Slugs can devastate a beautiful Hosta collection and reduce a moist shade garden to tatters. FIGHT BACK! Mix a simple solution of 20% household ammonia (1 part ammonia to 4 parts water). Using a watering can apply this solution generously as a  soil soak around the crown of your Hosta plants just as the pips are breaking the soil in the spring. This solution will kill overwintering slugs and slug eggs in the soil. We have found that it significantly reduces slug populations.
Note: Once the Hostas have leafed out a milder 10% solution can be applied during the growing season.