my apple tree has green fly what do i do to get rid
If it's a tree it's probably not going to be practical to do very much. They're unsightly, but they don't actually do much damage. If it's really covered, the tree may be weak, and you need to look for the reason.
You could spray the tree with an insecticide - but do try spraying just with water first, sometimes all you need to do is dislodge them and often they don't come back.