Silver leaf is a fungal disease of the wood and leaves of some trees, especially plums, apples, apricots and cherries. The fungus infects the wood through wounds and causes a silvering of the leaves followed by death of the branch.
The treatment for Silver Leaf is simple but brutal. All infected wood needs to be cut back to healthy wood - about 3cm / 1in further than marks in the wood. All prunings should be burnt to avoid re-infecting the tree and other nearby plants.
Personally I would wait and see if the branch actually dies. We had Plum trees which always looked to have silvery leaves, but none of the branches died back.