Slugs and snails are common garden pests that can cause damage to a wide range of plants, from vegetables and fruits to flowers and ornamental plants. They voraciously feed on the tender leaves, buds, fruits, and stems, leaving behind holes and discolored patches. A large infestation can absolutely devastate your garden.
- Snail and Slug Basics
- Cultural Controls
- Physical Controls
- Bread Dough Slug and Snail Trap
- Biological Controls
- Chemical Controls
- What Doesn't Work to Control Snails – Common Myths
Snail and Slug Basics
Slugs and snails are not insects; they are soft-bodied mollusks. The main difference between slugs and snails is that the latter have a shell which is made mostly of calcium carbonate, like egg shells.
Also called gastropods, which means “stomach-foot”, snails and slugs travel on one “foot”, and leave a tell-tale trail of shiny, slimy mucus wherever they go. In fact, it is the presence of this slime that can help you distinguish slug and snail damage from that caused by other pests.
Slugs and snails are hermaphroditic, meaning each individual has both male and female reproductive organs. This means they are able to reproduce quickly and prolifically, and as a result do lots of damage if you don’t control their populations.
The best approach to slug and snail control is to use an integrated combination of cultural, physical and biological methods together. Here are 13 different methods to help you control slugs and snails naturally in your garden.
The way you cultivate and maintain your garden can have a big impact on preventing pest populations.
Reduce Slug and Snail Habitat
Slugs and snails feed mainly at night, so during the day they hide in moist, dark places under leaves, pots, planters, thick groundcovers like ivy and ice plant, and mulch. To make your garden less slug-friendly, you will need to either reduce and remove their hiding places, or use them as a trap (See below):
- Move soggy leaf or straw mulch away from your plants as soon as they come up in the Spring. Wait to mulch again until early summer when the soil and air is drier.
- Remove dead or damaged leaves from your plants year-round to encourage good air circulation and remove hiding places, especially around the root zone.
- In the fall, clean up garden debris and move it far from your garden beds to make it more difficult for slugs to lay eggs and overwinter.
- Put away your unused pots, planks of wood, and other garden clutter that could provide hiding places for slugs, snails and their eggs.
Water In the Morning
The best way to help prevent slug and snail damage is to keep plant and soil surfaces as dry as possible overnight. Always water very early in the morning rather than in the evening, so surfaces are dry by the end of the day.
Avoid overhead watering, as wet leaves are more vulnerable to damage from slugs and snails as well as from fungal disease. In areas with high rainfall or humidity, give plants extra space in the garden to promote good air circulation.
The best practice is to switch to drip irrigation on a timer. This does three really good things for your garden. Drip irrigation:
- saves water by irrigating directly at the root zone, through any mulch, saving you water and money. With a timer on your system, you can water at sunrise without even getting out of bed!
- eliminates overhead watering, which reduces wet foliage, preventing pests and disease
- greatly reduces the amount of time that the ground is moist, which makes your garden far less habitable for moisture-loving pests like snails and slugs.
Choose Slug Resistant Plants
Leaves with tender, delicate leaves and fruits tend to be slug magnets, including basil, beans, cabbage, dahlia, delphinium, hosta, lettuce, marigolds, strawberries, and small seedlings of all kinds.
Leaves that are thick, leathery, hairy or waxy resist their attacks, as do plants that are very aromatic. Where you can, choose plants that slugs don’t care for, like cyclamen, ferns, geraniums, lavender, nasturtiums, poppies, rhodededrons, rosemary, or sage.
Use Companion Planting
Some aromatic plants, such as rosemary, chamomile, chives, and garlic naturally repel slugs and snails. Planting these types of plants near or around other plants that are prone to slug and snail damage can help to deter them, if your problem is light.
Other plants are very attractive to snails and slugs, and can be planted next to the garden to distract and trap them. Good trap crops for slugs include chervil, marigold, and thyme. Combine trap crops with handpicking to effectively control moderate slug and snail populations.
One of the most basic and effective methods of controlling slugs and snails is by simply hand-picking them from your plants. This is best done at night when the pests are most active. Use a flashlight or blacklight around their hiding places and favorite places to feed and you will be able to spot them and their slime trails. (You can often collect caterpillars, hornworms and other pests more easily at night, too!)
Using gloves (to avoid the slime), pick off and drop any pests you find into a bucket of soapy water to kill them, or keep them in a closed container to feed to your chickens or opossums. Alternatively, you can harvest garden snails to eat yourself! Snails and slugs have a natural homing instinct, so if you don’t destroy them, you will have to take them very far from your yard, or they will just come back.
Handpicking for several nights in a row will greatly reduce pest populations. Once the population has noticeably declined, weekly hand-picking should be sufficient.
Cloches are small plastic or glass domes that go over individual plants to protect them from garden pests as well as from frost. They are great at guarding small seedlings against slugs and snails, as well as birds, squirrels and rabbits, because the pests cannot crawl up and over them.
Keep in mind that garden cloches are like mini greenhouses, and so they create extra heat and condensation around your plants. Make sure to lift them off or avoid using them on hot days, so you don’t overheat your plants.
You can purchase pre-made cloches, or make your own DIY cloches from repurposed plastic 2-liter bottles or milk jugs with the bottoms cut off and the caps removed.
Because snails and slugs like to hide in cool, dark, moist places during the day, you can trap these pests beneath board traps or flower pots that you position throughout your yard.
You can build board traps by raising 12- by 15-inch boards (or any easy-to-handle size piece of scrap wood) off the ground with 1-inch runners on two sides, like a very low table. The runners raise the board just high enough for slugs and snails to crawl underneath. Make sure both the board traps and the soil are nice and moist when you lay them down.
Lift boards daily and scrape off any snails and slugs you find. Destroy them away from your garden in a bucket of soapy water, feed them to your chickens, or harvest them for dinner. (see Handpicking).
Bread Dough Traps
Recent research from Oregon State University has found the most successful attractant for slugs is bread dough. Associate professor Rory McDonnell said, “They really, really like it. Bread dough outperformed everything.” In one instance, over 18,000 snails were trapped in 48 hours.
You can make bread dough using the researcher’s recipe and hand-pick the slugs from the dough, or turn it into a slurry to attract the slugs who then drown in the liquid.
Bread Dough Slug and Snail Trap
- 1 container with lid like a large, recycled yogurt container
- 1 cup flour
- 2 cups water, plus more as needed
- 1 packet baker's yeast
- Mix together the flour, water and packet of yeast. Knead into a dough for handpicking traps, or add more water as needed to make a slurry for drowning traps.
- Put your dough or slurry into ready-made slug and snail traps you can buy at garden supply stores, or make your own out of a mason jar or large, plastic yogurt container with a few snail-size holes cut into the lid.
- Bury the trap on the edge of your garden so that the opening of the trap is level with the top of the soil. That way, slugs and snails can fall easily into it.
- Check the container every morning and remove slugs. Keep your slurry or dough moist and refreshed for best results.
Slugs and snails are attracted to the yeast in beer as much as in bread dough, so placing several small bowls of cheap, yeasty beer as traps on the edges of your garden can be an effective way to control a small pest population.
Because both bread dough and beer are so attractive, you want to place your traps on the edges of your garden beds, so as to draw the slugs and snails away from your tender plants.
Your trap must be deep enough to drown them, and have vertical sides to keep them from crawling out. You will also need a lid of some kind to reduce evaporation and prevent rain dilution.
Be sure to bury the traps so that they are nearly level with the soil, and change the beer every few days to maintain its effectiveness.
You can buy ready-made slug and snail traps at garden supply stores, or you can make your own by burying a mason jar, small bowl, or large, plastic yogurt container so the rim is at ground level, and placing a lid with one or two snail-size holes cut into it over the container.
Diatomaceous Earth (DE)
Diatomaceous earth (DE) is a natural powder made from the fossilized remains of tiny aquatic organisms called diatoms that slugs and snails (and most hard-shelled insects) find difficult and dessicating to crawl through.
Barriers of dry diatomaceous earth heaped in a band 1 inch high and 3 inches wide around your plants have been shown to be effective at deterring slugs, as well as earwigs, mites, ants, fleas, pill bugs and other pests that have an exoskeleton.
However, diatomaceous earth loses all effectiveness as a pest control the moment it becomes wet, making it impractical as a slug barrier in most garden situations. However, it works great as a non-toxic pest control dust applied directly on infestations of aphids, ants, fleas, etc. both in the garden and around your home.
Encourage Natural Predators
Frogs, toads, snakes, birds, raccoons, opossums, turtles, ducks, and even chickens will eat slugs, snails and their eggs. Most terrestrial snail species make great escargot! Encourage natural predators by giving them habitat, like a small pond or water feature in your yard, or a small log and brush pile in a secluded or remote portion of your property.
You can also let your ducks or chickens loose in your garden or orchard to make quick work of slugs and snails there, if your plants are large enough to handle pecking and hopping around them.
Use Beneficial Nematodes
Nematodes are a class of tiny, beneficial worms that can be applied to the soil to control many types of pests. They tend to be voracious predators for their specific prey of choice, and make quick work of any that come in contact with them. Each species of nematode attacks different species of pests, so it is important to choose the right nematodes for the job you need them to do. The nematode varieties called Phasmarhabditis hermaphrodita and Phasmarhabditis californica, in particular, kill slugs and snails. They are the only varieties of nematode that are proven to do so.
Nematodes are applied to your soil by mixing them in water and applying them to your garden beds or planters according to directions on the package. Because they are living creatures, after you buy them, they will need to be stored in a dark container in the refrigerator, and used quickly.
Slug-killing nematodes can be purchased from gardening supply stores in Europe, but are not yet available in the U.S. (Although many other species of pest-control nematodes are available in the U.S.)
Chemical controls for snails and slugs can be effective when used in conjunction with an integrated pest management program that incorporates the other methods discussed above. Baits alone will not effectively control snails or slugs in the long term.
Slugs and snails experience an uncomfortable chemical reaction to their slime touching copper, so copper barriers can be an effective way to deter them—though they tend to work better in small applications like potted plants, rather than large garden beds. Here’s how to best use them:
- Make protective collars for your seedlings by wrapping them with a strip of 2-sided copper tape or flashing that is at least 3 inches wide so you can bury a portion of it 1 or 2 inches below the soil to prevent pests from crawling beneath the barrier.
- Nail or glue 2-inch wide copper foil or tape around the base of your pots and patio containers. Be sure to remove any pests present in the soil before applying the barrier, so you don’t undermine your efforts.
- Protect your trees by wrapping a 4-inch wide band of copper foil or mesh around the trunk, allowing for an 8-inch overlap around the trunk. Staple one end into the trunk, then connect the other end to itself with paper clips that will allow the copper band to slide outward and expand as the trunk grows.
To be effective against slugs and snails, copper barriers need to be at least 2 inches wide, and made with a high percentage of copper. Most copper tapes sold at garden centers are too narrow and too low in copper to be very effective, so look for thicker, wider copper tapes that are specifically made for shielding electric guitars and other electronics.
Copper barriers are effective until they become tarnished. When they do tarnish (which will vary based on your region and climate), you can clean them with a vinegar solution.
Iron Phosphate Bait
Iron phosphate bait pellets—available under many brand names, including Sluggo and Slug Magic—will cause snails and slugs to stop eating, however it can take several days to a week for the snails to die.
Iron phosphate is a natural mineral, and therefore it is acceptable for use in organic farming. However, iron-based slug pellets are not completely non-toxic to other animals. These pellets can kill earthworms and harm animals or people that ingest large quantities of them, so keep the package locked away from children, pets, and compost bins. But iron phosphate slug pellets are still a much safer alternative to metaldehyde slug baits.
Sprinkle snail bait pellets over the garden soil, near, but not on plants that are attractive to them, or near their favorite hiding places, such as under planters and irrigation boxes, close to walls and fences, or other moist, protected locations.
Apply the bait in the late afternoon or evening to take advantage of the nighttime feeding habits of these pests. Applying bait repeatedly in the same areas is best, because snails and slugs tend to return to food source sites.
Light watering after application helps these pellets to work better, because it encourages snails and slugs to forage. However, do not water heavily after bait placement, because you could bury the pellets in soil, wash them away, or make them moldy.
AVOID: Metaldehyde Bait
Slug and snail baits containing the active ingredient metaldehyde are easy to find in garden centers, and they are highly effective. However, metaldehyde baits are poisonous, particularly to dogs and cats, and the pelleted form can be very attractive to dogs. Some metaldehyde products are formulated with “carbaryl”, which is toxic to earthworms and soil-inhabiting beneficial insects.
Metaldehyde is not approved for organic farming. Do not use metaldehyde snail baits where children and pets could encounter them. Avoid getting metaldehyde bait on plants, especially fruits and vegetables.
AVOID: Salt or Ammonia
Both slugs and snails can be killed very effectively by either sprinkling them with salt or spraying them with an ammonia solution. But these chemicals also kill plants and soil life quite readily, and they can accumulate in your soil, so they are not recommended for slug and snail control in the yard and garden, or near storm drains, creeks, lakes, rivers or other waterways.
What Doesn’t Work to Control Snails – Common Myths
Contrary to popular garden folklore, crushed egg shells, coffee grounds, wood ash, pine needles, shredded bark mulch and wool pellets have all been tested and shown to be ineffective at deterring slugs and snails.
In fact, some experiments show that snails and slugs don’t seem to mind coffee grounds or egg shells one bit. And because calcium is an essential part of a snail’s diet (to maintain their shell), they may actually be attracted to egg shells!
Put your coffee grounds, wood ash, and egg shells to better use in your compost bin. Pine needles, shredded bark and wool pellets make outstanding mulches, but don’t count on them for slug control.