passes within a few hours.
Should I cut down the boxelder tree in my yard?
Removing a female boxelder tree near the house can lower boxelder bug numbers, but bugs can fly in from trees several blocks away. In older Detroit suburbs with lots of silver maples, sealing and timed treatment usually do more than removing a single tree.
Why are the bugs back every year even after treatment?
These insects use the same warm walls year after year, and new adults arrive from fields and trees each fall. One treatment covers one season, so most Michigan homes need a fresh application every late August or September.
When do the bugs show up inside during winter?
Most indoor sightings happen on sunny days between about January and April, when the attic or wall warms up. A string of 40 and 50 degree days in March is when many Lansing and Grand Rapids homeowners see the most.
Can I use dish soap and water on them?
A bucket of soapy water works well for knocking boxelder bugs and lady beetles off siding by hand. It only kills the bugs it touches, so it is a cleanup method and won't keep new arrivals away.