How To Treat Carpenter Bees

If you own a wooden structure with exposed wood siding, logs or a wooden deck, chances are high you have encountered Carpenter Bees. These rather large insects are found in abundance on every continent minus Antarctica. They are close in appearance and size to a Bumblebee with the exception that they do not have hair on their abdomen, and only the female Carpenter Bee stings when provoked.

How Carpenter Bees Breed

They are solitary insects and do not live in colonies like traditional honeybees. Instead, the female carpenter bee will drill a hole in dead wood that is approximately one-half inch wide at a rate of one inch every five to six days. She will use her large mandibles in combination with vibrating her body to create a drilling like action.

In this process they do not consume the wood, they are simply excavating the wood to create a home for their future brood. The male Carpenter Bees will hover near the vicinity of the nest to help keep guard.

Carpenter Bees emerge from their holes in the springtime around April or May. They are highly active during this period in which they enlarge existing tunnels or excavate new ones and gather food. They mate with one another, and the females lay their eggs in a series of sealed off chambers. Each chamber contains food called “bee bread”. This is a mixture of pollen and regurgitated nectar. When the eggs hatch into larvae, they will have food within their chamber to sustain themselves until late summer when they emerge as young adult Carpenter Bees. These young adult male and female bees will hibernate in the tunnels during the winter.

carpenter bee

Effect of Burrowing on Wood

If left untreated, Carpenter Bees can do damage to your structure over time. We have had our own experience with Carpenter Bees attacking our home. Several years ago, we noticed they were drilling a series of holes into the underside of the outside fascia boards of our deck. At the time I sought advice from one my coworkers on the best ways to handle the Carpenter Bees. I was advised to treat each hole individually. 

Treating The Holes

Carpenter Bees usually drill up a short distance and then make a ninety degree turn and continue excavating. Using a straightened-out metal coat hanger with a slight bend on the end, I inserted the slightly bent end of the hanger into the entrance hole and was able to get the hanger to go around the sharp bend. I continued to push the hanger deeper into the hole, going through each sealed off chamber, until it would no longer go any further. I then removed the hanger and sprayed liberal amounts of WD-40 into the hole using the special red tip extension tube. Using the extension tube, I allowed for the spray to reach around the ninety degree turn inside the nest. Next, the entrance hole was closed off with sealant. This was repeated for each entrance hole that I could find.

Repairing the Holes

Finally, after this was complete a coating of paint was applied to the underside of the fascia board where most all of the holes were found. This rather smooth surface acts as somewhat of a deterrent to the pests. This process worked well in our case and greatly reduced the infestation.

For log and timber homes, once the holes are treated and dry, they can be sealed with Energy Seal in a color that is close to the log color, and stained over. 


Unfortunately, a treated wood pesticide wouldn't work in preventing Carpenter Bees, as they do not injest the wood. The best prevention we've found is having a wood surface that is smooth and clean. We've asked many homeowners and have found that homes finished with Advance Gloss topcoat deter the bees. They are mostly attracted to rough and decaying wood. 

Parting Thoughts

The technique used to treat the holes in the example above works well if done in the summertime when the larvae are present. However, in the fall, winter or early spring perhaps the coat hanger would not be necessary since the chambers would be empty of Larvae. Furthermore, each hole would still need to be treated with insecticide or spray such as WD-40 and sealed off. If Carpenter Bees are not dealt with, you could potentially have additional problems such as Woodpeckers seeking the larvae for food.

For more tips and advice for dealing with Carpenter Bees please visit our website at and click on the link for the DYI section at the bottom. Click on Pests and then select the technical tip for Carpenter Bees.

Last modified on Friday, 01 October 2021 22:05

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