The key to solving the slug problem in timing. Most yardeners wait until late August or early September when the slugs are absolutely decimating the hostas and any other plant they favor. By that time you have at least three generations of slugs in your yard. No wonder they do visible damage, there may be as many as 30 slugs per square foot in areas of their favorite food!
Start Early In Season
No matter which solution we offer here you select, it is best to get started dispatching slugs in the early spring when they emerge from the eggs that were laid last fall. The time to start hitting slugs is when you see the first sign of hostas breaking the soil surface in early spring. That is the time to start. Hit them again in a month and then again in early August.
When you get the slug population down to within reasonable limits, their natual predators - birds, toads, and ground beetles - will keep the numbers down each year so you don't see any more slug damage. It may take two seasons of diligent effort to achieve such a delightful condition in your yard.