Lines of little holes in oak bark
 

Hello all

Just this week, on a red oak,
about ten years old, trunk girth about 25 - 30 cm,
and apparently otherwise strong and healthy,
I noticed a lot of little holes
arranged in very neat, horizontal lines
around the trunk.

What are these ? Are they insect holes ?
Are they a threat to the host ?
Any suggestions ?

Best regards and thanks in advance from
Ray
PS - This is in Alsace, France