Thank you for the excellent image which clearly displays a box elder bug nymph (youngster).
Although I haven't seen any official reports from the entomologists (insect specialists), they seem to be more numerous than during recent years.
It's very likely they're simply congregating on the plants, not damaging them. Their normal food consists of maple seeds.
A harsh water spray may help to discourage them so that they'll leave.
Or you might try insecticidal soap, diluted according to label directions. Do not use if the temperature is 80F or higher because it's likely the spray will damage the plants.