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Marin IJ Articles

How to keep snails, slugs away

  • Nanette Londeree
  • If you grow plants, it’s likely you don’t need an introduction to snails and slugs, the bane to most gardeners. Damage from these creeping thugs is estimated to cost the state of California millions of dollars every year. Loosely related to octopi and oysters, they glide along on their muscular foot, secreting mucus to facilitate movement, leaving their trademark glistening trail behind.

    With similar biology, the snail carries an external shell while slugs have evolved without one. Both are most active at night or on foggy, cloudy days. During cold weather, they hibernate in topsoil, while during hot, dry weather, snails can seal themselves off with a parchment-like membrane, and become dormant for up to four years. As each individual is equipped with both male and female reproductive organs, under desirable conditions, their numbers can explode.

    The mouths of these little garden pigs sport rows of sharp “teeth” that tear plant tissue, so that damage may appear scraped, shredded or just gone. With insatiable appetites, they can eat double their body weight in a day. And, as each individual is equipped with both male and female reproductive organs, under desirable conditions, their numbers can explode.

    Snails and slugs love to eat plants with tender foliage and fruit. Favorites include seedlings and plants with succulent foliage; they seriously damage basil, beans, cabbage, lettuce and many other vegetable plants along with dahlia, delphinium, hosta and marigold. Ripening fruits close to the ground like strawberries are easy targets. And they’ll climb trees to feed on foliage and fruit, especially citrus.

    Successfully managing these creatures takes a multipronged approach, beginning with plant selection — choose types they’re generally not interested in, like begonias, California poppy, fuchsias, geraniums, impatiens and lantana. They avoid many plants with stiff leaves and highly scented foliage like lavender, rosemary and sage, along with most ornamental grasses and woody plants.

    Change the environment and make it less hospitable. Snails and slugs thrive in moist, decaying plant matter; remove debris and potential hiding places. Alter the surface to make it difficult for them to travel; try gravel, crushed eggshells, coarse sand or wood chips. Diatomaceous earth has edges that are sharp and jagged that can lacerate these soft-bodied pests causing them to dehydrate.

    Copper barriers can keep them at bay; when they come into contact with the metal, they get something like an electric shock. Wrap copper foil around container plants and tree trunks; they won’t cross it. For raised beds, use 4- to 6-inch bands of copper, buried an inch below the soil surface and bent at the top to keep these varmints out.

    Provide desirable habitat for the many predators of snails and slugs; toads, frogs, garter snakes and salamanders along with birds and opossums love them.

    If you’re out early in the morning, hand pick and destroy them. Or trap them; lay out some boards, flower pots or inverted melon rinds in areas they might inhabit, raised off an inch or so off the ground. Check daily and scrape off the accumulated catch. There are also commercially available traps that may use sugar water or beer as an attractant.

    Probably the most popular method of managing snails is to bait them with a poison. While it’s a quick and easy way to eliminate them, it’s risky. The majority of baits contain metaldehyde which is highly poisonous to dogs and cats. The molasses or brown sugar added to the bait is attractive to snails and slugs and dogs and cats. Don’t use metaldehyde snail baits where children and pets could encounter them.

    Effective products are available that are toxic to the pests and can be safely used around pets, humans, fish, birds, beneficial insects and mammals; they contain iron phosphate, a compound found naturally in the soil. If it’s not consumed by the snails or slugs, it will break down in the soil.

    With a little planning and a lot of diligence, you can keep these common garden nuisances at a tolerable level.