Noticed this large brown spot on large oak trunk. There is a hole at the top of the spot which is soft. The brown area below the hole is still solid. There does not appear to be any other singular symptom to note... a couple yellowing leaves maybe. ?
Kent County Michigan
A nice tree! This appears to be a canker perhaps the early stages of hypoxylon canker. This could also be beginning of bacterial wetwood/slime flux. Getting a diagnosis from a certified arborist would be advised. Check out the following links:
I hope this helps,