[bluealf]

All the outer extremity leaves have curled and looks like a tiny black bug on the underneaths of the leaves.

What are these ?

There was some on my apple tree also but they have obviously all jumped to the cherry and the apple is sprouting new growth now.

Will a wash of soapy water do some good ?

[SG6]

Black fly, they will infest the ends of all the branches.
You need to get rid of them by whatever means you choose.

[Trillium]

Sounds like you have black cherry aphid. Here's a link for control.

http://jenny.tfrec.wsu.edu/opm/displaySpecies.php?pn=420

[bluealf]

Sounds like you have black cherry aphid. Here's a link for control.

http://jenny.tfrec.wsu.edu/opm/displaySpecies.php?pn=420

Thats the * all right, shame its a bit late to spray after the leaves have curled  but i shall be waiting their return in autumn 

Thanks for that

[Dominic]

This happened to my cherries in the first year but not the second.
Didnt do anything.

[paintedlady]

be aware that ladybird larvae are feeding off these aphids in and around the garden about now in case you were thinking of chemical warfare 

[Jay The Digger]

Had exactly the same problem with my cherry this year.  All leaves at the end of the branches rolled up and was infested with blackfly.  Shortly after the tree was covered in hundreds (not an exaggeration) of ladybird pupae (Harlequin I'm sorry to say)

To make matters worse whilst I was on holiday the birds stripped the tree of every single fruit.  Didnt even manage to find one to taste. 

Am going to buy an old fishing net next year to cover it with.