The rest of the tree looks healthy. It’s not uncommon for trees to start looking like this after a few years. I don’t see any deep fissures or weeping sap. Nor do I see any borer holes. We haven’t had any deep freezes that could injure the tree. I’m no arborists so I could be wrong.
I think this is anthracnose canker. I get this pretty often in asian pear, certain other pear varieties, and in Betch rootstocks. One way I've treated it before is to bury the affected area or put a tube around the trunk and fill with soil. This seems to help a lot -- I don't know a magic spray for it but will follow to see if someone else does.
This will usually doom the tree as years go by - any branch or trunk that gets ringed will soon die. It is also pretty infectous over a 2-4 foot reach.