Little harm to tree.  Damage to the veneer

The arrows point to the tracks of the cambium miners.

You see three growth increments in a cross section or as we call it "Transverse".

Here we see 3 increments - 1-3.  As that increment was growing and the cambium zone was located in that spatial position, the Miners swam through, in a sense leaving these markings.  They went through as the tree was going from spring wood to summer wood.  1-3 are cambium miners tracks.  Not harmful to the single tree or the system.

Image source (SHIGO 2002)

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