Slugs and snails are mollusks that are related to clams, oysters, and other shellfish. Snails have coiled shells on their backs for protection from predators. Slugs have a soft shell that is hidden underneath their fleshy mantle. Both creatures leave slimy trails of mucus wherever they travel. The slime allows them to slide over various surfaces and these slime trails serve as markers to and from food and hiding areas. Adults lay eggs, which are clear, rounded or oval, in jelly-like masses in moist, dark areas. Snails require up to two years to mature. Most slug species mature more quickly. Both feed on a wide variety of garden plants, including vegetables, fruit, and ornamentals. They can devour a small seedling or whole leaf in one night.
Like all mollusks, slugs and snails do not survive in direct sunlight or dry heat. They require moist or wet environments. Consequently, they do most of their work at night or during periods of high humidity or rainfall. During the heat of the day, they hide in damp places under boards or rocks, in crevices, and in thick ground covers. While slugs and snails have natural predators such as birds, snakes, toads, and beetles, they are such prolific breeders that natural predators cannot keep up with their numbers.
Control of these pests include a wide variety of techniques, such as folk remedies, chemicals, and cultural methods. In fact, many gardeners have developed their own tried and true methods of ridding their gardens of these mollusks.
Physical Removal: Since slugs and snails are slow moving, they can easily be picked off plants early in the morning, after dark, or during times of high humidity or rain. For the faint of heart, use thin latex gloves or tweezers to remove them. After removing the critters, drop them into a bucket of soapy water or squash them (some sources suggest that squashing them on the ground simply attracts more of the pests to the same area).
Habitat Modification: Removing their hiding places is a good way to control the pests. Remove old boards, rock piles, and other debris to eliminate or restrict their habitats. One technique for getting rid of the critters is to leave a piece of wood, orange peel, or other material on the ground to provide a hiding place for the pests. In the morning when the mollusks have retreated from the heat, the wood or material can be picked up and the creatures can be disposed of or smashed.
Barriers: Copper tubing or thin sheets of copper seem to repel the pests. A chemical or toxic reaction occurs when they come in contact with the copper. Other barriers include crushed eggshells, ground limestone, powdered ginger, sawdust, or other rough barriers to keep the slimy ones from crossing the area to their feeding grounds.
Non-Chemical Solutions: A sprinkling of salt, vinegar, boiling water, or a soapy solution on the slugs and snails will kill them, but you may not want some of these products in your garden soil or on plants. Diatomaceous earth (a silica product) damages the protective coat of slugs and snails. A little beer or fermented yeast concoction, put in a shallow container attracts the pests and they drown after imbibing the liquid. Some gardeners indicate that some beer brands work better than others. You be the judge.
Chemical Controls: Commercially available slug and snail baits are very effective control methods. They are sold in the form of granules, pellets, powders, or liquids. The effective ingredient in these controls is metaldehyde or methiocarb, which cause death by dehydration and works quickly. Care must be taken, however, to keep the chemicals away from the children, pets, birds, and wildlife.