It's a tricky deal working with fruit trees.
I am certainly not an expert but I have learned a few tricks along the way.
Main thing I learned.. It's a balance game.
There are a few chemical treatments out there, I am not to sure if I trust many of them on trees producing something I would want to eat.
I have used a copper suspension on chokecherry, apple, plum etc.. Timing and concentration build up have to be considered even with that.
Many chemical treatments that are known to really work well to regain control of infections are rather scary to me how toxic they seem.
The copper suspension works ok, but really is only best if used with mechanical means of removing infections, and keeping the possibilities of infections low. A healthy tree helps a LOT to keep the infections at bay, but many things that keep trees healthy normally can cause fungi.
Keeping them watered to help weather a hot/dry spell can lead to root rot, or infection.
So you can probably see where I am going with this.
I am guessing birds have a good deal to do with spreading black knot, so I have a few things in place to lure them away, and deter them from the fruit trees close to the house.
Like I said its a balance game, you just have to keep an eye on the plants and trees and see what works, immediate danger from the heat might be the best thing to worry about. but if it were me I would move the leaves back and let dry every so often and inspect the trunk.
