A chainsaw, applied at the base of the tree.

OK, not quite that drastic, but pretty close; I started following dead wood a year ago last fall and followed tunnels down every limb to the trunk, which was riddled with tunnels. I kept cutting back to sound wood and ended up with what looked like a baseball bat sticking out of the ground.

The next spring it sprouted a glorious canopy so well-shaped I wished I had done this years sooner; I painted the trunk with the white paint-drywall mud blend and so far so good.

Applenut

That is an interesting combination. It sure would not hurt to try.