Carpenter Bees

Are these bumble bees that are chewing holes in my wood? Each year, we get calls asking this question. In fact, they are carpenter bees, which closely resemble bumble bees, that are chewing holes in the wood. They bore perfect round holes, often leaving piles of sawdust below. They will also hover in the air and sometimes buzz around your head.

Carpenter bees are large, 12.5 to 25 mm long with the abdomen black and shiny instead of covered with yellow hairs like bumble bees. Males have yellow faces while females are black. Males will sometimes fly aggressively and hover around intruders in their territory but it is all show as they do not possess stingers. Females have stingers but are docile and rarely sting.

These bees become a nuisance when they start boring holes in wood such as around the trim near eaves, facia boards, soffits, porch ceilings, outdoor wooden furniture, decks, railings, wood siding etc. They prefer untreated wood but will chew through wood that has been stained or only lightly painted. Most types of wood can be attacked but softwoods are preferred.

Carpenter bees over winter as adults within their old nest tunnels. In the spring, females will either start new tunnels or reuse old ones. The female, who will chew a hole about the diameter of her body using her mandibles, forms the tunnels. Tunnels go in for a short distance and then turn at a right angle and follow along the grain of the wood. New tunnels will be 10-15 cm, but older galleries can be extended up to 3 m. Piles of sawdust often accumulate under the holes. The female will provision cells, starting at the back of the gallery with a mixture of pollen and regurgitated nectar. She lays an egg on top of the mass then seals the cell with chewed wood and repeats the process working back out to the entrance. The interesting part is that the last cell formed is the first to hatch so that the bees will emerge in reverse order starting at the entrance. Development time is 30 40 days and there is one generation per year. These bees will infest the same areas year after year which results in numerous holes which can deface wood or log siding or gable areas.

Another problem associated with carpenter bee holes is wood pecker damage. Woodpeckers will open up the holes to get the larvae inside the tunnels and can do extensive damage over time. Hairy woodpeckers will go through one inch pine boards trying to reach the larvae.

Control of Carpenter Bees

Control involves treating directly into each hole as well as treating the soffit areas or other areas that the bees are infesting.