hi larry, sorry if i wasn’t clear. on the most affected branches, those dead leaves are covering that area of bark where the tree goes from living to dead. those are the parts that are going to be most diagnostic. now that the leaves are gone would be a great time to take another pic.
failing that, i suspect fireblight, which will require relatively drastic cuts to contain - which is why the more information we can get, the better for you and for your tree.