We’ve always had slugs, living in Houston they are just part of the outdoors. We also have dogs who eat outside and scatter their dog food around. This is prime slug bait, and inadvertently we have attracted every slug within miles to our back yard. They show up at night to eat the leftover bits of dog food in the grass that had been overlooked by the dogs or left out overnight. While this is unwise and is being remedied, the good side of it is that the slugs are not anywhere near the garden – yet. They are conveniently where the easy food is. This makes it easy for us to manually eliminate the ones we can see. I’m reluctant to use poisons or harsh chemical methods, so we are doing the water/ammonia mixture treatment so often touted by gardeners on the various forums. It works. It works well. 1 art ammonia to 4 or 5 parts water in a spray bottle was all it took. That mixture, sprayed on a slug, causes death almost immediately. It is also a cheap source of nitrogen for the plants, but be careful not to mix too strong a mixture and it is probably wise to go easy on it. We tried to keep the spray on the actual slug itself and didn’t ‘carpet bomb’ by saturating an area.

We hunted them last night eliminating over 100 slugs from our yard, and will go back nightly for a week. It is said that after a week of manually reducing the population, the problem is fairly under control. I hope so.

Here are some links on slug warefare.
Using Ammonia to kill Slugs
Controlling Slugs and Snails in Your Garden
Garden Slugs: Organic and Natural Slug Control
Ammonia Slug Control
Ugh…Slugs! & Snails too
How to get rid of garden slugs