BuzzSkito Mosquito & Tick Control Specialists · Published July 30, 2026
What a Carpenter Bee Is Doing to Your House
A female carpenter bee does not eat wood. She excavates it, and understanding that changes what you should do about it. She chews a nearly perfect round entrance hole, roughly a centimetre and a bit across, into a piece of bare softwood; then she turns about ninety degrees and tunnels along the grain, hollowing out a gallery in which she builds a row of brood cells, each provisioned with pollen and sealed. The wood she removes is discarded, which is why a fresh hole has a small heap of coarse sawdust on the deck beneath it, and often a streak of yellowish staining running down the boards below the entrance.
One hole in one railing is not a structural event. The reason carpenter bees earn a page is reuse. Galleries are re-occupied and extended year after year by successive generations, so a fascia board that had one entrance in it three summers ago can now have a branching tunnel system inside it and half a dozen entrances along its length. Water gets into a board like that. And in a member that is carrying load — a rafter tail, a header, a deck beam — the accumulated hollowing is worth having somebody look at properly.
The second reason is the bird. Woodpeckers detect larvae inside the galleries and will chisel the board open along the tunnel to reach them, turning a tidy one-centimetre hole into a long ragged trench. In many Canadian yards that woodpecker damage is far more expensive than anything the bees did directly. If you are looking at a shredded fascia and blaming the bird, the bird is a symptom.
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The Order of Operations, and Why Getting It Wrong Costs You a Season
Almost every failed carpenter bee job is a sequencing error rather than a product error. Here is the sequence that works.
1. Treat the open gallery. Puff a registered insect dust into the entrance hole with a bulb duster — a small squeeze, not a packed hole — and then leave the hole open for several days. This is the counter-intuitive part. The point is that returning females and emerging adults walk through the material and carry it into the tunnel, which reaches the parts of the gallery your duster tip never will. Sealing immediately after treating throws away most of the benefit.
2. Plug once activity has stopped. The safest window is autumn, after the season is over. Drive a snug wooden dowel into the entrance with exterior glue, or pack it with an exterior-grade wood filler, then seal it flush and sand it. Plugging an active mid-season gallery is the classic mistake: the occupant tunnels along the grain and can simply chew around your plug, giving you a fresh hole a few centimetres away, and sealing developing larvae into a board is exactly what brings the woodpecker.
3. Paint the wood. This is the step people skip and it is the one that decides next May. Carpenter bees strongly prefer bare, unfinished, weathered softwood. A sound film of exterior paint is a real deterrent; stain and clear sealer soak into the wood rather than forming a film and are much weaker. Painting the whole elevation — not just the patch you filled — is what stops a new female choosing the board next to the repaired one.
If you would rather use no product at all, that is a legitimate plan: skip step one, wait for autumn, and do steps two and three. You will lose that season’s brood to nothing, but the durable fix is the carpentry and the paint regardless.
What You Can Legally Buy in Canada — and the American Advice Problem
Search this topic in English and nearly every result is written for a US reader, and nearly every one of them names a deltamethrin dust. That is genuinely the standard American recommendation, and it is not a Canadian one, because a pesticide registered in the United States is not thereby legal to sell or use in Canada.
The rule here is simple and it is worth applying before you add anything to a cart. Any product sold or used as a pesticide in Canada must be registered with Health Canada’s Pest Management Regulatory Agency and carry a PCP registration number on the Canadian label. That label is legally binding: the pests it lists and the sites it names are the uses you may legally make of it. So there are two checks, not one — is there a PCP number, and does the label actually cover this pest and this site?
On the domestic Canadian shelf, the dust a homeowner can genuinely buy is PMRA-registered insecticidal diatomaceous earth: Safer’s Diatomaceous Earth is the most widely stocked, with Knock Down and Doktor Doom Be Green as registered alternatives. It kills mechanically, by abrading and absorbing the waxy layer that holds an insect’s moisture in, which means nothing develops resistance to it and the powder does not expire. A carpenter bee gallery in weathered fascia is a dry, enclosed space, which happens to be the condition DE needs — its normal weakness, going inert when damp, matters much less inside a tunnel than it does on an exposed surface. Buy a bulb duster with it, wear a dust mask while applying, and read the label’s pest list and use sites before you start, because the mechanism being right does not make every application a legal one. Our Canadian diatomaceous earth buyer’s guide covers grades, the food-grade and pool-grade distinction, and application technique in full.
Do not buy a US-only formula from a marketplace seller shipping north. It is an unregistered pesticide in Canada, it carries a US-only label that gives you no Canadian directions to rely on, and it can be stopped at the border.
Carpenter Bee Traps: What They Do, and What They Cannot Do
Carpenter bee traps deserve better than the blanket scepticism most novelty pest traps earn, because unlike an “earwig trap” or an ultrasonic plug-in, this one is engineered around a behaviour that genuinely exists. The trap is a small wooden box with entrance holes bored at approximately the diameter and upward angle of a real gallery. A prospecting female investigates the hole, moves inward and downward toward the light coming from a clear jar fixed below, and cannot find the small dark entrance again to get out.
Where they earn their place: hung early, at spring emergence, high up at a roof peak, a gable end, or a corner near where you saw activity last year, in the sun rather than in shade. Several along one elevation beat one in the middle of a wall. They intercept females that are shopping for a nest site, which is exactly the moment you want to intervene.
Where they disappoint, and why the honest verdict is “supplement”: a trap does nothing about the galleries already in your fascia. A bee with an established, provisioned tunnel has no reason to investigate a box hanging two metres away. Nobody clears an infested board with traps, and a household that hangs six traps and does no filling or painting will be doing the same thing next May. Hang them alongside the treat-plug-paint work, not instead of it.
One more consideration that belongs on an honest page: carpenter bees are native pollinators. They visit a wide range of flowers and can buzz-pollinate, which some plants rely on. Hanging traps is a lethal control, and it is worth aiming it at the wood you actually need to protect rather than blanketing a property.
Prevention Is a Painting Job
If you take one thing from this page, take this: the durable answer to carpenter bees is not a pesticide, it is a coat of exterior paint, and the trade you may actually need is a painter.
- Paint the vulnerable softwood. Fascia, soffit boards, railings, deck framing that shows, pergola beams, shed trim, playsets, and outdoor furniture. A sound film is the deterrent. Bare weathered cedar and pine is what they are looking for.
- Understand the paint-versus-stain gap. Stains and clear sealers penetrate rather than forming a surface film, and are correspondingly weaker here. If your deck is stained and being bored, that is not a failure of the stain — it is the wrong tool for this particular job.
- Cap what keeps getting hit. Aluminium or vinyl-clad trim over a repeatedly attacked fascia removes the surface from the equation entirely, and it is a common answer where woodpeckers have already opened a board.
- Close the gaps while you are up there. Quarter-inch galvanised hardware cloth over open soffit and gable-vent gaps stops birds and wasps taking up residence in the same roof space, and it is the same material and the same ladder trip.
- Replace the wood that is past saving. A fascia board that is more tunnel than timber is not a filling job.
- Maintain it. Bare weathered patches where paint has failed are exactly where next year’s female will start.
What Not to Do
- Do not pour WD-40, gasoline, diesel, or any other non-pesticide into the holes. It is a fire hazard on a wooden structure, it is using a product as a pesticide in a way no label authorises, and it does not solve the gallery.
- Do not foam or caulk an active gallery and walk away. Either they chew around it or you have sealed larvae into a board and given a woodpecker a reason to open it.
- Do not buy an ultrasonic repeller. There is no credible evidence base for the category across household pests — see our ultrasonic pest repeller review.
- Do not buy a bug zapper for this. Carpenter bees are day-flying and are not drawn to UV light; a zapper kills large numbers of harmless moths and beetles instead. Our bug zapper review for Canada covers what they actually catch.
- Do not treat bumblebees by mistake. Furry abdomen, nests in the ground, bores nothing — and some Canadian species are assessed as at risk. If it is not making holes in your wood, it is not the animal on this page.
- Do not work at height without proper footing. The most dangerous part of this entire project is the ladder, not the bee.
When to Call Someone — and Which Trade
BuzzSkito treats mosquitoes and ticks and does not sell carpenter bee service, so there is nothing here to protect: for most southern Ontario homeowners this is a weekend of dusting, filling, and painting, and a recurring spray programme that never fills a hole or paints a board is a subscription rather than a fix.
Three situations justify paying someone, and in two of them the right trade is not an exterminator. Galleries in structural members — rafters, headers, beams, deck framing — want a carpenter or a building inspector to judge whether the wood is still sound before anything is filled and hidden. Extensive woodpecker damage that has opened a fascia or soffit run wants proper repair and capping, which is again carpentry. And any work at height on a two-storey fascia is worth paying for on safety grounds alone. For sanity-checking a quote from a pest company if you do get one, our Canadian pest control cost guide gives you a baseline — and be sceptical of any quote that is a spray schedule with no mention of filling or painting the wood.
Frequently Asked Questions
How do I get rid of carpenter bees?+
In a specific order, and the order is the whole trick. First treat the open gallery — puff a registered insect dust into the entrance hole with a bulb duster and then leave the hole open for several days, so returning females walk through it and carry it into the tunnel. Second, plug the hole once activity has stopped, ideally in autumn: drive a snug wooden dowel or exterior wood filler into the entrance and seal it flush. Third, paint the surface. If you skip straight to plugging an active gallery you will usually get a fresh hole a few centimetres away, because the bee inside tunnels with the grain and can simply chew around your plug. And if you skip the paint, next spring a new female will find the same bare, weathered board that attracted the first one.
Are carpenter bees even found in Canada?+
Yes, but not everywhere, and this is worth checking before you buy anything. The eastern carpenter bee is a southern species whose Canadian range is limited and concentrated in southern Ontario. Across most of the Prairies, the North, and much of Atlantic Canada, a large black-and-yellow bee hovering around a deck is far more likely to be a bumblebee — which does not bore into wood at all, nests in the ground or in existing cavities, and is a valuable pollinator you should leave completely alone. The decisive check takes two seconds: look at the top of the abdomen. Carpenter bees have a shiny, hairless, almost polished black abdomen. Bumblebees are densely furry all over.
Do carpenter bees sting?+
The one dive-bombing your head almost certainly cannot. That aggressive hovering, territorial behaviour is the male, and male bees have no stinger at all — the sting is a modified egg-laying structure, so only females have one. Males are all display: they hover, they chase other insects and people who walk under their patch of fascia, and they are physically incapable of stinging. Females can sting and are notably reluctant to, generally only doing so if handled or trapped against skin. In practice carpenter bees are a property problem rather than a safety problem, which is a genuinely different situation from a wasp or hornet nest by a doorway. If you can tell males from females, the white or pale patch on the face is the male.
Do carpenter bees actually eat wood?+
No — they excavate it, which is why the damage looks so different from termite or carpenter ant work. A female chews a nearly round entrance hole roughly a centimetre and a bit across, then turns about ninety degrees and tunnels along the grain to create a gallery where she builds a row of cells and provisions each with pollen. The wood she removes is discarded as coarse sawdust, which is why you find a small pile of it on the deck below a fresh hole, often with yellowish staining streaked down the boards beneath the entrance. The reason it becomes serious is reuse: galleries are re-occupied and extended year after year by successive generations, so a fascia board with one hole in it can quietly become a honeycombed board over several seasons.
What wood do carpenter bees attack, and what stops them?+
They strongly prefer bare, unfinished, weathered softwood — cedar, pine, fir and similar — which in a Canadian yard means deck railings and joists, fascia and soffit boards, pergolas, fence posts, shed trim, playsets, and unpainted outdoor furniture. What genuinely deters them is a sound coat of exterior paint on the surface. Stain and clear sealers are much weaker deterrents because they soak in rather than forming a film, and bare wood is an open invitation. That single fact reorganises the whole job: the durable fix for carpenter bees is a painting task, not a spraying task. Hardwoods and properly painted surfaces are far less attractive, and aluminium or vinyl-capped trim is not attackable at all.
Why are woodpeckers tearing up my fascia?+
Because there are carpenter bee larvae inside it, and this is very often the largest part of the damage bill. A woodpecker can hear or detect the larvae in the gallery and will chisel the board open along the tunnel to get at them, converting a neat one-centimetre hole into a long ragged trench. If you are seeing woodpecker damage on a fascia or a soffit, treat it as a carpenter bee diagnosis rather than a bird problem — deterring the bird while leaving the larvae in place solves nothing, and the bird is only there because of the food. Deal with the galleries, plug them, paint the board, and the woodpecker loses interest. Capping the repaired area with aluminium trim is a durable answer where the same board keeps getting opened up.
What can I legally use on carpenter bees in Canada?+
Whatever you use has to be registered by Health Canada’s Pest Management Regulatory Agency, carry a PCP registration number on the Canadian label, and list on that label both the pest and the site you intend to treat. This matters more than usual here because the product every American guide recommends for carpenter bees is a deltamethrin dust, and a US registration does not make a pesticide legal to sell or use in Canada. Before ordering anything from a marketplace listing, check for a Canadian PCP number and confirm the item ships from within Canada. On the domestic shelf here, PMRA-registered insecticidal diatomaceous earth — Safer’s Diatomaceous Earth is the most widely stocked, with Knock Down and Doktor Doom Be Green as registered alternatives — is the desiccant dust a homeowner can actually buy, applied with a bulb duster. Read that label’s pest list and use sites rather than assuming the mechanism makes the application legal.
Do carpenter bee traps work?+
They work on a real behaviour, which puts them well ahead of most novelty pest products, and they are still a supplement rather than a cure. The design mimics what a female is looking for: a wooden box with angled entrance holes bored at roughly the diameter and angle of a natural gallery, and a clear jar below. A bee enters the hole, moves down toward the light in the jar, and cannot find its way back out. They catch best when hung early, at emergence in spring, high up at a roof peak or corner near known activity and in the sun. What they will not do is clear an established gallery system in a fascia board — the bees already tunnelling in your wood have somewhere better to be. Hang traps as a supplement to treating, plugging and painting, never as a replacement for it.
Can I just plug the holes?+
Timing decides whether that works or backfires. Plugging an active gallery in mid-season generally produces a fresh hole a short distance away, because the occupant tunnels along the grain and can chew around a plug — and sealing developing larvae inside a board is exactly the situation that draws a woodpecker to open it up for you. The reliable sequence is to treat the open hole first, leave it open for a few days so returning bees pick the material up, and then plug it. If you would rather not use any product at all, wait until autumn when the season’s activity has finished, then plug and paint. Use a snug wooden dowel driven in with glue, or an exterior-grade wood filler, seal it flush, and then paint over the repair — the paint is what stops next spring’s female choosing the same board.
Should I kill carpenter bees at all?+
Sometimes the honest answer is no, and it is worth thinking about for thirty seconds before you buy a trap. Carpenter bees are native pollinators — they visit a wide range of flowers and can buzz-pollinate, which some plants depend on. If the holes are in an old fence post, the back of a shed, a woodpile, or a pergola you do not particularly care about, leaving them alone is a legitimate choice and costs you nothing. The case for intervening is structural: galleries in fascia, soffit, deck framing, railings, or any load-carrying member will be extended year on year, will attract woodpeckers, and will let water into the wood. Treat the wood you need to protect, paint it, and consider leaving the ones in the far fence line to get on with it.
When do carpenter bees show up in Ontario?+
They overwinter as adults inside old galleries and emerge in spring as the weather warms — in southern Ontario, generally from around May, with the conspicuous hovering, chasing and boring activity running through late spring and early summer. That is when you see the males patrolling and the fresh sawdust appearing. New adults emerge later in the summer, feed, and then return to tunnels to overwinter, which is why activity around the same fascia board tapers off and then resumes. The practical calendar: hang traps and inspect for fresh holes in spring at emergence; treat galleries during the active season if you are going to; and do the plugging and painting in autumn, when activity has finished and the repair will not be chewed around.
Do I need a pest control company for carpenter bees?+
Usually the trade you actually need is a painter or a carpenter, not an exterminator, and saying so saves people a recurring bill. The durable fix is filling the galleries and putting a sound coat of exterior paint on the wood, and no spray programme substitutes for that. Bring in a professional in three situations: galleries in structural members such as rafters, headers, beams or deck framing, where somebody needs to assess whether the wood is still sound; extensive woodpecker damage that has opened up a fascia or soffit run and needs proper repair and capping; and any job that means working at height on a two-storey fascia, which is genuinely the most dangerous part of this whole project and not worth a fall. Be sceptical of a quote that is only a spray schedule and never mentions filling or painting the wood.
Related Guides
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- Best Wasp Trap in Canada — When a Trap Helps and When It Does Not
- Carpenter Ants in Canada — The Other Insect Hollowing Out Your Wood
- Diatomaceous Earth in Canada — Which Brands Are PMRA-Registered
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- Do Ultrasonic Pest Repellers Work? The Honest Answer
- Pest Control Cost Canada — What Professionals Charge
