Despite their name, carpenter bees are not handy with a hammer. They can be a destructive force to your home and its wood structures.
Carpenter bees get their name because they excavate galleries in wood to create their nests. They don't eat wood - they're much like other bees in that they consume pollen and nectar. In fact, carpenter bees are important pollinators of flowers and trees, so in that regard they are beneficial.
It's only when they decide to build nests in your fence, deck or the siding of your house that they make a nuisance of themselves. They can cause considerable wood damage if several generations begin making themselves at home.
Big and slow
Carpenter bees are usually large and slow-flying. The most common type is about three-fourths to one-inch long, black, with a shiny surface. The underside is covered with splashes of bright yellow, orange, or white, and the upper side of the abdomen is black, glossy, and bare. Carpenter bees have a dense brush of hairs on the hind legs.
They are often mistaken for bumble bees, except bumble bees have a yellow abdomen and large pollen baskets on the hind legs. Various species of bumble bees and carpenter bees are similar in size. Bumble bees are very unlikely to nest in wood.
Carpenter bees cause mostly cosmetic damage, by drilling round holes into the wood. Over time extended infestation can cause structural damage, but it is fairly rare. However, tunnels in the wood can be several feet in length.
Prevention
The best way to keep carpenter bees away is to paint wood surfaces with a polyurethane or oil-base paint. Every once in a while inspect painted surfaces to make sure the coating is intact. It's exposed wood that the carpenter bee targets.
In addition to exposed wood, carpenter bees prefer soft woods, like pine. That means an untreated, or weathered deck can be a prime target. Unfortunately, wood stains will not deter carpenter bees. They'll simply drill right through it.
When you find holes in your wood surfaces, fill them with caulk. If the bees are inside, they won't try to drill their way out.