Help with crown and trunk rot on Apple

So if there is no green ( alive) cambium under that whole discolored area . No mater what you treat it with it will not heal.
Looks like , from the burr knots , that is root stock ,up to the first branch, and likley has fire blight ( or other) moving up.
And ( likely moving down too )
If there is no green tissue in that area , carbohydrates from top can not feed root and it will die.
If so ?..
The only hope I can see is …
Take a propane torch to the upper end of said blight , until it boils.! ( killing the blight)
Then graft 3 or so tall root stocks into it ,above canker into healthy wood . ( needing done soon ) if you can get rootstock?
This is a long shot , and a project.
. But if successful ?
How cool,… multiple roots / multiple variety
Best of luck ,… Whatever you do!

Oh man😭. Either way it sounds like my tree is determined to die. I will look into this option as well. Thank you for the input.

By the way this isn’t the same person that has the hort tube channel on YouTube is it?

No channel

I’d still try it. The leaves still seem to be hanging in there. I would expect the leaf tips to go black by this time if there was no working cambium left.

:+1:
So regarding drench. Should I apply the same mixture as a bark spray? Also can I drench with the Pentra bark or should I mix up two different mixes

I diluted the bark spray down (along with pentra-bark) and used it as the drench.

Ok cool! Thank you