In many parts of the country, slugs and snails are one of the most vexing garden pests. They are similar creatures (slugs are merely snails without shells) and feed on many ornamental plants, vegetables, and flowers by chewing tissue with their rasping mouth parts; they leave telltale silvery slime trails as they glide along. They are a major problem for citrus trees.
Shiny black ground beetles eat some snail and slug eggs. Handpicking is an effective way to reduce adult populations. To speed up the process, attract the pests to a certain spot in the garden by placing a slightly elevated board there; they'll congregate in the cool shade on the bottom of the board, ready for fast and easy disposal. Some gardeners set traps containing stale beer slightly below ground level; the pests are drawn to the beer, crawl into the traps, and drown.
To protect citrus and other trees, encircle the trunks with a 4-inch-wide band of copper stripping; slugs and snails won't crawl over it. You can also set copper strips in the ground vertically to form a sort of fence around valuable plants or an entire bed, or surround plants or beds with 4- to 5-inch-wide sawdust "moats" (such sawdust rings are less effective in wet weather and rainy climates).
Chemical controls include bait or meal containing metaldehyde or methiocarb. Be careful with such controls if children or pets use the garden, since bait is attractive to them.