Do those beetles have a natural predator? They are hard bodied, so many insect sprays don't really work on them. Japanese beetles (JB) love our American roses. Birds are our best hedge against the JB, maybe they like your beetles too! Lovely photo!
@louannwarren Thanks Lou Ann, as cute as they are, they are horrific! Unfortunately none of our birds like them. All that helps is a certain spray mixture I get from a garden centre