My 12 year crepe myrtle has something eating the bark, with huge gashes extending up the tree. Seems otherwise healthy. What could it be? It has seemed fine. I just noticed these huge lengthy gashes on several of the big trunk areas. Must have been there for a while. Bark just pulls away and looks like what might have been webs inside. No bugs visible now. Is there a spray for this? Would hate to lose my 12 yr. old tree.