aphids/green fly on a plum tree
 

just noticed this morning that there are a number of aphids or green fly on my plum tree. due to its height and size it would be near impossible to rub them off.

only moved here in October so don't now variety, but the new leaves coming thru are very curly. almost looks as if they're shriverling, but i'm asuming this is normal as the larger growth seems to open quite healthy

any suggestions?

thanks :)