PEST CONTROL

Boxelder Bug Control in Toronto, Oakville & the GTA

Boxelder bugs, stink bugs, Asian lady beetles and other fall invaders

Boxelder bug control is mostly about timing. These black and red bugs don't bite, don't breed indoors and don't damage your home, but every fall they gather in large numbers on sunny walls, looking for a way into the walls for winter. We treat those walls in late summer, before they gather, and seal the gaps they use to get in, for homes across Toronto, Oakville and the GTA.

Clusters already on your walls? An exterior treatment can still cut down how many get in, so call as soon as they show up.

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AT A GLANCE

Boxelder Bugs at a Glance

Boxelder bug (adult)

Size: About 12 to 13 mm long
Colour: Dark brownish black with red markings
Body: Flat-backed, long and narrow
How to tell: Three red stripes behind the head, red wing edges
Active: Gathers late summer and fall; out again on warm days
Where found: Sunny south and west walls, near Manitoba maples
Bites or stings: Not known to bite people or animals

WHAT TO LOOK FOR

Signs of a Boxelder Bug Problem

If you’ve noticed any of these, call and a licensed technician will tell you what it points to.

Call (905) 739-7888

Black and red bugs clustering on sunny south- or west-facing walls in late summer and fall
Bright red, wingless young bugs on a Manitoba maple or other maple in summer
Bugs crawling toward windows indoors on warm days in winter and early spring
A seed-bearing (female) Manitoba maple, also called a boxelder, on or near the property
Small stains on curtains, walls or fabric from their droppings
An unpleasant smell when one gets crushed

IDENTIFICATION

How to Identify Boxelder Bugs

Adult boxelder bugs are about 12 to 13 mm long, flat-backed and narrow. They are dark brownish black, with three red stripes on the area just behind the head and red edges along the front wings. The young, called nymphs, are smaller, wingless and bright red with a darker head. You will also hear them called box elder beetles or maple bugs. In the fall they share sunny walls with several other insects, and the ones people mix up most are below.

Boxelder bug vs western conifer seed bug: the seed bug is reddish brown to black, a little bigger at 13 to 19 mm, and has flat, leaf-shaped flares on its hind legs.
Boxelder bug vs brown marmorated stink bug: the stink bug is wider and marbled brown, with two white bands on each antenna and light and dark triangles along its edges.
Adult vs nymph: a bright red, wingless bug on a maple in summer is a young boxelder bug, not a different pest.

TYPES

Boxelder Bugs and Other Fall Invaders in Ontario

Boxelder bug
Boisea trivittata
Dark brownish black, about 12 to 13 mm, with three red stripes behind the head and red edges on the wings. Young are bright red and wingless.
Where found: On Manitoba maples, other maples and ash in summer; on sunny walls, siding and woodpiles in fall.
Western conifer seed bug
Leptoglossus occidentalis
Reddish brown to black, 13 to 19 mm, with a zigzag white line across the wings and flat, leaf-like flares on the hind legs.
Where found: Comes into homes in fall to spend the winter. It wasn't found in Ontario until about 1985.
Doesn't bite or sting.
Brown marmorated stink bug
Halyomorpha halys
14 to 17 mm and shield-shaped, marbled brown on top, with two white bands on each antenna and light and dark triangles along the edges.
Where found: Established in parts of southern Ontario. Adults move into homes and woodpiles in August and September and leave in May and June.
Doesn't bite and doesn't breed indoors.
Multicoloured Asian lady beetle
Harmonia axyridis
Varies a lot in colour, with no spots, a few or many, and always a white M-shaped mark just behind the head.
Where found: Picks sunny, south-facing walls in the fall and gets in through small gaps, sometimes in large numbers. First recorded in Canada in 1994.
Can nip if handled, and leaves a smelly, staining reddish fluid when disturbed.
Cluster flies
Pollenia spp.
To most people they look like house flies, but they're a little larger, dull grey with golden hairs on the thorax, and slow.
Where found: Get into attics, under siding and around windows in late summer and fall, then show up at windows on warm winter and early spring days.
They don't breed indoors: their larvae live in earthworms.
Cluster Fly Control

Mice and rats move indoors for the winter too: see mouse and rat control.

OUR APPROACH

How We Treat Boxelder Bugs

Step 1
Treat Before They Gather
The window is late August or early September, before boxelder bugs pile onto the walls and work their way inside. Late summer and early fall is when cooling weather sends them to sunny walls, and shortening days in August and September send stink bugs looking for shelter too. Once they're inside the wall voids they are out of reach, and indoor sprays don't do much.
Step 2
Focus on the Sunny Walls
They gather on the south- and west-facing walls that hold the afternoon heat, so the treatment goes there rather than evenly around the house. Sunlight breaks down exterior treatments quickly, which is one more reason the timing matters.
Step 3
Seal the Way In
Gaps around window and door frames, siding, soffits, vents, chimneys, light fixtures and utility pipes are how they get in. Sealing them and repairing torn screens is the longer-lasting fix, and it keeps out stink bugs, lady beetles and cluster flies at the same time.

BITES AND STINGS

Do Boxelder Bugs Bite?

Almost never. Boxelder bugs feed by sucking juices from seeds and leaves through a beak-like mouth, and Ohio State University says they aren't known to bite people or animals. Colorado State University says bites are rare. They don't sting. What they do is smell bad when crushed and leave small stains from their droppings. Of the other fall invaders, the Asian lady beetle is the one that may nip if you handle it; stink bugs and western conifer seed bugs don't bite.

RISKS AND DAMAGE

Are Boxelder Bugs Harmful to Your Home?

Boxelder bugs don't damage the house, clothing or food, and they don't breed indoors, so their numbers don't grow over the winter. Their feeding rarely affects the health of the tree. The trouble is the numbers and the mess: big clusters on siding, bugs at windows indoors, a bad smell when one is crushed, and stains on curtains, walls and fabric from their droppings. Dead bugs left in walls and attics can also draw carpet beetles.

Boxelder bugs are a nuisance, not a danger: a few on the walls is normal, while clusters every fall or bugs indoors all winter are worth treating the next late summer.

CAUSES

Why Boxelder Bugs Gather on Your House

Boxelder bugs spend the summer feeding on the seeds of Manitoba maples, the tree they're named after, and on other maples and ash. When the weather cools in late summer and early fall, the adults look for somewhere sheltered to spend the winter, and a warm, sunny wall with gaps in it is ideal. Bigger fall swarms tend to follow a hot, dry summer and a warm spring.

What Draws Them In

A seed-bearing (female) Manitoba maple on or near the property
Silver maples, other maples and ash nearby
South- and west-facing walls in full afternoon sun
Woodpiles, rock walls and debris against those walls
A hot, dry summer after a warm spring

How They Get In

Cracks around window and door frames
Gaps in siding and at soffits
Openings around vents, chimneys, light fixtures and utility pipes
Torn or missing window screens
Window air conditioners left in place into the fall

HABITS

Life Cycle and Habits

Habitat

Boxelder bugs live on and around Manitoba maples, also called boxelders, and also feed on other maples and ash. Through the summer they stay on the trees. In the fall they move to warm spots like south-facing walls, rocks, woodpiles and the south side of trees, then into cracks, wall voids and attics to spend the winter.

Diet

They suck the juices from the leaves, flowers and seeds of their host trees, and their favourite food is the seed of the female Manitoba maple. The ones that become active inside a house live only a few days to a week and don't reproduce there.

Life Cycle

Adults spend the winter in dry, sheltered places, often inside walls and attics. In late April or early May, about when the buds open on the trees, they leave their shelter, fly to the trees and lay eggs in bark crevices. The eggs hatch in about 10 to 19 days into bright red, wingless nymphs, which feed through the summer and become winged adults. There can be one or two generations a year, and new adults gather on buildings as the weather cools.

Seasonal Behaviour in Ontario

Late summer and early fall are when they gather on sunny walls, which is the window for treatment. Through the winter they stay mostly still inside walls and attics, but warm winter and spring days can bring some out into the living space, heading for windows. They don't breed indoors, and in spring the survivors leave for the trees again.

PREVENTION

How to Keep Boxelder Bugs Out

Seal cracks around window and door frames, siding, soffits and utility pipes before the end of summer.
Caulk around vents, chimneys and outdoor light fixtures.
Repair or replace torn window and door screens before fall.
Remove or cover window air conditioners before fall.
Clear debris and leaf piles away from the south and west sides of the house.
Cover firewood, and keep woodpiles away from the house walls.
Hose clusters off the walls when they first gather; they come back while the wall stays warm, so it's a stopgap.
If you're planting, choose another tree over a female Manitoba maple; they feed on its seeds.

How to Get Rid of Boxelder Bugs: DIY or a Professional?

A handful of boxelder bugs on the walls in fall is normal and doesn't need treatment. You can hose clusters off the siding or spray them with insecticidal soap from a garden centre, following the label, checking for a PCP number and testing it on a hidden spot first, since soap can stain cedar and some other siding, but more keep landing on the same sunny walls all fall. Indoors, vacuum them up and empty the vacuum outside right away, since bugs left in it can crawl back out. Large clusters every year, or bugs coming indoors all winter, are when an exterior treatment in late summer plus sealing the gaps is worth booking.

Boxelder Bugs Already on Your Walls or Inside?

Treating before they gather works best, but while they are still on the outside walls an exterior treatment can still cut down how many get in, so call as soon as clusters show up. Once they are spread through the wall voids, indoor sprays and bug bombs won't reach them. For the ones that wander into your rooms:

Vacuum them up instead of crushing them, which leaves a stain and a smell. Empty the vacuum outdoors right away.
Seal gaps around window and door trim, baseboards and ceiling fixtures so fewer of them find their way into the rooms.
Expect a few on warm, sunny days until spring. Next year, book the exterior treatment for late August or early September.

From the blog: Fall Pest Invaders: Why They Show Up Every Autumn

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Sting Out Pest Control helped me get rid of a pretty bad crawling insect problem in my office. They were friendly, easy to deal with, and explained everything clearly from the start. Instead of just spraying and leaving, they came up with a treatment plan that used different methods to get the problem under control. Over time, the infestation was completely gone. I now have them come by once a month for maintenance, and if anything small comes up, they take care of it right away before it becomes a bigger issue. It's been a great experience, and I have peace of mind knowing my office is protected. I would definitely recommend Sting Out Pest Control to anyone needing a reliable pest control company.

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COMMON QUESTIONS

Boxelder Bug Control: Questions We Get

When should boxelder bugs be treated?

Late August to early September, before they gather on sunny walls and well before they move indoors. That is when cooling weather starts sending them to the walls. Once they are spread through the wall voids they are out of reach of indoor treatment, and they will keep turning up on warm days through winter and spring. With this pest, timing matters more than the product.

Why are boxelder bugs in my house in winter?

They got into the wall voids and attic in the fall and spend the winter there, mostly inactive. A warm, sunny day wakes some of them, and they wander toward the light at windows. They don't breed indoors, so their numbers won't grow over the winter, and the ones that become active inside only live a few days to a week.

Why do boxelder bugs keep coming back every year?

Whatever drew them last year is still there: sunny south- or west-facing walls, Manitoba maples nearby, and unsealed gaps around windows, siding and soffits. Fall swarms are bigger after a hot, dry summer and a warm spring. Sealing the gaps cuts how many get in, and treating the walls each late summer, before they gather, keeps the numbers down.

Will cutting down the boxelder tree get rid of them?

It can lower the numbers if it's a female tree, since the seeds are their main food, but it rarely ends the problem. They also feed on the seeds of other maples, and trees on neighbouring lots are outside your control. Sealing and treating the house does more than removing a tree. If you're replacing it, a male boxelder or a different species avoids the seeds they feed on.

How do I get rid of stink bugs in my house?

Vacuum them up. Ontario's agriculture ministry says insecticides aren't recommended for brown marmorated stink bugs indoors, and that keeping them out is the most effective approach: seal cracks, repair screens and remove or cover window air conditioners before fall. They move in when the days shorten in August and September, don't bite and don't breed inside, and leave again in May and June.

Are Asian lady beetles the same as ladybugs?

They're a kind of lady beetle, but not one of the native species. The multicoloured Asian lady beetle was first recorded in Canada in 1994, and unlike native lady beetles it can't survive below about -5°C, so it moves indoors for winter. Look for the white M-shaped mark behind the head. They can nip if handled and leave a smelly, staining fluid, so vacuum them and empty the bag right away.

How much does boxelder bug control cost?

We quote each home rather than publish a set price. The cost depends on how many sunny south- and west-facing walls need the late-summer treatment, and how many gaps around windows, doors, siding, soffits and vents need sealing. Call (905) 739-7888 or send the quote form; the quote is free, and there's no binding contract.

Sources

Last updated October 20, 2026

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Boxelder Bug Control Across Toronto, Oakville & the GTA

We treat boxelder bugs in homes and businesses throughout Toronto and Southern Ontario.

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