copper green in live trees
A while back I had a leak in my roof that caused some dryrot in a crawl space. After the leak was fixed they sprayed "copper green" on the affected wood to kill the fungus. (Note that this was not a preventative measure but a fungicide used to kill an established fungal colony.) Apparently copper green is a copper napthalate complex in an organic solvent that penetrates deep into the wood and is super deadly to fungus.
Meanwhile, I have several huge and beautiful valley oaks on my property. Probably 10 or 15 years ago someone trimmed some huge (2' diameter) branches and now many of those have big rotten holes in the middle. My understanding is that the wood on the interior of the tree is essential "dead." So why not spray it with a can of copper green? If it's already non living wood spraying it shouldn't affect the living part of the tree and maybe I can stop or slow the rot.