"Billy" wrote in message

When you¹re down to only a few slugs, you can fall back on the
traditional organic control, which is to trap them with beer. Put an
inch or so of any beer in a cup, bury it in the garden nearly to the
rim, and collect your drowned slugs in the morning. Or, put some beer in
plastic drink bottles and lay them on their sides in the garden. The
slugs will crawl in and drown.

As I understand it, it's not drowning, it's the yeast. I'd always thought
that the yeast acts as a poison for slugs and snails so you dont' need huge
amounts of it. The dregs from the bottom of a bottle of beer that has been
drunk is enough. I've never used a lot of beer and still the snails have
died (and not whilst in the the liquid, but near it). Now you've got me
wondering about what it is about the beer and yeast spreads that works.