Boards, bark, or other materials not less than six inches square make effective traps when placed in gardens. Each morning you can gather the slugs from under the traps and destroy them. An hour spent hand-picking and destroying slugs can noticeably reduce the population. Slugs can be kept from potted plants by placing the pots on boards or other supports over water in a pan. Alternatively, wrapping stems with cotton batting may keep slugs off plants.
Toads are slugs' most important natural enemy.
Many people claim that several ducks keeps a garden slug free. Slugs are attracted to and drown in a shallow dishes containing beer or baker's yeast dissolved in water. Set the top edges of the dish at ground level and cover loosely with a board so slugs can easily get into the mixture. Metaldehyde bait is the only chemical currently registered for use in controlling slugs in vegetable gardens. Check the label to determine whether the bait can be placed in the garden or only along the edges.