Get a bowl of water and knock or toss the JB’s into the water. They’ll drown in a few seconds. You can add a drop of dish washing liquid if you’d like. Their body structure sticks their face under water. It’s quick and easy, no nasty chemicals or stinky bag traps.
At some point the size of the garden or the height of the plants preclude daily beetle drowning (better twice daily.) I have reached that point.
And I have plots at a community garden that I don’t visit daily.
So I am doing the experiment next year, having seen good results locally. But I am interested in the experience of other gardeners on this thread.
IME the JBs don’t drown quickly. They cluster up in a raft, and try to climb out on top of each other. They’ll chain up like the barrel of monkeys game.
But at least the water mostly keeps them from flying off. Then I pour them out onto a flat stone and crush them. For a few days the ants would clean off the stone, and then they got tired of JB.
I’ve got lots of birds. They never eat the JBs.
Once I spent half an hour trying to feed a JB to a praying mantis. Finally annoyed it enough to stab the beetle - it took one taste and shook its claw violently to dislodge the beetle.
They must have some protective chemical but they don’t smell noxious.