While this is suggestive of wood decay, not all instances of wood decay doom a tree, fortunately, though they also cannot be cured or treated. Trees have ways of compartmentalizing decay internally, something that won't be detectable from a visual inspection of the trunk, but sometimes it works and sometimes it doesn't. Some fungi or wood-boring insects that contribute to wood decay attack seemingly-healthy trees, but the majority take advantages of existing injuries or stress (like from drought, girdling roots, or other factors) and are secondary issues.

We recommend that you have the tree evaluated by a certified arborist or licensed tree expert. While they cannot treat every condition, they can help to make a diagnosis, assess tree safety, and look for sources of tree stress that might be able to be alleviated. You can always get a second opinion before taking action (should any action be recommended) since few issues would require immediate intervention.

Miri