Apple On Edge

I acquired a rather nice Nagasaki crab at the end of last season about 10" tall that is showing signs of distress now. It budded out ok, if a bit more weakly than my other apples, but now some of the newly sprouted leaves are shrivelling and drying. It may be as many as 30% of the shoots that are affected so far and they tend to be toward the top of the tree. The other shoots are not showing much sign of extension.

I pulled the tree out of the pot to check the roots and found some white fuzz on some of them. I had issues with wooly aphids last year so I cut out the roots I could see that were affected and put it into a slightly larger pot with fresh turface as potting medium. I watered it in well and sprayed with a systemic insecticide I know has worked against the wooly aphids before. I gave the soil surface a few sprays as well.

That was a couple of days ago and have seen no change for better or worse so far. None of my other apples seem to have the issue. Any ideas on what it could be and have I done the right thing if its wooly aphids?