I can't remember the name of the borer that loves maples but, I had this problem for a while. I've read that this occurs when a branch is to exposed to the sun and it attracts them to lay their eggs on the warm branch. I noticed this as an issues with me when pruning in early summer exposing branches that would normally be under shade.
I think I may need to try and transplant one of my trees after seeing your success. I would not of thought it possible.
I think I may need to try and transplant one of my trees after seeing your success. I would not of thought it possible.
