So they've been there for 3 1/2+ months causing that sort of damage?
"Recommended control method is use preventative insecticides (systemics) before infestations occur and to screen or isolate the plants. Infested plants should be isolated from the rest of plants."
If isolating them is impractical then use insecticides.
"Try Bayer Advanced Dual Action Rose and Plant Insect Killer which contains both a pyrethroid and Imidacloprid."
If they didn't go away back in May why didn't you use an insecticide then?
The pyrethroid Beta-cyfluthrin is very effective against the nymphs. Imidiacloprid is a systemic. The Bayer Advanced has both as active ingredients and is generally safe to use on most CPs.
If they went away back in May and came back then you need to use a systemic between infestations.
It would probably help to spray any yard plants with a garden sprayer too. If you live in an apartment or with some other shared garden space this could be a problem.
Grand Hotel... always the same. People come, people go. Nothing ever happens.