?Plum leaf curling aphid? Unroll a leaf and look inside of it, the aphid chews the veins on the backs of the leaves to curl it over as protection.

Thanks very much, it would appear that that is the problem. Any cure or treatment you can advise

They actually do not do that much harm to the tree, they just make it look odd. Spraying with an insecticide of your choice is the only option, but you do have to spray inside the leaf and it still will stay rolled up. We ignore it to a large extent on our trees.

Again thank you very much I will take your advice.

Cheers

Terry

Hi there,
Re curly leaf disese. It's damp-borne virus, remove leaves and cover in damp weather. I think it does harm trees with a lot of damaged leaves.So, probably worth the effort.You are not doing anything wrong in you maintenance! Don't prune in winter, do this in summer, LIGHTLY like trimming hair!

By the way, Insecticide is a BAD idea. Its not an insect, its a virus, present in the air, and plums are happier in dry, hot environments generally because of this.
Similarly, with silver leaf disease which is present in winter and can kill trees very quickly if you prune/ damage prunus species in winter