[simonwatson]

Any suggestions for what this might be on a sweet cherry tree? It's affecting most of the growing tips but leaves from last years branches are fine.

[Nobbie]

Looks like aphids to me, I think you can see some on the underside of one of the leaves.

[jaydig]

Mine are the same this year. Uncurl the leaves and you'll find they are full of nasty aphids.