 Next spring, you can spray liquid 28% or copper sulfate broadcast on bare soil, and this will help. In crop, if you're going to spray either 28% or copper sulfate, you need to use low rates and lots of water to reduce leaf burn. There are slug baits available with metalldehyde, but they're dangerous to humans and animals, so be careful if you use them. Finally, one of the biggest keys to overcoming slug challenges is to get the crop off to a quick start, so by the time slugs show up, your plants are too big for slugs to kill them.