Whatever might have caused the damage has likely moved/morphed on :-) These are not fresh wounds, but have scarred over to some extent as evidenced by the dry, brown edges. Seldom is insect damage such as this harmful to the health of the tree - it's more of a cosmetic thing that can or even should be overlooked. Often the treatment for these problems is more disruptive than the pest, as it can destroy beneficials and be harmful to natural predators (like birds) as well.

If this and the other issues continue to concern you, take a sample to your local extension office for diagnosis and recommended control. However, unless you can catch the insect culprit in the act, they may not be able to provide many specifics.