Northern California is home to some enormous slugs. The local banana slug is the second largest species in the world, growing up to 250 mm (10 inches) long. This slug is so large that it gets into home through doggie doors and open windows.
Coastal Northern California residents often feel the squish of slugs under their feet as they go to the bathroom at night. In the morning, they may find enormous banana slugs hiding in the folds of their clothing. Slugs leave trails of slime on floors, walls, and kitchen tables.
Residents of Northern California deal with their slug problems in creative ways. Russian River residents sometimes host annual slug races, drawing the ire of animal rights activists. The races themselves are predictably slow going, with some slugs slithering in the wrong direction and, inevitably, some of the contestants choosing to mate with each other.
Centuries of Northern Californians have eaten slugs as food. Native American tribes of the American and Canadian Pacific coasts fought off famine by eating dried or smoked slugs. Early German settlers gutted and pounded out banana slugs, frying them to make slug braten. Russian River even hosted an annual festival of slug cuisine. As part of “An Event to Make Everyone Vegetarian,” slug dishes were paired with local Sonoma county wines, which the judges drank before tasting the slugs.
Coastal California is also home to enormous brown snails, brought to North America from France and Italy to be raised as food. Some Californians have adapted to their snail infestations by raising them as escargot and for snail caviar. Most of us, of course, find snails and slugs to be an acquired taste.
If you don’t live in Northern California, and probably even if you do, chances are that you don’t to learn how to live with (or eat) your slugs and snails. You just want them to go. But you don’t have to result to cooking these slimy pests to get rid of them naturally. First let’s take a look at some natural methods that sometimes work and sometimes don’t.
1. Let Slugs and Snails Control Themselves
We don’t usually think of slugs and snails as creatures that get sick, but they actually are susceptible to many kinds of bacterial, viral, and parasitic infections of their own. If you see a snail with a misshaped shell, chances are that it has a bacterial infection. Snails that are active during the day often have infections with a kind of parasite known as a trematode. The trematode multiplies inside the snail, and then changes the snail’s sense of day and night so it is more likely to be eaten by birds that will in turn spread the parasite.
Just as your plants can be infested by mites during dry, warm weather, mites can attack both snails and slugs. Snails and slugs can attract fungal infections. There is even a parasitic nematode that infects the eye stalks of slugs so that they become large, orange, glowing orbs that attract birds that eat the slug and spread the parasite’s eggs.
Scientists estimate that 20 to 100% of all the snails and slugs in garden settings have infections. If you see a diseased snail or slug, especially if you have a serious snail or slug infestation, don’t get in a hurry to kill it. Let nature take its course.
2. Let Other Animals Control Your Slugs and Snails
An astonishing range of animals large and small feed on snails and slugs. Hedgehogs, shrews, and field mice are the biggest consumers of snails and slugs. Hedgehogs are especially attracted to snails. In other parts of the world, snails and slugs are consumed by birds, foxes, pigs, rats, snakes, and even rabbits (which eat more meat than most of us would expect). In the United States, about ¾ of brown garden snails are eventually eaten by rats. The rats pick up parasites from the snails, so the two kinds of pests control each other. Slugs and snails are also eaten by beetles, notably by a species known in the UK as glow worms and in the US as lightning bugs. They are also consumed by ants, flies, and leeches.
Sometimes you have to choose your pest. Or you can let one pest problem take care of another, just waiting a little while with some of your eradication efforts.
3. Diatomaceous Earth, Eggshells, and Other Gritty Barriers
Walking through the garden, sprinkling powdery diatomaceous earth (available from the garden shop) or crushed egg shells, soot or sawdust as you go is one way to slow down the movement of snails and slugs. Any finely powdered substance with tiny sharp edges will irritate slugs and snails. When food is abundant, slugs and snails won’t cross diatomaceous earth, but when they are hungry, they will cross it.
Why don’t diatomaceous earth and other powdery barriers always work? These tiny creeping creatures don’t actually touch the ground as they travel across it. They float on slime. That’s the reason you see a slime trail where snails and slugs have passed. They secrete slime and pull themselves across a smooth surface of their own making. Snails and slugs can modify the viscosity (stickiness) of their mucus to protect themselves from sharp edges. If the barrier is not at least 75 mm (3 inches) across, 25 mm (1 inch) high, and composed of dry grit, the snail or slug will
Defeating gritty barriers comes at a cost, however. For every meter a slug or snail travels, it loses about 1% of its body weight. The more mucus it has to produce, the more easily it can succumb to dryness. Diatomaceous earth and other gritty barriers will work best in dry weather, and are almost totally ineffective when it rains.
4. Copper Barriers
A strip of copper such as Snail-Barr around your planting beds or at the base of trees or shrubs offers good protection against snails and slugs for several years if it is applied correctly.
- Vertical copper screens need to be at least 100 mm (4 inches) tall, with about half of the screen buried beneath the surface of the soil so snails and slugs won’t burrow under it.
- Copper trunk protectors need to be cut with a 200 mm (8 inch) overlap to leave room for trees to grow. They are attached with a single staple at middle of the roll, the tabs pulled so they are at a 90 degree angle to the trunk.
- Copper bars around raised beds and planting boxes only work if the soil is snail- and slug-free before they are put in place. Solarizing the soil (covering it with a black tarp and letting it heat in the sun) is a good way to kill their eggs before planting.
Bordeaux mixture (a combination of copper sulfate and lime, the mineral) can be painted onto the base of tree trunks to protect against snails and slugs for up to two years. Covering the Bordeaux mixture with a layer of latex paint will make it last longer.
5. How does copper work?
Copper drives the immune system’s inflammatory response to infection. Feeding on dead leaves, dog poo, rotting wood, and dead insects along with your prized plants, slugs and snails are exposed to an enormous number of potentially deadly pathogens. Copper, as a nutrient, power their immune systems to fight the infections they encounter in their environment that otherwise would kill them. Direct contact with copper, however, triggers an immediate immune response that the slug or snail finds painful, so it changes its path.
6. Coffee and Coffee Grounds
Snails move at, well, a snail’s pace. Slugs are sluggish. The last thing a snail or slug wants is to get caffeine jitters. The nerves that control motion in these animals are especially sensitive to caffeine. It causes calcium to flow into muscle cells to make them contract, so that the slug or snail cannot move forward. It pulls itself back from the caffeine source.
It only takes a 0.01% caffeine solution (that’s about 1/5 as much caffeine as is found in brewed tea or instant coffee) to repel slugs. A 1% solution of caffeine, which would be something you could make by grinding up a No-Doze tablet into a cup of water, is fatal to them. Coffee grounds and spent loose tea are just an irritation. They won’t kill slugs or snails. But coffee grounds won’t kill beneficial insects or frogs, either, and they are a better barrier for protecting small areas of your garden. Coffee grounds and caffeine drenches most useful for protecting potted plants.
7. Slug Pubs
Slugs and snails are tiny alcoholics, common wisdom tells us. Put out beer in a deep container with its lip at ground level, and the beer guzzling pests will first take a swim and then drown.
The truth is, beer traps are modestly effective against slugs and seldom effective at all against snails. Here’s what you need to know:
- Slugs and snails are attracted to yeast, not alcohol. Budweiser is especially tasty to slugs and snails.
- Most slugs and snails are able to climb out of their beer bath. Maybe they get a hangover the next day and leave your plants alone, but beer usually does not kill them.
- A combination of sugar and yeast works just as well as beer.
- Beer traps catch smaller slugs. Maybe it’s because they are underage.
If you are planning to control slugs with beer, you will need to put out a trap about every 2 meters (6 feet) in every direction throughout the area you plan to protect. Tuna fish cans are a useful container, just large enough to trap slugs and just small enough that the scent of the beer is easily detected. Saucers also work for smaller pests.
Controlling slugs and snails by collecting them by hand is tedious but effective. At first, you will need to do it every night.
Draw out slugs and snails by watering the ground around your plants late in the afternoon. After sunset, go out into your garden with a flashlight and look for infestations near tender growth, under leaves, and on plants surrounded by decaying leaves or compost. You can dispose of the snails and slugs you collect in the trash or you can put them in your compost pile as noted below.
In addition, you could also try these methods
- Don’t bother with cornmeal, oat bran, or other fiber foods to make slugs and snails “explode” by feeding them. Snails are fed meal to clean their digestive tracts before they are eaten as escargot. They eat higher-fiber foods as part of their regular diet.
- Start growing carnivorous plants. A Dutch triffid has been bred specifically to eat slugs.
- Use plants slugs and snails don’t like at the edges of your garden, and give plants they find especially tasty extra protection. Pest-resistant perennials include astilbe, dianthus, columbine, catnip, peony, creeping phlox, meadow rue, and contrary to conventional wisdom, hostas. Hydrangeas and roses are slug-resistant because of fuzzy leaves and thorny stems. Slugs like most other tender plants, so mix tender annuals and resistant perennials to slow them down.
- Spray plants with a diluted mixture of essential oils of thyme or horehound (Marrubium vulgare), 1 drop of oil in 1 cup of water, late in the evening to deter to slugs.
- Eucalyptus oil deters snails.
- Pomegranate peels around the base of plants also stop snails.
- Don’t try to kill slugs by pouring salt on them. Larger slugs will survive by generating lots of slime, making them impossible to pick up. The salt won’t kill the slug, but will kill some of your plants.
- Don’t just smash snails and slugs and leave them on the ground. Their dead bodies can transmit parasitic nematodes to your pets.
- Prune the tips of shrubs that touch the ground to stop them from becoming a slug and snail highway.
- Keep the edges of your lawn trimmed. This deprives slimy pests of daytime cover.
- Remove decaying matter from your garden, but don’t throw it away. Use it to make compost.
- If you have outdoor cats and dogs, don’t leave their food bowls near the garden. Slugs love pet food. Alternatively, use dog or cat food to lure slugs away from your garden.
- Cultivate your garden during cold weather. Turning the soil will expose slugs and snails to the cold and kill them.
- Introduce birds to your garden. Chickens, peacocks, and other birds will feed on snails and slugs you don’t even see.
- Place potted plants on blocks rather than directly on the ground.
- Place garden sheds on blocks so they do not become a winter home for slugs and snails.
- Soak vermiculite in water to make a mound around the base of your plants. Slugs and snails won’t be able to climb it, as long as the vermiculite is moist.
- Trap and release. Place half of an eaten grapefruit or the outer leaves of cabbage or lettuce in some part of your garden that has been attacked by slugs or snails. Let them congregate under the shelter you provide and relocate them to a safe place.
But where should you relocate slugs and snails?
A good place for them is the compost heap. Live snails and slugs are a useful addition to the compost bin. They feed on decaying plant matter, so they will never leave your compost. (Just be sure it is well cured, having generated heat, before you spread it over your garden.) They break down paper, bark, and peelings to make nitrogen-rich manure. Dead slugs will be eaten by living slugs. And the finished product will give your plants more strength to fight off garden pests.