Beautiful cherry tree is sick - how to treat?

[Leavestumble]

I have a beautiful cherry tree right outside the window above the kitchen sink. It has struggled with the wet spring, flowering early. Last few weeks it has lost a lot of fullness in the leaf, and black parts developed on the leaf... and now this white fungus! Full horror! Can it be treated? Would be very upset to lose the tree.

Whats on the trunk looks suspiciously like woolly aphid which we get on our apple tree.
blast with a hose with decent pressire or pressure washer or hope some long tail tits come alone. We had a lot more than that which hasnt harmed the tree.
for the black leaves, remove them. Hopefully drier weaher will heplp

If you use a cloth to remove the aphide it goes a dark red iirc

Agree with @Wherearemymarbles - probably woolly aphids & the damaged leaves could be plum aphids which affect all plum families members (cherry, plum, apricot etc). Remove the leaves.
We've had a really weird year with our fruit trees. Every year until this year our cherry (Stella) has been infested by aphids. Late last year I got an apricot & a plum tree. I also read up on aphids & read they don't like garlic/onions, so planted garlic chives around the base of the cherry tree.
Come spring, aphids infested the new plum & apricot (& everything else in the garden practically) BUT absolutely nothing on the cherry? It look magnificent; no curled leaves, no sticky residue etc. Now I'm not sure if it was the garlic chives or if the aphids just went for the new plants instead. Just really odd - but I'm planning on under planting my plum & apricot with garlic chives & wild garlic this year & see what happens next year.