Carpenter Bee Holes
Summary: Carpenter bee holes are often discovered in unpainted, exposed wood on siding, window trim, decks, and outdoor furniture. But, don't look upon these holes as damage. Look on the bright side. You've got perfect holes and you didn't even need a drill.
Carpenter bees don't build hives and they don't make honey. They are solitary insects that burrow into wood to build a gallery where they live and lay eggs. Although carpenter bees don't eat wood or cause the extensive damage to wooden structures that termites do, Carpenter bee holes can become an eyesore. Our instincts tell us that we shouldn't mess with big, black bees, so what should we do?
Wait for nightfall if you are thinking about doing some type of pest control treatment. This is when the bees are not active and will be asleep in their chambers. Directly treat the hole entryway with a dust pesticide specified for use on bees. Pesticides containing cypermethrin, such as Demon WP can be used for the job. Leave the holes open to allow the bees to enter and exit freely. This gets the dust on their bodies. When they clean it off they will be killed by the pesticides in the dust.
As luck would have it, carpenter bees don't sting. At least, they sting very rarely. The males don't even have stingers and the females are too busy laying eggs to bother with attacking something as large as a human being. The females are usually inside the wood, hollowing out the chambers where they will lay their eggs. The female bees burrow about an inch into the wood, then dig sideways, going along the grain of the wood. The galleries can become very long if the bees are allowed to return to the same place year after year and continue to extend the length of the tunnels.
Carpenter bees look a lot like bumble bees. They are fairy large, but the difference is that they don't have the yellow hairs on their abdomen like bumble bees . Also, bumble bees sting and carpenter bees do not. If you see a lot of the bees with black abdomens buzzing around the holes in wood, these are the male bees marking their territory and trying to attract the attention of a female. They are behaving a lot like teenagers at the mall. Remember, the male bees don't have a stinger, but before you start swatting at them, make sure they are carpenter bees and not bumble bees or wasps!
Here's a trick to kill the remaining eggs. After you no longer see adult carpenter bee activity, stuff the holes with a small piece of cotton ball soaked in nail polish remover to help kill the eggs. The bees will push out the cotton if the holes are still actively used, and the cotton will remain in the holes if they are no longer used. Once you have made sure that the holes are no longer active you can fill them up with latex wood putty, or by gluing wooden dowel rods into the holes to plug them up. Sand down the dowel rods and coat them with paint to make them match the rest of the wood.
To prevent carpenter bee holes, you should use pressure treated wood for all outdoor wood on your house. (Note: As of December 31 2003, the preservative chromated cupric arsenate (CCA) was phased out in pressure-treated lumber intended for residential use (decks). To replace CCA, the lumber industry began using amine copper quat (ACQ) and copper azole (CA). Reports are that these materials do not repel carpenter bees as well as the former chemicals.) Play sets or swings should also use pressure treated wood. Manufacturers claim treated wood will protect against carpenter bee attacks. The bees supposedly only attack unpainted wood, so by doing a good paint job on exposed wood you will prevent the bees. Use a good primer, two layers of high quality paint, and a finish. A simple stain will not be enough to prevent the bees. Some paints containing pesticides are available, but I wouldn't recommend them because they wear off fast and don't always work. A pesticide containing paint may claim to last for several years, but only if not exposed to water or sunlight. Of course, any paint used on an outdoor surface inevitably will be exposed to both water and sunlight. Funny how that works. If that doesn't do the trick (Evidently, some bees have not been informed that they are not supposed to bore through painted surfaces.), purchase a liquid pesticide containing cypermethrin and spray the surfaces of the wood under attack. Please read the label carefully and follow the directions. Don't get creative with pesticides!
Woodpeckers love to eat carpenter bees, so if you see any banging their heads against the side of your house, this might be the reason why. The woodpeckers might solve the problem for you, but they will also put even more small holes into the side of your house.
Carpenter bees are a pest control problem you can take care of yourself and the bees will be back year after year if you don't. So, hop to it.