Carpenter Bees

Three picks, depending on where you are with the bees. The plug kit has tapered wood plugs in three sizes for holes the bees have left. The citrus and almond oil spray is meant to discourage boring in decks and fences, the listing says. The catch-and-release trap has a latch so a bee can be let go.

What It Is

University of Maryland Extension: Eastern carpenter bees are large bees approximately 0.75-1 inch long. The thorax or midsection is covered with yellow fuzz. The abdomen, or the hind section, is shiny and black. UC IPM gives a closely matching description for the wider genus: Carpenter bees are large and robust insects resembling bumblebees.

• Sex differences. University of Maryland Extension states females have a black face and a dense brush of black hairs on their hind legs, while males have yellow faces. Ohio State University Extension adds that the female has an entirely black head, whereas the male has yellow or white markings.
• Diet. University of Maryland Extension: Carpenter bees do not eat wood, they eat flower nectar and pollen. The holes they bore into wood are nests for their young.

Carpenter Bee vs. Bumblebee

University of Maryland Extension: Carpenter bees are often mistaken for bumblebees, which are similar in size. However, the bumble bee’s entire body is covered with hairs, and females have yellow patches of hair on the top of the abdomen. Bumblebees are social, living together in an underground nest.

Ohio State University Extension gives a second, independent test: Carpenter bees resemble bumble bees as they are similar in size except for their head, with the bumble bee’s head being much narrower than the width of the thorax. The same source states Bumble bees are social insects that live in colonies with nests typically located in the ground.

Alabama Cooperative Extension adds a behavioral test neither of the above gives: carpenter bees fly in a more erratic way, chasing one another, while bumble bees fly leisurely together, and carpenter bees are solitary and less defensive of their nest sites while bumble bees are social and extremely defensive when their nest site is disturbed.

Carpenter Bee vs. Honeybee

None of the five sources read for this page treats honeybee confusion as a major identification problem — the size difference is large enough that the sources spend their identification space on the bumblebee comparison instead. The honeybee is smaller than a carpenter bee, lives in a large social colony rather than a solitary wood tunnel, and (per the honeybee sting material on our social wasps page) leaves a barbed stinger in the skin, which no source here attributes to the carpenter bee.

Nesting and Boring Behavior

University of Maryland Extension: The female chews a perfectly circular hole approximately half an inch in diameter. This entry hole extends 1-2 inches into the wood and then turns at a right angle to follow the grain of the wood.

On how far a gallery runs, the sources give different figures, and each is reported as its own source states it. University of Maryland Extension gives 6-12 inches for a new gallery, with nests reused over years occasionally measuring up to 10 feet. Ohio State University Extension gives 4 to 6 inches for a new gallery, excavated at about 1 inch every six days, with multi-year reuse extending it as far as 10 feet. Alabama Cooperative Extension gives 4 to 6 inches typically, up to 2 feet with repeated reuse. No figure is corrected against another here.

Ohio State University Extension states the gallery is more than empty space to the bees themselves: Carpenter bee galleries are a critical resource, since the bees spend much of their time inside a gallery and they require its protective conditions to survive the winter. The same source notes bees sealed inside a treated gallery typically will not chew their way back out.

On timing, University of Maryland Extension states nest-site searching happens in April or May; Ohio State University Extension and Alabama Cooperative Extension both place emergence and mating in early spring, with new adults emerging in late summer and overwintering together in the gallery until the following spring. There is one generation a year in northern states, per UC IPM, sometimes two further south.

The Damage

UC IPM: Carpenter bees build nests in wood, creating galleries that can weaken structures; however, they rarely cause severe damage. Alabama Cooperative Extension frames the same fact from the other direction: Carpenter bees are good pollinators and naturally nest in dead trees and woodpiles, but they have taken up residence in close proximity to human habitation and cause extensive damages to wood structures, including homes, when they repeatedly colonize exposed wood and they are not controlled.

• Signs. University of Maryland Extension names sawdust piles below perfectly circular holes, large bees buzzing around the head, and fan-shaped yellow or moldy stains on the sides of a structure — the stains are the female’s sticky waste, which darkens with mold as it ages.
• Where they nest. Ohio State University Extension names fascia boards, roof eaves and gables, porch ceilings, decks, railings, siding, shingles and shutters, and states the inner surface of roof fascia boards is now a common site of attack, because exposed nests were the ones most easily targeted by management in the past.
• Secondary damage. University of Maryland Extension names moisture entering exposed wood and accelerating decay, mold growth on the bee’s waste, and woodpecker damage from birds feeding on the immature bees inside the gallery — Alabama Cooperative Extension makes the same point about woodpeckers tearing into galleries and worsening the damage to the point wood needs replacing.

Pollinator Status

This page states the position found in the sources plainly, because the scope of this page depends on it. No source read here describes a legal restriction, permit requirement, or protected-species status for carpenter bees anywhere in the United States. What the sources do describe, consistently and from five independent institutions, is a conservation caution against killing them without reason.

• Penn State Extension: Carpenter bees are important pollinators of many flowering plants found in our gardens, natural areas, and on farms. In fact, 15% of our agricultural crops are pollinated by native bees such as carpenter bees. The same source states directly: Killing individual bees or indiscriminate pesticide applications are unlikely to provide satisfactory results.
• UC IPM: Carpenter bees are generally considered beneficial insects because they help pollinate various crop and noncrop plants. Under most conditions their damage can be successfully managed using the preventive measures described above and insecticide use is not recommended.
• University of Maryland Extension frames the timing of any repair work around the same concern: The best times to treat and repair damaged wood and minimize the killing of these pollinators would be late summer (after the summer emergence and before hibernation) or early spring before nest building begins.

Not every source agrees on how far that caution should go, and both positions are reported rather than resolved into one. Ohio State University Extension names specific pyrethroid insecticides labeled for carpenter bee control and describes dust-formulation application in detail, without discouraging the practice. Alabama Cooperative Extension likewise describes insecticide formulations and application timing at length, while stating in the same breath that the goal of control is to deter nesting damage — not to eliminate all the bees in the yard — since they are important pollinators. UC IPM and Penn State Extension are more direct in recommending against insecticide use specifically. This page does not pick a side between them; it reports what each institution states.

What this page does do, given that range, is card only non-lethal products — a trap, a repellent, and repair materials — rather than an insecticide, further down this page.

Treatment and Repair

Ohio State University Extension describes the non-insecticidal barrier approach in full: A non-insecticidal management approach is to deny carpenter bees access to their galleries by sealing each entrance hole. Thoroughly plug the hole with plastic wood, steel wool, or copper gauze and seal it with wood putty or a wooden dowel affixed with wood glue. UC IPM gives a closely matching sequence — fill unoccupied holes with steel wool and caulk, wait until after bees have emerged before filling active tunnels, then paint or varnish the repaired surface.

Timing the repair matters for the same reason timing the repellent does. University of Maryland Extension’s guidance above places the work in late summer or early spring, specifically to avoid trapping active brood or provoking a female mid-nest. Alabama Cooperative Extension agrees early spring, before eggs are laid, is the best window.

Stings

Handling a bee, or reaching directly into an active hole, is the situation every source names as the one that provokes a sting.

Prevention

UC IPM: prevention is the main approach to managing carpenter bees, and susceptible exterior parts of a building should be constructed out of hardwoods where possible, since carpenter bees avoid most hardwoods and prefer softwoods. Ohio State University Extension names cedar, redwood, cypress, pine and fir specifically as woods the eastern species prefers.

• Paint, not stain. Ohio State University Extension states plainly that wood stains will not prevent damage from carpenter bees, while keeping exposed wood well painted with a polyurethane or oil-based paint deters attack. University of Maryland Extension agrees that painted surfaces are unattractive to nesting bees, and that nail holes and cracks should be filled with caulk or putty before painting.
• Non-wood alternatives. UC IPM and Ohio State University Extension both note that carpenter bees do not damage non-wood materials such as aluminum, asbestos, asphalt and vinyl siding, which can substitute for wood on vulnerable, exposed parts of a structure.
• Repellents. Alabama Cooperative Extension: The best time is before the female lays eggs in the tunnel. Products with essential oil components can repel carpenter bees from carving tunnels or abandoning the excavated nest. Penn State Extension names almond oil specifically, applied annually in spring, as an effective deterrent for those who prefer an unpainted, natural wood finish.

The products below are named because the sources on this page describe repelling and then plugging the gallery, and each listing states which of those two jobs it does.

When to Call a Professional

None of the five sources read for this page names a specific threshold for calling a professional the way some wildlife-exclusion sources do. What they describe instead is a job that grows with the number of galleries: Alabama Cooperative Extension notes it can be very challenging to reach many of the holes bees are using, and that a pest management professional brings the experience and equipment to make an effective and safe application. A single hole with an easily reached, paintable surface is squarely within the DIY prevention and repair steps above; a fascia board or roofline riddled with multiple active galleries, or a structure where reaching the holes safely requires height equipment, is where the sources point toward hiring help.

Questions

Sources

Every factual claim above names the source it rests on, in the sentence that makes it or in the text immediately adjacent to it, and every source named is listed below. Framing, ordering and emphasis are our own judgment and are not a finding of any source. Where sources give different figures or take different positions on insecticide use, all are reported and attributed rather than resolved into one answer.