Here's something your local garden shop can help you get. To treat the carpenter bee holes, use Drione dust and a duster. As the female enters the hole she will drag the dust into the nest and kill all the larvae. Drione lasts for many months and is very safe. After 2 or 3 days plug the holes.
Natural cork does a good job as a hole plugger.
This makes it easy to see new activity and keeps the dust inside to kill the larvae. Before posting a message, please be sure you are in the appropriate category. No advertising is allowed on HGTV's message boards. Do not post messages that blink, scroll, or contain wingbats, colors, or large fonts. Off-topic postings will be deleted at our discretion.