Beetles of several types eat the leaves. Flea beetle chews small shotholes in the leaves.
Mites cause yellowed foliage.
The insects are so small they are usually not noticed. Slugs eat the leaves at night and leave slime trails on the leaves. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information becomes public property upon publication and may be printed verbatim with credit to MSU Extension.