BTW, this stuff seems to have worked well. I painted untreated lumber with a final coat of this on the underside and sides of a porch railing and the carpenter bees left it alone.
Also ... have been experimenting with Permethrin 10% -- seems to work well.
1. applying diluted with water with a pump sprayer to underside / sides of wood structures
2. making a vaseline + permethrin gel to inject into existing holes and kill emerging larvae