Gardening Articles: Care :: Pests & Problems
Snails and Slugs
by David George Gordon
Adult slugs range in size from 1/2" to 10" depending on the species.
No garden pest elicits a more visceral response than the lowly slug. And its cousin, the snail, equally capable of destruction of prized vegetables and flowers, is only partially redeemed by its reputation among gourmets. You'll never be able to eliminate all of the snails and slugs in your garden as proved by one English zoologist who removed 400 slugs from a quarter-acre garden each night for several years with no observable effect on the population. And as snails and slugs are basically small cogs in nature's big machine, there are many good reasons why you shouldn't even try. The challenge for most gardeners is to maintain a balance.
The more familiar you are with slugs' and snails' patterns for raiding your garden, the more capable you will be of limiting damage to your plants. You're most likely to find garden snails and slugs during months with moderate but consistent rainfall and nighttime temperatures above 50°F. And, with a few exceptions, they are most active at night. Go into your garden after dark or shortly before sunrise, armed with a flashlight or, better yet, a headlamp, which will leave both hands free. Look for large, irregularly shaped holes in the leaves of your plants and telltale slime trails. Periodically conduct these informal surveys of slug populations and then try the most humane and least environmentally damaging control measures first.
Begin by Altering the Environment
The first step is making your property less desirable for these creatures. This can involve choosing plants such as rhododendrons and other hard-leaved evergreens that slugs and snails will ignore and avoiding those that they actively seek. Both snails and slugs feast on most plants, especially young, tender transplants, leafy vegetables and succulent plant parts. Slugs particularly love Campanula carpatica, Chinese cabbage, daffodil, delphinium, leopard's bane (Doronicum), gentian, horseradish, hosta, lettuce, lilies, mustard greens, perennial lobelia, marigolds, primroses, strawberries, Trillium, tuberous begonias and Viola.
Keep the garden clear of debris that offers cool, dark, moist, hiding places and don't overwater. Dense ground covers of ivy and succulents are notorious snail and slug havens. Avoid mulching, or wait until the plants are well established or the temperature is over 70°F. Cultivate frequently to destroy snail and slug eggs before they hatch.
Ground beetles, garter snakes, moles and shrews all prey on slugs. You can also invite slug-eating predators into your yard. Unsupervised chickens, geese and ducks sometimes cause more damage to plants than the slugs do, however. In some regions, you can rely upon the decollate snail (Ruminia decollata), a snail that prefers to eat snails and slugs over vegetation. They are available from some biological control suppliers.
Mount a Snail and Slug Safari
Hand-picking snails and slugs from your plants can be an effective control. If you're squeamish about slime, wear rubber gloves or use a long-handled dandelion digger or a pair of long tweezers. Plop any captives into a jar (filled with soapy water so they don't crawl out) and use a screw top, as they have been known to push with sufficient force to pop the lid off of a yogurt container.