Answer: Based on your description I am not certain what is bothering your plants, however it is time for the metallic colored Japanese beetles to appear for the year and they will eat foliage as well as damage flowers on a wide variety of plants. Sometimes they can be repelled using a spray containing neem, but they are difficult to control as they fly very long distances. Carbaryl (the ingredient in Sevin) will kill the beetles it contacts, but has no residual action so its usefulness is a bit limited.
On your hostas, you might be having trouble with slugs. These are nocturnal so you would not see them but you might notice their silvery trails. These can be caught in slug traps using stale beer or baited using an iron-phosphate based product such as Sluggo, or you can sprinkle diatomaceous earth on the soil surface around the plants.
It is important to get a firm identification of the pest before you try to treat for it. Your local county extension may be aware of local infestations and can help you identify the insects. Based on knowing that, they can recommend the best control measures. Contact information inlcuding a toll free number is available at their web site at
I hope this helps!
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