Carpenter Bees

Carpenter bees are large, solitary bees that drill perfectly round half-inch holes into wood to raise their young. Do carpenter bees sting? Males can't, and females very rarely do unless handled, so the real issue is the slow damage to decks, eaves and fascia, not the bee itself.

What carpenter bees look like

The species most US homeowners meet is the eastern carpenter bee (Xylocopa virginica), found from the Atlantic coast to Texas and the Great Plains. The West has several related species, including the valley carpenter bee in California, whose females are solid black and males golden-tan.

• Size: 3/4 to 1 inch, heavy and round-bodied, about as big as a large bumble bee.
• Thorax: fuzzy, yellow in the eastern species, with a bare black spot in the middle.
• Abdomen: shiny, black, nearly hairless. This is the single best identification feature.
• Face: males have a pale yellow-white patch on the face; females a black face.
• Wings: smoky, sometimes with a bluish or purple sheen.

In the South people call them "wood bees". Small, metallic "blue bees" or black bees that nest in pithy stems are usually small carpenter bees (Ceratina), which are harmless and never damage buildings.

Carpenter bees vs bumble bees

If a bee is going in and out of a round hole in your deck rail, it is a carpenter bee. If dozens fly in and out of a hole in the ground or a gap in siding, it is probably bumble bees or yellow jackets.

What carpenter bees do: nests and life cycle

Adults overwinter in old tunnels. In April and May (earlier in the Deep South) they emerge, and you see males hovering at eye level around eaves and decks, guarding the spots where females nest. That is the "aggressive" bee everyone notices.

A female chews a round entrance hole about 1/2 inch across, goes in roughly an inch, then turns 90 degrees and tunnels along the grain. She works about an inch every six days, and you hear the chewing if you stand close. Coarse, pale sawdust collects below the hole.

Inside, she stocks a row of cells, each with a ball of pollen and nectar ("bee bread") and one egg, sealed off with chewed wood. A fresh tunnel is typically 6 to 10 inches long, according to UC IPM, but reused galleries can be extended year after year to as much as 10 feet. Egg to adult takes about three months, there is one generation a year, and new adults emerge in August. They feed on flowers, return to the tunnels to overwinter, and the cycle starts again. One adult lives about a year.

What do carpenter bees eat? Nectar and pollen only. They do not digest wood, unlike termites. They are useful pollinators of blueberries, passionflower, tomatoes and many native plants, although they also "rob" nectar from deep flowers by slitting the base.

Carpenter bees damage: how bad is it?

One season's tunnel is mostly cosmetic. The problems build over years:

• Females prefer to reuse and extend old tunnels, and new females drill next to them. After several seasons a board can carry galleries several feet long and become weak.
• Woodpeckers hammer at the wood to reach the larvae, leaving ragged holes that are far worse than the bees' own.
• Yellow-brown streaks of droppings stain siding below the holes.
• Open holes let water into the wood, which leads to rot.

Favorite targets: unpainted or weathered softwood such as pine, cedar, cypress, redwood and Douglas-fir; fascia boards, eaves, deck railings, pergolas, fence rails, porch ceilings, wooden lawn furniture and log homes. Painted and pressure-treated wood is attacked far less, though not never.

Carpenter bee holes vs other damage: carpenter ant galleries have no neat round entrance and the ants push out fine frass with insect parts (see carpenter ants); powderpost beetle holes are pinhead-size; woodpecker holes are ragged.

Are carpenter bees dangerous?

Not really. Do carpenter bees bite? They have jaws for chewing wood but do not bite people. Females can sting if grabbed or stepped on barefoot, and the sting is about like a bee sting from other species, but carpenter bees do not defend their nests in groups. Kids who catch males for fun are in no danger, since males lack a stinger.

The real risk is to property, and only if you ignore holes for several years.

What to do about carpenter bees

The full step-by-step plan is in how to get rid of carpenter bees. In short:

1. Paint exposed wood. Clemson HGIC rates oil-based paint or polyurethane as the best deterrent and says stains give little protection. Vinyl siding isn't attacked. Even so, paint discourages rather than blocks: bees still drill painted boards when a lot of bare wood or old holes are nearby. Where you can, use hardwood, or cap exposed timber ends with metal flashing or screen (UC IPM).
2. Treat holes at the right time. UC IPM recommends treating in early spring before nesting starts, or in fall when adults are back in the tunnels to overwinter, and doing it at night when the bees are inside. Once a female has sealed her brood cells with wood pulp, the dust can't reach them. Puff a dust labeled for carpenter bees into the hole with a bulb duster. Labeled actives include deltamethrin, cyfluthrin, pyrethrins with silica, and disodium octaborate (borate). Wait a day or two, then plug. Don't breathe the dust, and follow the label.
3. Plug holes properly. A glued dowel, steel wool topped with caulk, or wood putty, then paint. Females prefer to reuse old tunnels, so an open empty hole is an invitation for next spring. An untreated plugged hole may just be chewed back open.
4. Traps. Wooden carpenter bee traps with a jar underneath catch some bees, especially males, and help as a supplement, not a fix.
5. Hard to reach eaves or a log home with dozens of holes: a pest control company typically charges roughly $150–$400 per visit (approximate, varies by region and access).

Avoid spraying blooming plants nearby and protect other bees: treat only the holes.

How dangerous are these products

Carpenter bee dusts go into a half-inch hole, so the amount used is small and pets rarely contact it once the hole is plugged. The risks are breathing dust from a ladder over your head, residue sprinkled on the deck below, and, above all, other bees: pyrethroids are extremely toxic to honey bees and bumble bees as well.

Comparison table

Pyrethroid dustsActive ingredient: deltamethrin, cyfluthrin

CatsCaution

keep away while dusting; sweep up spills below the hole

DogsCaution

same

Kids, pregnancy, allergiesCaution

keep kids away while dusting; adults wear a mask and goggles

Fish, birds, rodents, reptilesDanger

extremely toxic to fish; don't dust over a pond

BeesDanger

extremely toxic; treat only the holes, never flowers

Pyrethrins + silica dustActive ingredient: pyrethrins, amorphous silica

CatsCaution

keep away while dusting

DogsCaution

Kids, pregnancy, allergiesCaution

dust irritates lungs; asthma: don't apply yourself

Fish, birds, rodents, reptilesDanger

toxic to fish

BeesDanger

kills bees on contact

Borate dustActive ingredient: disodium octaborate

CatsCaution

keep away; borates are toxic if swallowed in quantity

DogsCaution

Kids, pregnancy, allergiesKeep out

reproductive toxin: pregnant women shouldn't apply it

Fish, birds, rodents, reptilesCaution

BeesKeep out

toxic to bees that contact it

Aerosol foams/sprays into holesActive ingredient: usually pyrethroids, check the label

CatsKeep out

keep off the deck until dry

DogsCaution

Kids, pregnancy, allergiesKeep out

keep away until dry

Fish, birds, rodents, reptilesDanger

toxic to fish

BeesDanger

Wooden trapsActive ingredient: none

CatsSafe

DogsSafe

Kids, pregnancy, allergiesSafe

Fish, birds, rodents, reptilesSafe

BeesCaution

catch some non-target bees

Pyrethroid dusts (deltamethrin, cyfluthrin)

For people and dogs, used by the label, they're a moderate risk; cats are more sensitive, so keep them off the treated rail or deck and wipe up any dust that falls. Symptoms of overexposure in pets: drooling, pawing at the mouth, tremors, wobbliness. Dusting from a ladder means dust falling toward your face: wear goggles and an N95, work at night with the wind at your back. Don't dust or spray anywhere near flowering plants, hummingbird feeders or water features.

Borate dust

Low toxicity per dose, but a toddler or dog eating spilled powder can get vomiting and diarrhea. Boric acid and other borates are reproductive toxins, so pregnant women should leave the job to someone else.

If something goes wrong

• Dust on skin. Wash with soap and water; pyrethroid tingling fades in hours.
• In the eyes (common when dusting overhead). Rinse with running water for 15 minutes; see a doctor if burning continues.
• Swallowed. Don't induce vomiting; call Poison Control at 1-800-222-1222 with the label.
• A pet licked dust and is drooling or trembling. Call your vet or ASPCA Animal Poison Control at (888) 426-4435. More: pet-safe pest control.

What people who dealt with it say

We read through homeowner threads on r/HomeImprovement, r/homeowners and r/pestcontrol. The same patterns come up again and again:

• "Harmless pollinators" vs "they ate my fascia." Both camps are right. A few holes in a swing-set beam or deck rail are cosmetic. Commenters with a beam in that state are usually told a 4x6 is fine unless it looks like Swiss cheese. Owners who ignored them for years report replacing whole fascia runs or porch roof framing. One reported about $5,000 for new fascia, and log-home owners describe hollowed logs.
• Spray-and-plug alone often fails. A common story: someone sprays a foam or aerosol into the holes, kills the current bees, and new bees move into the same holes a few weeks later. People who puffed a deltamethrin dust in with a duster and then plugged the holes report the problem ending within a couple of weeks.
• Paint helps but isn't a force field. Several people saw bees bore into freshly painted, even pressure-treated, fascia. Bare wood and existing holes nearby keep the area attractive.
• Traps are the favorite add-on. Wooden traps with a jar underneath (bought or homemade from a block with angled holes) get steady praise as a way to thin the numbers, especially when hung right next to the damaged wood. Nobody credits them with ending a big infestation alone.
• "Bee houses" to lure them away: mixed to negative results. Many store-bought bee houses are actually built for mason and leafcutter bees, not carpenter bees.
• Hanging a paper bag stuffed with plastic bags as a fake wasp nest is widely repeated, and a few people swear by it, but there's no research behind it. Treat it as harmless folk advice.
• Badminton or tennis rackets are the most popular way to deal with the males that hover around the deck. Since males can't sting, that's safe, but it doesn't touch the females doing the drilling.

When to call a pro

• Many holes on high eaves or second-story fascia that you cannot reach safely from a ladder.
• Structural members (beams, posts, deck joists) are tunneled.
• Log homes and large cedar-sided homes with recurring problems.
• Woodpeckers are already tearing up the siding.

For other bees around the house, see our guide to bees.