Or sapsuckers...I did look at the trunk closely. I could not find anything resembling cankers, or matching those on a few forestry websites I looked at. I did see a fair number of circular holes on the trunk. I tried to peel away the bark to check for tunneling, but its almost impossible with that chunky, flaky bark. Maybe the holes just woodpeckers?
Id look for sooty mold as possible indication of micro insects mites cant always be seen with naked eye a paper test helps with some