Besides welcoming you to this site, Darren, I want to thank you for not automatically assuming you have to kill a bug just because it does some damage.
It is a wise man that considers all options before he acts.
There are several beetles that eat bean foliage, but to my knowledge none eat in a pattern like this, which is typical for slugs and snails. In this case, however, I think I would put out some of the iron phosphate pellets mentioned above. The one I've used is just called "Slug and Snail Bait" by Schultz., and I'm there are more companies that make it, too.
