In the Midwest they would cover an entire wall of your house on the sunny side. I put a lot of dawn in a hand held water bottle sprayer, just short of where the sprayer bottle would not spray if too much was added. Or where the water inside the bottle turned a medium orange from the dawn.
For me just one time application did the trick after seeing them.
Just a note don't let your pets get at them or eat them they have a toxic juice in them. Tastes bad so they do spit them out but then there are the determined dumb dogs that do keep eating them!
This also works on those Chinese biting lady bugs too.