What is causing small holes in the bark of my black walnut trees?
I have several black walnut trees. One of them has some small pieces of bark removed from the lower portion of the trunk. It appears that the bark is not removed enough to expose the wood underneath. The removed pieces litter the ground below the tree. In many of the places described there is a small hole that goes further into the bark. The holes are no bigger than one could make with a small nail. My next-door neighbor has two black walnut with the same issue. What causes this? Are these trees in danger, and is there anything we can do to combat this?
The first thing that comes to mind is wood boring insect(s), but without further information it is really hard to say. Do you see any insects? You mention holes. How is the tree doing overall? Do you notice any signs of damage to the canopy? If you could supply more information, it would be helpful.
Three photos are attached. I don't see any insects. This is the first year that we had this issue. This tree has been making fewer and fewer green leaves each year but the leaves it has had looked green and healthy. Some limbs in past years decayed and fell. I don't know how old it is but I think it may be at the end of its life. I'm mainly concerned about healthy Black Walnuts nearby that have not presented this condition.
I searched the literature looking for black walnut diseases, and didn't see any trunk borers, yet the holes look like insect damage. It could even be something laying eggs in the holes. Your Bureau of Forestry Service ranger in Blair county is Christopher Jones at 814-472-1862. I would call him and see if he can come out and look at your trees, or tell you who will.