This shows a lot of black stuff on some of the branches of my cherry tree and the leaves are beginning to curl. Has anyone any idea what it may be and what I need to do about it.
Regards.
(http://www.allotments4all.co.uk/smf/gallery/13821-130614165133.jpeg)
I've done a lot of looking around and I'm pretty sure it's blackfly.
I noticed some iffy looking leaves on my cherry tree this morning. I haven't had a proper look yet but I'm fairly sure I'll find aphids in the curled leaves. I can't quite make out from your picture if yours are blackfly, but I think it likely if you have lots of little black flies about the same size as greenfly. I try and knock them off with a jet/spray of water from the hosepipe (but not in full sun) not always easy if the leaves are badly curled.
Yes it's hard to tell from the photo but it sounds like blackfly - or aphids and then sooty mold colonising the sugary mess the aphids leave.
I've got terrible cherry trees this year - aphids, cherries rotting before they can ripen (no idea what that is), snails living in there too! I haven't had time to do anything about it.
Squirting or wiping aphids off is fiddly, and it's hard to do and hard not to damage leaves. But I don't know of anything else you can do. Even if you buy a chemical pesticide, you'd have trouble getting into the under side of curled leaves anyway.
I don't know how professional growers do it, I've found cherries a real pain!
I remember similar leaf distortion on a cherry we had outside the back door when I was a kid. It was always smothered in blackfly.