One of the gardener's enemies that is seldom seen does most of its damage after dark. This enemy is slugs.

Slugs belong to the same group as snails, oysters and clams. Snails and slugs are similar to each other except that snails have a shell. Both secrete mucus, which helps them glide along.

Slugs require moisture to survive and therefore are most troublesome in the type of growing weather we are currently experiencing. When conditions are dry, they go dormant. They become active again when moisture is available.

Slugs feed on the leaves of a wide variety of plants and may completely devour young seedlings. Fruits lying on the ground, especially if shaded by the foliage, such as strawberries and tomatoes, are often attacked.

Since slugs feed only at night and on very cloudy days, gardeners seldom see them. However, they do leave their calling cards - the mucous which they glide along on dries and leaves a silvery trail.

Numerous methods have been devised to control slugs. The most common of these is the beer trap. Beer is placed in a shallow pan and set in the garden. Slugs are attracted to the beer and climb into the brew and drown. The addition of a teaspoon of sugar to the beer has been found to be even more effective.

A beer drinker who refused to share his beer with the slugs reasoned that the addition of sugar to the beer had a greater attraction than beer alone. Therefore sugar water alone might work. To the beer drinker's surprise, sugar water was most effective. Further research has shown that 1½ ounce of sugar added to 1 quart of water gave the optimum performance.

One word of caution when using beer or sugar water - your neighbor's slugs may join the party.

Organic gardeners use diatomaceous earth to control slugs. It is spread around the plants and its sharp particles prevent the slugs from gliding over it.

Researchers at Vermont University have discovered that slugs cannot cross over copper. If copper tubing, such as water pipes, are laid on the ground, the slugs will not cross it. To be effective the pipe must be in contact with the soil.

Gardeners with time to spare can control slugs by placing boards in the garden. Slugs hide under the boards because the areas are dark and moist. Each day the boards are lifted and the slow moving slugs are easy to destroy.

Weedy lawn areas adjacent to gardens are an ideal habitat for slugs as they feed on the weeds. Lawns that are weed-free are also slug-free.

The chemical control for slugs is metaldehyde. This material can be purchased as a liquid, granules or pellets. Typically it requires reapplication about every two weeks. Ohio State University researchers found metaldehyde the most reliable control.