Has anyone ever seen this? This is a representative sample of the condition of the majority of roof sheathing. It looks like bores, as if created by small insects, but is very evenly distributed and no signs of insect parts could be seen anywhere in the vicinity.
A few sheets of sheathing are not affected at all; suspect they were replacements during the last re-roof approx 20 years ago. Also suspect the affected sheathing to be original (38 years old) and free of any fire retardant, increasing my suspicion of insect activity.