It's good to see the beetle, but at the level you describe, it probably won't get it under control. Here is Howard's page about treating scale
Have you looked into how the crape myrtles were planted? Are they too deep in the ground, do they get too much or too little water? To keep this from occurring again, you'll need to address how it was planted and how it is situated.
Meanwhile, you could try knocking them off with high water pressure and hope the beetles get the rest, but I suspect if the infestation is as bad as you say that you'll need to use the biowash and orange oil in water mix.