Wooly aphid on crabapple tree
 

As the subject says, I have an infestation of wooly aphid on a crabapple
tree. It seems to be confined to this tree only although there are half a
dozen other fruit tree. The tree is pretty old, gnarled and arthritic
looking all in all.

How do I get rid of it ? What can I spray it with that works - I'd imagine
the white wax is effective against most sprays.

Or is it probably better just to bite the bullet and replace it with another
new fruit tree ?