You haven't had an answer yet, and I was thinking maybe you should contact a good nurseryman or local botanical garden. You don't want to lose your tree. I did find the link below, but don't know if this would be it or not.

You could also post on the Trees Forum.

Good luck.

Susan

Here is a link that might be useful: Borer

Your description doesn't ring any bells at all, which makes me wonder if you have a newly introduced pest that the "ag cops" should know about. Each county has an Agricultural Commissioner's office, which is responsible for watching for introduced pest species (they're the ones that set out japanese beetle monitoring traps, etc). You might want to call your local office and report it. Their job also includes helping homeowners with this sort of id and appropriate control measures, in case it turns out to be something common.

Here is a link that might be useful: Ag Commissioners office

Here is a picture of the Sycamore Borer. The UC Davis IPM website says that no treatment for the borer is recommended because the trees are tolerant of infestation (the tree has coexisted with this native pest for a very long time).

Ryan

I have been thinking that maybe what you're seeing is a joint effort .... the flicker/woodpecker makes holes in the trees and the Carpenter Bees move in.