Okay, this is a little ridiculous, but it works. Bury a shallow container (like a yogurt pot) so the rim is level with the soil. Fill it with beer—any cheap lager will do. Woodlice are oddly attracted to the yeast smell.
They’ll crawl in for a sip, then drown in a boozy stupor. It’s a bit grim, I admit. Empty the trap every morning (glove up again) and refill. Just don’t use your favorite craft IPA; that would be a waste of good beer.
