Slugs and Snails
This article was originally published in The Dirt Doctor's Dirt Magazine, July 2003
If overnight newly planted seedlings are disappearing and there are large holes in your plants, the culprits are probably snails or slugs. Slugs and snails normally feed at night, and young garden seedlings and transplants are among their favorite meals. Healthy, promising seedlings can vanish overnight, and by the time you figure out what happened, the culprits have disappeared. Usually a close look at the plants will reveal the characteristic silvery trail. Snails and slugs are mollusks and need a moist environment to survive. They avoid the sun and come out mainly at night or on dark, cloudy days. They secrete mucous to move about and by using the same trail and sharing trails with other snails they save on mucous production. During cold or dry weather, snails can seal their shells, and remain dormant for several years. Typically, only 5% of the slug population is above ground at any given time. The other 95% is underground, digesting your seedlings, laying eggs, and often feeding on plant roots.
All chemical poison snail baits pose a serious danger to pets and children. When used properly accidents seldom occur, but pet or child poisonings can have serious consequences. Pets and children can be attracted to the fragrance, shape, size and color of snail baits. If you read these products today, you’ll notice the serious poison warnings that are now included on them. There is no need to use these potentially dangerous toxic products when there are many effective natural solutions to the problem.
Diatomaceous earth (DE) has been widely used for organic slug control, and can be effective. Some disadvantages are that you have to reapply it after rain and many times slugs can actually move directly through the product uninjured. And even so, the results are spotty. The heavy mucus they produce sometimes protects them from the (DE). A better option is a mixture of DE, hot pepper, and cedar flakes.
Other effective controls include garlic-pepper tea, which can be sprayed on plants that show damage. Beer or brewer’s yeast traps and always an effective way to lure your slugs and snails to their demise; simply place liquid in a shallow container, and sink into the soil. Bone meal or colloidal phosphate can be dusted in the infested area or dusted around specific plants. You can also encourage natural predators, like birds and turtles, to frequent your garden.
If you really have a serious problem with slugs and snails, you might want to consider another unlikely natural predator: the decollate snail. The decollate snail has been used in orange groves of citrus growers and in the gardens and landscapes throughout the temperate regions of the United States for nearly 150 years. This famous predator snail comes out of the leaf mulch or soil at night and eats the eggs of slugs and snails. It also feeds on the young snails. Another bonus is that they don’t feed on your garden plants. The decollate snail will feed on decaying leaf litter, decaying fruit and vegetables, but not actively growing plant material. The decollate snail lives for 2 years and lays a small amount of eggs on a regular basis so there should always be many new snail destroyers protecting your garden. When seen in the package they may look dry and inactive, but they will come to life when properly placed in your garden. Decollate snails pose no health threats to pets, birds or other mammals. Children may find them amusing to watch but not toxic if eaten.
Economic importance: Very destructive to many garden plants and food crops. The decollate snail is predatory and helps to control plant-eating snails, although there is some worry that it will destroy the balance of native snails--but we doubt it.
Natural control: Maintain permanent stands of clover and mulches to favor ground beetles and rove beetles (which eat slugs). Centipedes also eat slug eggs. Other predators include small mammals, snakes, frogs, toads, lizards, birds, and carnivorous beetles. In the insect world their biggest enemy is the larva of the lightning bug.
Organic control: Copper bands are supposed to work, but they sound like too much work to us. Dust dry hot pepper in problem areas--it works great. Mix with diatomaceous earth for economy. Coarse-textured, crushed hot pepper like as that used on pizza is best. Citrus oil spray works well, and coffee grounds. Broadcast coffee grounds around plants troubled by slugs and snails to run the pest off effectively. Use anywhere from 2 - 5 lbs of grounds per 1000 square feet.
Insight: Trapping can be done with banana peels, eaten grapefruit halves, apple cores, and beer or yeast water traps. Putting wood ashes or natural diatomaceous earth around plants helps repel snails and slugs. They all seem to be alcoholics--just one taste and they can't quit. Beer placed in a saucer or pan sunken to ground level will do them in.
Slugs and snails do have their good points. They help disperse seed and spores, break down organic matter, and keep down the population of other small pests. A big one called the decollate snail feeds on other snails.
The American Indians used them for food. Boiled or roasted snails were a staple in their diet.