The large black bees drilling into your deck, fascia, or fence posts are almost certainly carpenter bees. They’re solitary insects that bore perfectly round, half-inch holes into wood to lay their eggs, and left unchecked, they’ll return to the same spots year after year, extending tunnels that can reach 6 to 12 inches deep. Getting rid of them involves a combination of treating active nests, trapping foraging bees, sealing old holes correctly, and making your wood less inviting in the first place.
Confirming You Have Carpenter Bees
Carpenter bees are often mistaken for bumblebees, but they’re easy to tell apart. Carpenter bees have a shiny, mostly hairless black abdomen, while bumblebees are fuzzy all over. The males are the ones that hover aggressively near your face. They can’t sting. Females can sting but rarely do unless handled directly.
The clearest sign of an infestation isn’t the bees themselves but the evidence they leave behind. Look for small piles of sawdust on the ground below wood surfaces, perfectly circular holes about half an inch wide, and fan-shaped yellow or brownish stains running down the side of the structure below the holes. Those stains are a mix of pollen and bee waste. Favorite nesting spots include deck rails, porch ceilings, fascia boards, fence posts, soffits, siding, and even picnic tables, especially when the wood is near gardens or flower beds where the bees feed.
Treating Active Nests
How you treat a nest depends on whether a bee is actively inside. If you can see fresh sawdust falling from a hole or hear buzzing inside the wood, the female is currently drilling. Spray a contact insecticide (wasp and hornet spray works) directly into the hole. She’ll back out quickly. Once she’s gone, fill the hole immediately with caulk or putty so no other bee claims it.
If the hole looks empty or you’re unsure whether anyone’s home, take a different approach. Insert an insecticidal dust like boric acid into the entrance and leave the hole open for several days. This gives returning bees time to contact the dust and spread it through the tunnel system. Only after that waiting period should you seal the hole.
For holes you discover during summer, larvae may already be developing inside. Run a length of flexible wire into the tunnel to break through the pollen plugs that separate individual egg chambers, then apply dust or aerosol insecticide before sealing. The same approach works for holes found in fall or winter, when adult bees may be hibernating inside the tunnels.
The best time to do this work is early evening or early morning, when bees are least active and most likely to be inside their tunnels.
Sealing Holes the Right Way
This step trips up a lot of people. Your instinct might be to grab silicone caulk or expanding foam and plug every hole, but that’s actually counterproductive if you’ve dusted the tunnels first. Foam and caulk fill the interior space, which means any larvae that hatch inside won’t be able to crawl through the dust treatment. They’ll simply chew a new exit hole and bypass the insecticide entirely.
Instead, seal treated holes with a cork or a short wooden dowel. These plug the entrance tightly while keeping the interior tunnel open, so hatching bees have to move through the dust to try to escape. Once you’re confident no live bees remain (give it a few weeks), you can fill the holes permanently with wood putty, sand them smooth, and paint or stain over them.
Using Traps to Reduce Numbers
Carpenter bee traps are simple wooden boxes with angled entrance holes that mimic natural nesting sites. Bees enter, follow the tunnel downward, and drop into a collection chamber they can’t escape. They work best as a complement to direct nest treatment, not a replacement for it.
Placement matters more than the trap itself. Hang traps near current or previous nesting sites, at the corners and peaks of structures where wood gets warm sun exposure. Carpenter bees prefer warmth, so a trap tucked in deep shade under an eave won’t attract much attention. Secure traps firmly so they don’t sway in the wind, and keep them clearly visible rather than hidden.
Spring is the ideal time to set traps, since that’s when carpenter bee activity peaks and mated females are actively searching for nest sites. Adding a dead carpenter bee to the collection chamber can help, because the pheromones act as a natural lure. Before you hang traps, seal any existing old holes on the structure first. If bees have easy access to a familiar tunnel, they’ll choose it over a trap every time.
Natural Repellents
Several plant-based scents deter carpenter bees from landing on and investigating wood surfaces. Citrus oil, lemongrass, citronella, peppermint, and clove oil are the most commonly used. You can buy premixed sprays containing these oils or make your own by adding 15 to 20 drops of essential oil to a spray bottle of water with a small squirt of dish soap to help it mix.
Spray the solution directly on wood surfaces where you’ve seen bee activity, focusing on existing holes, exposed grain, and sunny-side boards. Reapply every week or two and after rain. These repellents won’t kill bees or drive them out of established tunnels, but they can discourage new drilling on treated surfaces. They work best as a preventive layer after you’ve already dealt with active nests.
Preventing Them From Coming Back
Carpenter bees strongly prefer raw, unfinished, or weathered wood. Well-maintained, painted wood is rarely attacked. That single fact is your most powerful long-term defense.
Paint or apply a polyurethane finish to all exposed wood surfaces, especially fascia, soffits, deck rails, and porch ceilings. Stain alone offers some protection but less than paint, because bees can still detect and access the wood grain underneath. If you’re building or replacing a structure, consider using hardwoods, composite lumber, or vinyl-wrapped trim, none of which attract carpenter bees.
Repair existing damage promptly. Nail holes, splinters, cracks, and old carpenter bee holes all give females a head start into the wood. Fill cracks with wood filler, sand down rough spots, and keep painted surfaces touched up. The goal is to present a smooth, sealed surface with no easy entry points.
Finally, keep in mind that carpenter bees are important pollinators. If their nests are in a spot that doesn’t threaten your home’s structure, like a dead tree at the edge of your yard, consider leaving them alone. The bees causing real concern are the ones tunneling into load-bearing beams, deck supports, or siding, where years of expanding galleries can lead to genuine structural weakening. Focus your efforts there.