Cherry Tree bug

Hi, I live in NYC and I have a cherry tree about 8 feet tall, the new leaves at the end of the branches are infested with a black bug. See atached picture. It curls up the leaves. I noticed it last fall, but now they are back. Does anybody know of a non-toxic way I can get rid of them?
Thanks

 

They might be black aphids, use soapy water, the soap coats there bodies and they sufficate.

 

Thank you. I will give it a try.