What is this?
A neat, horizontal or vertical line of holes in a tree is Sapsucker (a woodpecker) damage. If intense enough, this damage can girdle and kill the tree.
How do I fix it?
If the damage is not too significant, the tree will seal itself. If the damage is excessive, the tree may need to be removed. For help evaluating your tree call the NJ Tree Foundation or a licensed tree expert. Take immediate steps to prevent more damage, as explained in the next answer.
Can it be prevented in the future?
Try hanging shiny or noisy objects from the tree – old CDs, long strips of foil or foil take-out containers. There are also commercial substances that help deter Sapsucker damage.