I don't know because i am living in the tropics. The plant has a good structure. Maybe you can prune the top of the rotted branches.

Lorraine, I like to prune once my trees start into full growth in the Spring. Many will prune before.

Definitely prune any of the branch ends that look shriveled and/or rotting. Cut them back until the tissue is solid cream/white with not even a speck of beige in the cambium layer ( this is the thin layer in between the skin/bark and inner wood).

Rick