How do I get rid of carpenter bees?

Treat the hole, let the bees carry the treatment in, then plug it and paint the wood. Virginia Cooperative Extension's advice, when control is needed, is to spray an aerosol insecticide into the entrance hole and plug the opening with wood putty.^[1] The details below are what make that work: timing, using very little product, waiting before you plug, and finishing the wood so the next bee moves on.

Make sure it is a carpenter bee

Carpenter bees are large bees, about an inch long, often mistaken for bumble bees.^[1][2] The quick tell is the back half: a carpenter bee's abdomen is shiny and black, while a bumble bee's is covered in hair.^[1][2] The other giveaway is the wood itself.

• The hole. The female chews a round hole about half an inch across, goes in an inch or two, then turns and tunnels along the grain.^[2] It looks drilled.
• Sawdust and stains. Coarse, pale sawdust piles up under the hole, and yellow waste can streak the board below it.
• Where. Bare, weathered or stained wood: fascia, soffits, eaves, siding, deck rails, porch ceilings, fence posts and sheds.

If you are not sure what you are looking at, see how to tell bees from wasps.

Do you need to do anything?

Carpenter bees are native pollinators and are mostly a nuisance. Males hover and dart at people near the nest but have no sting,^[2][3] and females can sting but rarely do unless they are handled.^[2][3]

The case for acting is the wood. A single nest will not cause structural damage, but tunnels that are reused and lengthened over several years, and many bees working the same boards, can weaken wood.^[2] The holes also let moisture in, which speeds up rot,^[2][3] and woodpeckers will peck out the young bees and do more damage.^[1] A hole or two in a fence post can be left. New holes in trim or siding every spring are worth dealing with.

Timing

The best times to treat are late summer, after the new adults emerge and before they hibernate, or early spring before nest building begins.^[2] In practice that means a look in spring as the bees start flying, and another toward the end of summer.

Adult bees overwinter together in existing tunnels,^[2][3] so an old hole may not be empty even in the middle of winter. Treat it before you plug it, whatever the season.

Treating the holes

Use a product whose label names carpenter bees, and follow the label on amount and protective gear. Wasp, hornet and bee aerosols sprayed into the holes are effective, and insecticide dusts labeled for carpenter bee control work when small amounts are puffed into the tunnel.^[2]

The common mistake is using too much. Chemicals are repellent in large amounts, so the goal is to lightly treat the inside of the entrance.^[2] If you overdo it, the bee avoids the tunnel and starts a new one nearby.^[2] A short puff is enough. Treating at dusk, or once you have seen the female leave, means fewer bees tumbling out at you.^[2][3]

Then wait. Leave the hole open for a few days so the bees contact the insecticide and carry it through the tunnel.^[3] The tunnel must be treated before it is plugged, or the bees will chew through the plug.^[2]

Plugging and finishing

Once the hole has been quiet for about a week, plug the hole with a piece of wooden dowel coated with carpenter's glue, putty or another sealant.^[3] A dowel slightly larger than the hole, tapped in and trimmed flush, gives a neat repair that takes paint.

Finishing the wood is what keeps the problem from returning. Carpenter bees usually will not tunnel into painted wood, and stains and preservatives are less reliable than paint.^[3] Fill nail holes and cracks before painting, since those give a bee a head start. For more on prevention, see how to keep carpenter bees from coming back.

Traps

Traps catch searching females but do not clear out bees already in the wood. Most traps are a small wooden box with half-inch holes drilled in the sides and a plastic bottle hung below.^[3] Kentucky's entomologists suggest you hang them in early spring from eaves and overhangs at the corners of the house, porch, deck or shed.^[3] Stick to the overhangs you can reach standing on the ground, such as a low porch or shed roof edge; a trap that would need a ladder is not worth the climb. Use traps alongside treating and painting rather than instead of them.

Stop and call a pro if

• The holes are overhead, high on the house, or under a roof edge. Maryland Extension's advice is to hire a pest control company when the nests are overhead, awkward to reach, or need a ladder or step stool.^[2]
• There are many holes in the same boards, or the wood is soft, split or rotting. That is a carpentry repair as much as a pest job.
• Woodpeckers have torn open long stretches of trim or siding.
• Anyone in the house is allergic to stings.
• The insects are going into a gap in siding or a wall rather than a drilled hole. That is more likely yellowjackets or honey bees, which need a different approach.

Some extension services go further. Penn State Extension's guidance on carpenter bees is blunt: "Chemical pesticide applications should always be performed by an expert."^[4] If you would rather not handle insecticide at all, that is a sound reason to hire the job out. If you hire it out in Virginia, check the license: no one in Virginia may apply a pesticide commercially without a pesticide business license and a certified commercial applicator on staff.^[5]

Getting help on Loclis

You can browse pest control businesses, see bee and wasp removal, look up pest control around Blacksburg, or read the other pest control answers. If the bees have left trim or siding that needs replacing, describe the repair on Loclis and local businesses can quote.