Carpenter bees: the round holes in your deck rail, eaves and fascia
Published Updated
By John Stopka, Co-Founder & CEO · Reviewed by John Stopka
Clean, round holes about the width of your little finger in a deck rail, eave or fascia board, with coarse sawdust below them, are carpenter bee work. They do not eat the wood — they tunnel into it to raise their young, and the damage compounds because the same galleries are reused and enlarged year after year. They are pollinators too, so what needs dealing with is the wood.
What are carpenter bees actually doing to the wood?
Excavating it, not eating it. They are named for boring into wood to rear their young [1], and University of Illinois Extension is plain about it: they do not feed on the wood, they are digging out a nest [2].
The entrance is the giveaway. University of Kentucky entomologists describe it as "perfectly round and about the diameter of your little finger" [1]; Illinois Extension puts it at about half an inch across [2]. Coarse sawdust often collects below the opening, and tunnelling sounds are sometimes heard inside the wood [1].
Behind that entrance, the bee turns a right angle and tunnels parallel to the surface [1]. The hole is the doorway to a gallery you cannot see.
How do I tell a carpenter bee from a bumble bee?
Look at the abdomen. Shiny versus fuzzy is the tell worth remembering.
Carpenter bees "typically have a shiny, hairless abdomen", while bumble bees usually have a hairy one with black and yellow stripes [1]. Illinois Extension describes the same split and puts both at roughly three-quarters of an inch, which is why they get mixed up [2].
Nesting differs too: bumble bees use an existing cavity, often underground, while carpenter bees tunnel into wood to lay their eggs [1]. So if it is hovering at a hole in your fascia board and its back end shines, it is a carpenter bee.
Which wood do carpenter bees go for?
Bare, weathered softwood. UK Entomology says they "prefer unpainted, weathered wood, especially softer varieties such as redwood, cedar, cypress and pine", and that "painted or pressure-treated wood is much less susceptible to attack" [1]. Illinois Extension names the same soft woods and adds fir [2].
The places that get hit are the ones you would guess: eaves, rafters, fascia boards, siding, wooden shake roofs, decks and outdoor furniture [1].
Finish matters more than species — carpenter bees "usually will not tunnel into painted wood" [1]. The other thing that draws them is history: old tunnels are an invitation, which is the next problem.
Will a carpenter bee sting me?
Worth being precise, because the bee making all the fuss is the one that cannot.
The male is the conspicuous one: he hovers in front of people near nest sites [1], and Illinois Extension notes males patrol territories, seeing off other bees, pets and people [2]. But males "lack the ability to sting" [1] — as Illinois Extension puts it, "it's all a show" [2].
Females can sting, and seldom do. A female "can inflict a painful sting but will seldom do so -- unless they are handled or bothered by people" [1]; Illinois Extension agrees they are not aggressive [2]. Up close, males have a whitish spot on the face; females' faces are all black [2].
If anyone is stung and has any reaction, contact a healthcare provider.
Why does the damage get worse every year?
Because the galleries are reused rather than abandoned.
Females "excavate new tunnels in wood for egg laying, or enlarge and reuse old ones", and "significant damage can occur when the same pieces of wood are infested year after year" [1]. Adults overwinter individually, often in brood tunnels built in an earlier season [1].
Illinois Extension sets out where that tips over: tunnels used for several years, or several nests in one piece of wood over several years, can compromise that wood's structural integrity so it has to be replaced [2].
The holes also "facilitate moisture intrusion, rot and decay" [1] — a rail drilled for five springs is not only marked, it has been ventilated. And the bees defecate before entering their tunnels, staining the surfaces below [2].
Why do woodpeckers show up after carpenter bees?
Because the larvae are food. Illinois Extension is direct about it: "Woodpeckers may also damage wood in search of the bee larvae." [2]
That is how a fascia board goes from a few neat round holes to a torn-open mess. The bee makes a half-inch entrance; a woodpecker opens the gallery along its length — and that second round of damage is usually the one people notice from the driveway.
Should I just leave carpenter bees alone?
Sometimes. Illinois Extension calls carpenter bees beneficial insects to have around, pollinating a range of flowers, particularly large open-faced ones like sunflowers, coneflowers and asters [2]. So the reason to act is a specific piece of structural wood being tunnelled and re-tunnelled — not bees in the garden.
How does Liberty handle carpenter bees?
Carpenter bees are not part of Liberty's plans, so carpenter bee treatment starts with a free inspection.
A local Service Advisor looks at how many holes and bees there are, where they are drilling, and what is drawing them — typically bare, unpainted or weathered wood on eaves, decks and railings.
A Service Specialist then treats the active holes and the wood around them, and points out which wood to paint or stain. Follow-up visits check for new holes.
General pest control plans cover everyday pests like ants and spiders. Carpenter bees sit outside that, and the work is quoted after the inspection.
When to call a professional
Call when the round holes are in structural wood — fascia, rafters, deck framing — rather than in a piece of outdoor furniture you could replace. Call when the same boards are drilled again each spring, and when woodpeckers have started opening the galleries.
UK Entomology notes the best time to deal with carpenter bees is before the tunnels are fully constructed [1], which means spring, as the overwintered adults emerge [1] [2]. An inspection settles how far the tunnelling has gone and which wood is at risk.
Common questions
Do carpenter bees eat wood?
No. They tunnel into wood to make nest galleries and push the sawdust out of the entrance hole; they do not feed on it [2]. That is why they are described as seldom as destructive as termites, though still able to do cosmetic and structural damage [1].
Do carpenter bees sting?
Males cannot sting at all, which matters because the hovering, territorial bee that comes at you near a nest hole is usually a male [1] [2]. Females can inflict a painful sting, but seldom do so unless handled or bothered [1]. If anyone is stung and has a reaction, contact a healthcare provider.
When are carpenter bees most active?
Spring. Adults overwinter individually inside old tunnels, then emerge and mate, and the females bore into wood to lay eggs [1]. Illinois Extension puts emergence and mating in April and May, with new adults appearing in late summer before returning to tunnels for winter [2].
Are carpenter bees covered by a Liberty pest control plan?
No. Carpenter bees are not a plan pest at Liberty. Plans cover everyday pests like ants and spiders, and carpenter bee work starts with a free inspection instead.
Sources
- University of Kentucky Entomology. Michael F. Potter. "Carpenter Bees" (ENTFACT-611). https://entomology.mgcafe.uky.edu/ef611 (opens in a new tab)
- University of Illinois Extension. Ken Johnson. "Carpenter bees: Destroyers of wood or beneficial pollinators?" (Good Growing). https://extension.illinois.edu/blogs/good-growing/2023-05-05-carpenter-bees-destroyers-wood-or-beneficial-pollinators (opens in a new tab)