Last Summer ants farmed aphids on the new growth of ny fruiting cherry tree.This has resulted in stunted growth at the end of all branches - multiple buds on consrticted stems. Should I prune this out. if so when and how ?
Don't prune now, as cherries bleed profusely. You should wait until summer, when growth has matured.
This year, take steps to prevent the ants farming aphids again, and remove aphids when you see them. One method is a broad strip of vaseline near the base of the tree to stop ants climbiing it.