Carpenter Bee Control: Protect Your Wood Without Wiping Out a Pollinator

Big black bees are hovering around the deck, and there is a perfectly round hole in the underside of a rail with sawdust beneath it. Those are carpenter bees. They are native pollinators and rarely sting, but years of nesting in the same boards can weaken wood and let in rot. This guide helps you confirm what you have, decide how much the damage matters, and protect the wood with paint, plugs and well-timed treatment.

How to identify carpenter bees

Carpenter bees look a lot like bumble bees. Check the abdomen and watch where they go.

In the eastern US, the common species is the eastern carpenter bee. Males have yellow or white markings on the face and hover near nests, darting at other insects and at people who move quickly. They look aggressive, but males have no stinger. Females have all-black faces and can sting, though they rarely do unless you handle them or press against one.

If the insect is smooth and banded yellow and black with a thin waist, it is a wasp. See our guide to wasps, hornets and yellowjackets instead.

Signs of carpenter bees

• Round holes about 1/2 inch across, roughly the width of your little finger, usually on the underside or edge of a board.
• Coarse sawdust piled below the hole.
• Yellow-brown stains below the openings from the bees’ waste, which often turn dark with mold.
• Bees hovering around eaves, decks and fences in spring.
• Woodpecker damage around the holes. Woodpeckers tear into the wood to reach the larvae inside.
• Faint chewing sounds inside the wood.

How carpenter bees damage wood

Carpenter bees do not eat wood. A female chews a round entrance hole, usually across the grain, then turns at a right angle after about an inch and tunnels along the grain. She builds a row of about five to ten cells, stocks each with pollen and nectar, lays an egg in each and seals them off. Tunnels often run 6 to 12 inches.

Adults spend the winter inside the tunnels. They come out in spring to mate and nest, and the new generation emerges in late summer, feeds on flowers and then returns to the wood for the winter.

One bee does very little harm. The trouble comes from reuse. Bees enlarge old tunnels and add new branches year after year, and over time that can weaken boards enough to need replacing. The holes also let moisture in, which speeds rot, and woodpeckers tear up the wood further while chasing the larvae.

They favor bare, weathered softwood such as cedar, redwood, cypress, pine and fir, especially boards more than 2 inches thick. Common targets include eaves, fascia boards, rafters, siding, shake roofs, decks, railings, doors, window sills and outdoor furniture. Painted and pressure-treated wood is much less likely to be attacked, and vinyl or aluminum siding keeps them out entirely.

Carpenter bees as pollinators

Carpenter bees are native bees that feed on nectar and pollen, and extension specialists describe them as useful pollinators. They are not aggressive. A few holes in a fence post at the back of the yard may not be worth treating. Focus your effort on wood that matters, such as fascia, siding, decks and anything structural.

If you do treat, treat only the holes in wood you care about, and time the work so you kill as few bees as possible.

How to get rid of carpenter bees, step by step

1. Confirm it is a carpenter bee. Check for the shiny abdomen and a round hole in wood.
2. Decide whether the wood is worth protecting. Old, unpainted boards that are already riddled with tunnels may be better replaced with painted or less attractive material.
3. Paint exposed wood. This is the most lasting protection. Use an oil-based or polyurethane paint, and fill cracks and nail holes with caulk or putty before painting. Stains and preservatives repel bees far less reliably than paint. Check painted surfaces regularly and touch up spots where the paint has weathered.
4. Close up outbuildings in spring. Bees search for nest sites in spring, and that searching usually tapers off by late spring. Keep garage and shed doors shut during that window.
5. Consider traps. Wooden boxes with 1/2-inch holes and a bottle hanging below can catch bees looking for nest sites when hung under eaves and overhangs at the corners of a building in early spring. Use them alongside paint and plugging, not in place of them.
6. Treat active holes if needed. See the next section.
7. Plug the holes at the right time. After treatment, or once the tunnels are empty, plug each hole and paint over it.

Treating and plugging holes

• Treat early. The best time is spring, when bees first appear and before tunnels are fully built. Penn State Extension also suggests follow-up treatments in mid-summer and early fall.
• Use the right form. Insecticide dusts puffed into the hole coat the tunnel walls and last longest. Products labeled for carpenter bees often contain pyrethroids such as bifenthrin, cyfluthrin, deltamethrin or lambda-cyhalothrin. Apply lightly. Heavy use can push bees to start new holes nearby. Read and follow the label.
• Treat at dusk or at night. Bees are inside and less active. A flashlight covered with red cellophane helps, since bees do not see red light. Wear gloves, eye protection, long sleeves and a dust mask.
• Leave holes open for a few days to a week. Bees going in and out spread the dust through the tunnel. If you plug a hole right after treating, or plug an untreated active hole, bees may chew through the plug and come back out.
• Then plug. Use a wooden dowel coated with carpenter’s glue, wood putty, or steel wool or copper gauze topped with putty. Then paint or varnish over it. Plugging deters reuse and keeps out moisture.
• Late summer and fall are good times to plug and repaint empty holes, after the new generation has emerged.

Spraying the surface of boards gives only short-term protection, about 3 to 4 weeks, and needs repeating. Borate wood treatments generally do not work against carpenter bees. Before you buy any product, read our guide to using pesticides safely, and check the seasonal pest calendar to plan spring prevention.

Do not treat from a ladder while bees are active. A startled female can sting, and swatting at bees on a ladder is a fall risk. Leave high eaves and soffits to a professional.

When to call a professional

Most carpenter bee problems on decks, fences and furniture are DIY jobs: paint, plug and, if needed, dust a few holes.

Call a licensed pest control company if:

• The holes are in eaves, soffits, fascia or anywhere that needs a tall ladder.
• You have dozens of holes across siding, a shake roof or deck framing.
• Wood looks soft or rotted around the holes, or woodpeckers have torn into it. You may also need a carpenter to replace damaged boards.
• Someone in the home is allergic to stings.

A pro visit usually means treating each active hole with dust, sometimes treating the most vulnerable surfaces, and returning to check results. Ask:

• Which product will you use, and will you treat only the holes or spray surfaces too?
• When will you come back, and who plugs the holes afterward?
• What would you recommend to keep them from coming back, such as painting or replacing boards?

Our guide to choosing a pest control company has more questions, and pest control costs explains what affects the price.

Carpenter bee questions

Will they come back to the same holes? Yes. Females reuse and enlarge old tunnels, which is why unplugged holes lead to more damage each year.

Are carpenter bees as bad as termites? No. Their damage is seldom as severe as termite damage, but years of reuse can still weaken boards. If you find soft, damaged wood with no round holes, check our signs of termites.

Does stain keep them away? Not reliably. Stain offers some repellency compared with bare wood, but paint works much better.