Caulk the holes. I've found that if you paint your wood white, it deters carpenter bees. It also helps deter wasps from building nests. I assume it has something to do with reflecting light, but could also have something to do with the fact that you don't have bare wood for them to be attracted to.

Could be a combination with both, but I've battled these guys over the years in different places and have always found painting the wood the brightest white seemed to really make a difference.

I have several friends who have called in exterminators and all said that there is nothing they can do. I have them both by the cabin and in the tree house. At one time someone suggested putting steel wool into their holes, but that did not last. If you find something that really works, please let us all know!! On the roof overhang by the dining area we have had to nail extra wood to the structure.

Sheila

You can try wood sealer (like for a deck) or shellac to seal the surface. This can prevent them from tuneup not in the first place. They will re-use old tunnels so you'll need to fill those with putty or something. Greetings from Tom Valente!

Everybody --- Thanks so much for sharing what has and hasn't worked for you in the past!

Tom --- So cool to see you over here! Given your background with entomology, it sounds like we should definitely give your advice a try first.