One of the many leaf sucking insects but it is minor damage and nothing to be overly concerned about at this point. Flea beetles is a possibility as it is that time for them in parts of the country right now (which is why you need to include your location in your posts). If it is them you can brush your hands over the leaves and see tiny black leaping/hopping beetles.

Dave

Not a sucking pest. One that chews. Only the green surface was eaten and very little of that. If you see more, look top side and reverse for something small.

Flea Beetles is my guess. I have seen lots of flea beetle damage when I worked at the wholesale nursery in Texas.