How much of a tree is it OK to prune out in one shot?

I have this Japanese maple that has a main trunk that hasn’t leafed out, which I think might have verticillium wilt or phytophthora (thanks, Dax).

The piece in question comprises 1/3 - 1/2 of the tree, and I’m not sure if it’s a good idea to prune it all out at once - I thought it could potentially alter the tree’s balance too much and stress the roots?

Anyway here is a picture where you can see the relative size of the affected part. Any advice as to the best way to proceed will be much appreciated!


If a branch is dead, you can’t hurt the tree any more if you take the branch out, no matter how big it is.


Cut about 50% of mine a year ago and it is going wild with new growth this year. And that wood was alive. If it’s dead cutting it out will actually help it. The missing spot will fill back in.

Thank you both. It’s not dead: in fact some of it began to leaf out a few weeks ago, but then all the leaves wilted and died. The wood is still green and flexible. But I’m thinking it will die so I guess I should just prune it out now. I take it there’s no chance of it reviving, and no reason to wait?