Save your Fences! Spring is here and so are the Carpenter Bees. Van Foster has kindly recommended a solution that he has found to be effective for managing these pests, found at http://www.e-bug.net The kits sold on this website contain a Drione dust to insert into the bee holes to treat the nests and an insecticide for spraying the fence to prevent future holes from being created. Also, corks are included for plugging the old holes.
More information on Carpenter Bees can be found on Wikipedia here.