Suppose you used a tin can with both sides opened? I guess that wouldn’t work with a bush, unless you cut down the side with tin snips, and then duct taped it back together, perhaps. Or lined the cardboard with aluminum foil? Would either of those options work?
I believe these are climbing cut worms, since the damage is typically a foot above the ground. I have read that they ignore all such stuff around the base. I have only tried cardboard so far.
I’ll need to recon after dark around midnight to see if I can find whatever it is for sure.