This type of injury is produced by an insect with piercing-sucking mouthparts, most likely Four-lined Plant Bugs, which feed from approximately late April into June. The damage they do is largely aesthetic in nature. Plants typically grow out of the damage later on in the season. Four-lined Plant Bugs have just one generation per year and they're almost finished feeding now. For this reason, we do not recommend any insecticidal treatments. You can read more about the on Ohio State's webpage.

Christa