Carpenter Bee Control: Stop the Tunnels in Fascia, Decks and Trim

The carpenter bee in Pennsylvania

If a big bee is hovering under your eaves or at the end of a deck rail in spring, it is almost certainly a carpenter bee. Penn State Extension says there is only one species of large carpenter bee in Pennsylvania, Xylocopa virginica. It looks like a bumble bee, but the top of the abdomen is mostly bare and shiny black, while a bumble bee's abdomen is covered in hair, much of it yellow.

Carpenter bees are not social. Each female builds her own nest by tunneling into wood, though several may nest in the same board. They do not eat wood. The tunnels are shelter and nursery space, and the bees feed on nectar and pollen. University of Maryland Extension points out that they are native pollinators and that control is only needed when they are damaging wooden structures. So our work is treating galleries in your house, deck or outbuildings, not bees on the flower beds.

What they do through the year

The yearly cycle explains why timing matters so much for treatment and repair.

Gallery damage to fascia, decks and siding

A female starts with a nearly perfect round hole about half an inch across, usually bored against the grain. About an inch in, she turns at a right angle and tunnels along the grain. University of Maryland Extension puts a typical gallery at 6 to 12 inches, and because tunnels are cleaned out and lengthened by bee after bee each year, old nests can run much longer.

One bee's hole does little harm. The damage comes from years of reuse and many bees working the same boards. Penn State notes bees prefer wood more than two inches thick, and a University of Kentucky entomology fact sheet lists softer woods such as cedar, cypress, redwood and pine as favorites. On houses around here that points to:

• Fascia boards, rafter tails and the underside of eaves and soffits.
• Deck joist ends, rim boards, railings and stair stringers.
• Wood siding, cedar shakes and exterior trim.
• Porch ceilings, doors, windowsills and pergolas.
• Barns, sheds, fence posts and wooden outdoor furniture.

Stains, sawdust and woodpeckers

Look below the holes. As she digs, the female pushes coarse, sawdust-like material out of the tunnel, and she leaves sticky yellow waste that spreads in a fan shape on the siding or trim. University of Maryland Extension notes those stains turn black with mold as they age, which is often what homeowners notice first.

The holes also let water into the wood, and that speeds up rot in fascia and deck framing. Woodpeckers add to the damage when they tear into tunneled boards to feed on the developing bees, turning a neat half-inch hole into a ragged gouge along the gallery. If woodpeckers are hammering at your fascia in summer, check for carpenter bee holes nearby.

Stinging: males cannot, females rarely do

The bee most people notice is the male, and male carpenter bees cannot sting. Penn State describes males hovering near the nest, darting at other insects, and flying up to people who move quickly or wave a hand. It looks aggressive but it is territorial display.

Females can sting but seldom do. Penn State says a female has to be seriously provoked, such as being handled, before she will. For most families the real issues are the noise, the stained trim and the wood damage, not stings. Wasps and yellow jackets do sting, and they are covered on our page for wasp and hornet nest removal.

What treatment looks like

We follow The Davis Inspection Standard, explained on our four-step process page. First we confirm they are carpenter bees and not another bee or wasp. Then we map the active holes and name the conditions: bare wood, old stain that has worn off, nail holes and cracks that give a bee a head start.

Treatment goes directly into the active gallery openings with a product labeled for carpenter bees, applied per the label. The holes are then left open for a few days, because Penn State and the University of Kentucky both explain that bees need to pass through the entrance to contact the material and carry it through the tunnel. Plug a hole too early and the bees chew a new exit or start again next to it.

Once the gallery is inactive, holes get plugged with a wooden dowel, wood putty or a suitable sealant, and the wood is painted or finished. Spring, when bees are first drilling, and late summer are the usual treatment windows. Many galleries are overhead on fascia and eaves, which is why Penn State notes many homeowners hire a licensed company for this work. We tell you before we start how long to keep people and pets away from treated areas, per the label.

Prevention: paint, seal and replace

Carpenter bees go after raw, unfinished or weathered wood. Well-maintained painted wood is rarely attacked, according to University of Maryland Extension, and Penn State notes that stained wood is not usually protected. The University of Kentucky fact sheet calls paint the more lasting solution, with stains and preservatives less reliable.

• Fill nail holes, splits and cracks with caulk or putty, then paint bare wood, especially boards with a history of holes.
• Keep up with repainting fascia, trim and deck rails as the finish wears.
• Consider vinyl, aluminum or other non-wood coverings for fascia and soffits that get hit every year. They exclude carpenter bees.
• Replace boards that are heavily tunneled or rotted rather than patching them.
• Keep garage and shed doors closed in April and May while females are searching for nest sites.

Carpenter bees, carpenter ants and home sales

Carpenter bees are one of the wood-destroying insects recorded on the NPMA-33 form used in real estate sales, so old holes and stains can show up on a WDI report for a home sale. If you are finding coarse shavings and large black ants instead of round holes, read about carpenter ants in damp wood.

C.R. Davis III & Sons is family owned, a Pennsylvania family corporation since 2003, licensed with the Pennsylvania Department of Agriculture and insured. Call (610) 935-9130 or reach us online to have the holes looked at before the next generation moves in.