Thanks for writing. I don't usually recommend a one-size-fits-all-answer to insects --- some treatments work better on some insects than others. But a good starting place is a product called Captain Jack's Deadbug Brew; it's an organic, low-impact product that will kill many leaf-eating insects. You can spray it on the plant and it will harm insects as they eat the leaves. You can also use products containing neem oil or insecticidal soap --- both of these are also low-impact. But to work well, it's best to spray them directly on the insects.
Do you have a lot of flowering plants in your yard? If not, planting some can help attract beneficial insects, which will control the population of the pesty bugs for you. Beneficial insects will never completely eliminate the pests, but they will create a natural balance that allows good plant health.
One note: There's a common misperception that organic means something is safe. That's not necessarily true; there are synthetic chemicals that are actually safer to use around children/pets/etc than some organic products.
---Justin, Senior Garden Editor, BHG.com