I have two mature Satsumas and another I planted several years ago. One of the mature trees has developed some kind of bark disease and I would appreciate some input on what may have caused it and if I should do anything now or if the damage is done and the tree is now in the healing stage.

Here is the tree (in the foreground) in its general surroundings. It has a nice full canopy of healthy leaves. It produced heavily last year but only has a few fruitlets this year. Same goes for the other Satsuma in the background on the right.

Here is the north side of the trunk showing an area about the size of the palm of your hand where the bark has peeled off and is still peeling.

Here is a closeup

There is a little bit of sap dripping down the trunk but I don't see any signs of trauma,,,,woodpecker damage for example. If I had to guess, I would say there was a fungal infection during the spring when it was much wetter and now that area has died and is peeling off. Any other ideas? Should I leave it alone and let the tree heal on its own or is there something I should treat it with? I assume this will ultimately lead to rot into the heartwood if the bark heals around the damage.

Thanks for y'all's input!

John