- Grow Your Own Magazine
- Snail Damage In Your Garden
- Slugs and Snails
- Snail Damage
- Cultural Practices to Discourage Snails
- Natural Snail Repellents
- Snail Bait
- Beer Traps
- Slugs and snails: how to recognise damage?
- How to Naturally Keep Snails + Slugs Out of Your Garden (Without Commercial Products)
- What do Land Snails Eat?
- Snail diet
- A singular mouth
- A problematic diet?
- Snails as pests
Grow Your Own Magazine
Yes there are issues be careful to wash any slime trails off of lettuce as well as the slugs.
“The normal life cycle of the lungworm A. cantonensis involves rats (definitive host) and snails or slugs (intermediate hosts), and also transport hosts such as crabs, freshwater shrimps, fish, reptiles and amphibians who feed on them.
Humans are incidental hosts and acquire the infection by eating raw or undercooked infected snails, slugs, crabs or freshwater shrimps, or by eating raw vegetables contaminated by a small snail or slug.”
Adult worms of A. cantonensis live in the pulmonary arteries of rats. The females lay eggs that hatch in the terminal branches of the pulmonary arteries.
Larvae migrate to the pharynx, and are then swallowed and passed in the faeces. The larvae penetrate or are ingested by an intermediate host (snail or slug). Third-stage larvae are produced, which are infective to mammals.
When the mollusc is ingested by the definitive host, the third-stage larvae migrate to the brain where they develop into young adults. The young adults return to the venous system and then the pulmonary arteries where they become sexually mature.
In humans, juvenile worms migrate to the brain (or, rarely, the lungs), where the worms ultimately die.
The life cycle is similar except that the adult worms live in the arterioles of the ileocaecal area of the definitive host.
In humans, A. costaricensis often reaches sexual maturity and releases eggs into the intestinal tissues. The eggs and larvae degenerate causing severe local inflammation and do not appear to be shed in the stool.
Symptoms are caused by the presence of larvae and local host reactions in the brain.
Symptoms include severe headaches, nausea, vomiting, neck stiffness, seizures, and paraesthesiae.
This presents with acute abdominal pain in the right lower quadrant, associated with prolonged fever, anorexia and eosinophilia. Infection usually involves the terminal ileum, appendix or ascending colon.
Angiostrongyliasis. Angiostrongylus Infection information. Patient | Patient
Snail Damage In Your Garden
A garden is hard work. You do everything right and follow all the instructions for how to plant it and maintain it. Everything is coming together and you are starting to see new growth. Seedlings and coming up, new leaves and flowers are appearing, it seems like you are well on your way to your first real fruit and vegetable production. Then you see it. You wake up one morning and there are ragged leaves full of holes that appear to be completely shredded. Your garden is the newest victim of snail damage.
Luckily this damage is only temporary, if you address it quickly. It will take time for damaged plant material to disappear and new growth to replace it. But like all pests, once the snails are eliminated there are multiple preventative methods available to stop them from returning to your garden in the future.
Slugs and Snails
Slugs and snails are quite different from other common garden pests as you can see by their slimy appearance. They are mollusks and leave slimy trails in their wake as they slide across plant leaves. This slime is actually called mucus (gross, right?) Slugs and snails produce mucus to allow themselves to move on the ground. This mucus helps them retain moisture when crossing dry surfaces and protects them from being cut by sharp objects they may cross.
Both slugs and snails are part of the same class called gastropods. Most gastropods live in water, with snails and slugs being the only ones that are also found on land. The main difference between them is that snails have shells while slugs do not. Since slugs have no shells, they are able to hide themselves better than snails by fitting underneath logs, stones or other debris on the ground. As a result, you’re probably more familiar with seeing snails since their shells are so obvious to see.
Snails seek out new, tender plant growth, making your developing garden a prime target for their feeding activity. While the damage they cause to tender growth is obvious, few people are aware that snails also eat plant roots, stems and fruits.
Since snails are nocturnal and feed at night, you may not notice their presence in your garden until you actually see snail damage on plants. Snail damage is most obvious when large, ragged holes are seen on leaves. They are especially active at feeding early in the spring when new growth is most vulnerable to their feeding. You also may see their mucus trails in your garden (hopefully before any major damage occurs.)
Cultural Practices to Discourage Snails
Before jumping into the use of repellents and pesticides, start by making adjustments to cultural practices in your garden to make it less inhabitable for slugs, snails and other pests. The use of integrated pest management is the foundation of our lawn and ornamental pest control services because remedying the source of pest problems is highly effective.
Materials such as gravel, woodchips and sand are difficult for snails to climb over, making these materials excellent protective barriers in and around your garden. Proper placement of plants in your garden and frequent trimming will eliminate many favorite hiding places for slugs and snails since during the day they prefer dark and moist locations. Remove any debris from your property such as leaves or rotting wood on the ground.
Physical removal of snails is an often overlooked method that is as natural as you can get. By hand picking snails from your plants in the early morning or evening when they are most active and you can still see them, you will immediately eliminate the direct source of snail damage. While you may not be able to remove them all, it certainly will put a dent in their population.
Many pests are attracted to landscapes with excessive moisture. By cutting back irrigation and allowing your garden to dry out more often, the plants will be less stressed and the environment will be less attractive to snails.
Another more costly method of reducing the moisture caused by irrigation would be switching to a drip irrigation system. Drip lines will limit the volume of water applied at one time and also eliminate the use of overhead irrigation which is a common cause of fungus on plants.
Natural Snail Repellents
In the battle against snails, there are many tools at your disposal. If you are expecting to eat the fruits and vegetables produced in your garden, chances are you will prefer to use natural snail repellents to avoid the use of more traditional pesticides (although we’ll talk about safe snail baits soon.) While natural products don’t last as long, they can get the job done if used properly and frequently.
Diatomaceous Earth is known by many as a great non-toxic, food grade pest control product that will certainty kill snails and slugs. Diatomaceous Earth is made from the fossilized remains of tiny acquatic organisms. Can’t get more natural than that! This product causes insects, including snails, to dry out and die. The problem is it needs to be kept dry to be effective so it doesn’t last long at all outside.
Coffee is another natural snail repellent although it is also quite temporary in natural. Coffee grounds can either be sprinkled on the ground around plants or sprayed on plants, soil and snails. If coffee doesn’t prove to be effective, at least you’ll have plenty left over to keep you awake in your snail fighting journey!
Egg shells. Yes, there is finally a use for them. Many gardeners use egg shells as a physical barrier around their landscape to deter snails and slugs. The sharp edges of egg shells will be very uncomfortable if these pests try to cross over them.
Copper is another natural snail repellent that is so effective it is actually sold in many plant nurseries. Applied as a tape around the perimeter of your garden, it will repel snails and slugs by reacting with their mucous and actually shocking the snails.
Plants that repel snails. Certain flowers and herbs are great at repelling snails. These include flowers such as hibiscus, azaleas, daylilies, and foxglove and herbs such as rosemary, mint, parsely, fennel and basil.
Molluscides. Yes, that’s a real word. Pesticides that are used against mollusks, which includes snails and slugs. Favorite baits in use by professional pest control services include the active ingredient metaldehyde.
While effective, metaldehyde is also toxic and should be used as a last resort against snails. A safer bait that we prefer to use in our clients’ gardens in West Palm Beach is Intice 10 (Boric Acid.) This boric acid based bait is also extremely effective when used in home pest control services.
Another popular bait is iron phosphate, often sold in garden centers and hardware stores. This bait causes snails to stop feeding, resulting in them starving to death. This product is approved for us in vegetable gardens and is non-toxic.
While technically not a bait, beer traps are certainly a fun tool to incorporate into your anti-snail arsenal. Get inside the mind of your enemy and put these traps in hiding spots that snails would love to find. Any container like a bucket or tuna can may be filled mostly with beer and placed in your garden. Snails are attracted to the smell of beer and will drown when the fall into your trap.
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Slugs and snails: how to recognise damage?
How to prevent (further) damage?
There are a lot of things you can do to get rid of slugs and snails. Make sure to carefully organise your garden and to keep it tidy. This ensures that slugs and snails have less shelter. Also work the ground regularly to kill slugs, snails and their eggs. Additionally, don’t rid your garden of natural predators like hedgehogs and toads. Slugs and snails don’t like strong smells, like coffee grounds or garlic. Another thing they hate is copper.
More specifically, you can surround your plants with a sharp surface. Egg shells, gravel or sea shells are hard to cross for slugs and snails. You can also place a slug fence. This barrier out of plastic or netting can be placed around your plants. The top edge is turned back at an angle of 30 degrees. Slugs and snails cannot cross it because of this. Finally, you can place small containers with beer in the soil. Slugs and snails love the yeast in beer and will drown in it.
About slugs and snails
Slugs and snails come in all colours and sizes. Snails have a shell, whereas slugs do not. They have a tongue that contains thousands of miniscule teeth. This tongue works like a file, ripping leaves into small pieces. The top speed of most common garden snails and slugs is about 45 metres per hour. They enjoy cool and humid environments.
How to Naturally Keep Snails + Slugs Out of Your Garden (Without Commercial Products)
Some gardeners are so frustrated with snails and slugs dining on their plants that they head to their local garden center to grab the first snail-killing product they can find. Before you move to more expensive or lethal methods that could also harm desirable insects and animals and may be overkill, try these natural, non-toxic and (mostly) non-lethal home remedies for snails and slugs to protect your garden.
13 Non-Toxic Methods to Protect Your Garden from Snails + Slugs
1. Remove them by hand.
Removing snails from your garden by hand requires no products or special tricks; however, it does take time, may not be a permanent solution and requires that you are okay with touching snails. If you have the time and patience to use this method, you will need to regularly check your garden for snails and, when you find one or more, you will need to pick them off of your plants and move them at least 20 feet away from plants that you do not want them to eat.
2. Add a layer of gravel, bark or wood chips to your garden beds.
It is more difficult for snails to get around when they are trying to slide their way over gravel, sharp sand or wood chips, so adding this type of material around your plants can help reduce the chances of them being eaten by slugs or snails.
3. Water your garden in the morning.
It is also more difficult for snails to get around on dry soil than moist soil. Since snails like to do most of their garden-destroying at night, water your plants in the morning. By using this earlier irrigation method to control snails and slugs, you will give the top layer of soil more time to dry out before night falls and the snails start making their way to your backyard buffet.
4. Add copper.
When snails touch copper, their slime reacts in a way that they receive an uncomfortable electrical shock that will quickly encourage them to turn around and find somewhere else to dine. Adhesive copper tape is available at home improvement stores, garden centers or online and is the most convenient way to ward off slugs and snails with copper. If you go the adhesive copper tape route, you can simply run the tape along the edges of your garden beds to keep snails from entering.
If you do not want to purchase copper tape or just happen to have a jar of copper pennies lying around, you can also use pennies to protect your garden. When using pennies, you can glue them to your garden bed to keep them in place and will want to make sure they are very close together so you do not leave pathways for smaller snails and slugs to sneak through.
5. Attract birds to your garden.
Many types of birds eat snails and slugs. When invited into your garden, they will be more than happy to help you in removing the snails that have found their way into your garden. While this is lethal for the snails, you are encouraging nature to take its course – rather than introducing chemicals into your garden or sending the snails and slugs to a slower death with drowning or poison.
6. Rescue chickens.
Chickens are great for your garden for a variety of reasons and, fortunately for gardeners who hate this particular garden pest, eating snails and slugs (and their eggs) is one of them. Chickens help control a variety of unwanted insects and other pests, including these little land mollusks, while also helping to turn the soil, providing manure for composting, and laying eggs.
7. Sprinkle broken eggshells.
Broken eggshells have sharp edges that will hurt snails and slugs if they try to crawl over them. Therefore, if you did end up rescuing some chickens and are using their eggs or have some store-bought eggshells left over from breakfast, you can break them up into small pieces and sprinkle them around your plants or around the edge of your garden beds. The eggshells will eventually break down and add nutrients to your soil, so that is an added benefit.
8. Sprinkle coffee grounds.
Another way to deter slugs and snails from entering your garden is to sprinkle coffee grounds around your plants or the borders of your garden. Like eggshells, coffee grounds will also add nutrients to your soil.
9. Spray plants with homemade snail repellent.
You can make a homemade snail repellent by mixing garlic and water in a spray bottle or pouring cold coffee into a spray bottle. You can then take that spray bottle out to your garden and spray your plants and the area around your plants to deter slugs and snails. If you are trying to naturally deter your slugs and snails without killing them, be sure that you do not spray them directly with the coffee.
10. Plant sacrificial plants.
Sacrificial plants, also known as trap plants, help protect your garden from pests by attracting the pests elsewhere. For example, if you are trying to protect an ornamental garden bed from snails, you can plant some lettuce in the back or in less-conspicuous spots. Snails like the taste of lettuces better than most ornamental plants, so they will more likely dine on your lettuce leaves than your pretty plants.
11. Deter them with herbs.
Lavender, sage, rosemary, parsley, creeping thyme and mint are all nice additions to an herb garden that also happen to deter snails. If you were planning on planting some of these anyways, plant them around the border of your garden or between vulnerable plants to help ward off these midnight marauders.
12. Set up citrus traps.
Save your lemon, lime, orange and grapefruit peels to scatter around upside down in your garden before nightfall. In the morning, you will likely find a good portion of your slug and snail population has found its way to these tasty treats. Collect them and move the snails and slugs somewhere far from your garden or, if you prefer, set them out in the open where birds and other predators will eat them.
13. Plant marigolds away from your garden.
Marigolds are a mainstay in the world of natural pest control methods; however, we are usually planting them near our gardens to ward off a variety of pests. Snails are actually attracted to marigolds, so if snails are the problem you are trying to fix, you will need to plant your marigolds away from your garden, rather than near it.
What are your favorite natural, non-toxic methods for keeping snails and slugs out of your garden?
What do Land Snails Eat?
Snails feed on a variety of food found in their natural habitat. What they consume depends on where they live and the species of snail that they are. Some conventional foods are plants, fruits, vegetables, and algae. Plants that are dying are often a good meal for them, and they also eat sand or soil when seeking for calcium to get a thicker shell.
Most terrestrial snails are herbivorous, but others are omnivorous and some even carnivorous. Each species has different eating habits, depending on their size, age, habitat and individual nutritional requirements. You will likely find snails around your garden as this offers them plenty of fresh plants and leaves to eat.
The herbivorous snails devour a wide variety of live plant parts: leaves, stems, plant crops, bark, and fruits. Many consume fungi and mushrooms, and others may occasionally add algae, although these are an important food for freshwater snails.
Some snail species enjoy plants that are already dead, as well as animals or any dead organic matter. These individuals are detritivores because they feed on debris or solid residues that remain in the soil.
Carnivorous snails eat several types of small animals; this is the case of the species of the genus Powelliphanta, which live in New Zealand and feed on other gastropod mollusks such as slugs and earthworms, among other terrestrial animals.
On the other hand, omnivores can include plants and animals into their diet, but usually, these animals prefer other terrestrial animals, so they are practically predators. For example, the species Rumina decollata can eat other species of conch, slugs, annelids like worms and, to a lesser extent, plants.
Snails have to feed on foods that include significant amounts of calcium to keep their shell hard. When looking for food they use their powerful sense of smell.
They are nocturnal so that they look for food during the night or the very early morning hours. (2) They consume more food than usual if the winter approaches so they can store up fat reserves to live on while they hibernate.
When food sources are very low in the summer or spring months, they may voluntarily put their body into a state of estivation as well. This process allows them to survive in severe conditions of drought. (3)
A singular mouth
The mouth of terrestrial snails is unknown to most people. Have you ever wondered how they eat? These mollusks have an organ in the mouth with rows of tiny teeth, sometimes compared with a tongue, fully functional at the time of eating.
The radula is this structure inside the snail’s mouth that has rows of chitin teeth. When the food reaches this structure that looks like a sac, the teeth do not cut or grind it like human teeth would. Instead of being chewed, the radula scrapes the food and breaks it, before it passes through the esophagus to continue the digestion process.
These tiny teeth suffer much wear and tear as time passes. Therefore, they are continually replaced by others. Not all species have the same number of teeth. Some have rows with a few, but in others the number reaches hundreds.
Snails are often said to be very noisy eaters. However, the sounds you hear aren’t them consuming the food. It is the radula tearing and scraping the food.
A problematic diet?
A Massive number of snails in a garden or even worse in farms with crops can quickly become a serious problem. They will consume enough to ruin the harvest.
Certain terrestrial species, such as the Giant African Snail (Achatina fulica), are a headache for farmers and owners of crops since they have no scruples about consuming economically valuable plant species such as cacao, cucumber, papaya, Bean, squash, cauliflower and some cereals, just to name a few. This species, considered in many countries an invasive animal, generates important economic losses.
Snails as pests
You may have never seen a terrestrial snail eat, but its appetite is huge. In fact, in many places, these eating habits mean a real problem for humans.
If you use herbicides or pesticides on your plants, you may be causing the death of many snails without even realizing it.
Some with gardens or farms strive to trap the snails rather than killing them. They either release them back into a new environment, or they sell them. One of the easiest ways to catch them is to place lids of jars with some beer in the garden.
Large farms with large land extensions have another way to deter snails from eating their crops. They put 6-inch screens of copper on the ground. The slime from the snails doesn’t seem to mix very well with the copper, and that means they will stay away from the crops. This method has been very successful.
In spite of the above, other snails have been used in turn as pest controllers, since they eat harmful parasites to some plants.
BioExpedition Publishing © 2017.
How to Get Rid of Slugs
- You can create the perfect slug trap by laying boards or pieces of cardboard on the bare soil around your plantings. Each morning, turn the boards over and scrape the hiding garden slugs into large plastic containers. Cover and place in freezer for three hours. When frozen stiff, dump them on your compost pile.
- Place shallow dishes of beer around the garden to lure the slugs to a drunken death. Or mix water with molasses, cornmeal, flour, and baking yeast to replace the beer. These are both great slug baits that can help control your garden slug population.
- Some slugs are a bit beer-resistant and might crawl out of the dish. If you find this happening, try creating a beer trap that they can’t escape from: Cut the spout end off a plastic beverage bottle just where it reaches the fattest diameter. Now, turn the pour-spout around so that it’s pointing inside the bottle and fasten it with staples or duct tape. Pour a little beer into the bottle (add extra yeast, if desired) and lay it on its side in the garden.
- If necessary, get out and handpick the little rascals—a task best undertaken in the evening twilight or in the early light of dawn, before they have sought shelter from the heat of the day.
- If you need a slug repellent to keep slugs away from tender plants, circle them with wood ashes (which are also a good source of potassium for your plants), diatomaceous earth, copper sheeting, coffee grounds, pine needles, coarse snad, or crushed eggshells. These rough mulches rip up a slug’s tender underside.
Photo Credits: GrowVeg.com. Prevent slug damage like this with the above tips for getting rid of slugs.
- Alcohol kills these pests by acting as a surfactant, or wetting agent, that can penetrate an insect’s waxy coat of armor and kill on contact with the body. Isopropanol (rubbing alcohol) works fine and is easy to find, but be sure it doesn’t have additives. Ethanol (grain alcohol) seems to work best. Alcohol usually comes in 70 percent strength in stores (or 95 percent strength purchased commercially). To make an insecticidal spray, mix equal parts 70 percent alcohol and water (or, if using 95 percent alcohol, mix 1 part alcohol to 1 ½ parts water).
- A spray of cold coffee can control small slugs, but it must completely drench them to be effective.
- Some plants have been shown to do well despite being around slugs. If you tend to have slugs and are having trouble getting rid of them, try planting astilbe, phlox, or mint to reduce damage.
- Check out this video about controlling slugs and snails in the garden and this blog with more tips on how to naturally get rid of slugs.
- Try this old-fashioned advice from The 1963 Old Farmer’s Almanac: A mulch of oak leaves is useful against slugs. To control slugs, our grandparents strewed leaves of lettuce, spinach, cabbage, or slices of raw potato in the garden. The night feeders collected beneath these materials, and the next morning they were gathered and eliminated. Frogs and toads are good consumers of slugs. Old timers, living by their wits, learned to make use of simple materials for insect control. They found that slugs do not like alkaline ground. Slaked lime, wood ashes, slag, sand, and cinders were useful against slugs.
How to Prevent Slugs
- It is helpful to rake your garden in early spring in order to clean up some of the moist debris that slugs love, as well as to rake away any slug eggs. Large wood chips also provide hiding areas for slugs, so try not to use them.
Photo Credit: GrowVeg.com. Prevent slugs in your garden by getting rid of slug eggs.
- Only water your garden when necessary so as to minimize the damp places in which slugs congregate.
- Slugs have many natural predators. If you have chickens or ducks, they will help by eating slugs and their eggs. Also, be sure to encourage the populations of snakes, turtles, frogs, toads,and ground beetles in your garden. Firefly larvae are also natural predators, so find out how to attract fireflies to your garden. The same goes for songbirds, so check out our tips on creating a bird-friendly habitat.
- Slugs experience a small shock when exposed to copper, which will make them turn back. Try making a perimeter around your plants with copper tape.
- Companion planting is a great way to prevent pests. In order to keep slugs away from more valuable plants, place plants that slugs love near your valuables as a trap, and then destroy the infested plants. Good traps for slugs include chervil, marigold, and thyme.
Field Slug – By Michal Horsák , via Wikimedia CommonsEverything about slugs and snails in your garden isn’t bad.
In the garden folklore, slugs and snails are weather detectors. “When the black snail does cross your path, black cloud much moisture hath.” Snails climbing trees are a harbinger of hot weather. Slugs burrowing deep into the ground in summer are a sign of impending drought, and slugs burrowing deep into the ground in autumn are a sign winter is coming soon.
There’s no doubt that slugs and snails help to clean up garden debris. Almost all common garden snails and slugs (except the uniquely destructive Field Slug Deroceras reticulatum), prefer dead garden detritus to living plants. Their feces make a nitrogen-rich, mineral-laden fertilizer that enhances plant nutrition.
Of course, there are many ways snails and slugs are bad for your lawn and garden. Snails don’t do a lot of damage at ground level, but they are strong climbers. They find their way up flowering plants to eat flower buds. They climb fruit trees and feast on fruit just as it is turning ripe. They strip bark off young trees and chew smooth, irregular holes through leaves. Or they just live underground and eat the roots like the Keel Slug.
Slugs can be even more destructive. They may devour bulbs while they are still in the ground. They mow down seedlings as soon as they emerge from the ground. They leave a slimy trail everywhere they go that attracts other slugs.
While snail and slug damage to garden plants is bad, some things about slugs and snails in your garden are very bad. There is one very good reason every gardener needs to minimize contact with slugs and snails: They spread disease.
Both garden snails and garden slugs are potential hosts of the rat lungworm, Angiostongylus cantonensis. This parasitic nematode primarily infects rats, with adult worms infesting the blood vessels that transport blood from the lungs to the heart. Eggs hatch inside the rat, crawl out of the lungs and into its mouth, and are eventually discharged in feces. Snails eat the feces and a new batch of lungworms hatches inside them.
If other rats eat the infected snails, the cycle continues, but if humans eat the infected snails, the parasite takes a different path. In humans, rat lungworms travel to the brain. The worms initially lodge themselves in the meninges covering the brain. They may burrow into the brain itself, causing high pressure in the fluid of the brain and spinal column and damaging brain tissue. The immune system fights the infection with high fever. How much damage is done to the brain depends on how many worms are consumed with raw snails, their feces, or their mucus. It is not necessary to eat “snail sushi” to get the infection. You can also get it from unwashed vegetables that are contaminated by slime from infected snails. This infection was first reported in the southern United States in 1987, and occasionally occurs in Britain.
A closely related parasite called Angiostrongylus costaricensis is also spread by rats and snails to humans. It infects the intestines rather than the brain. Once it is inside a human host, it never leaves. It is not expelled with human feces. This parasite can cause severe intestinal problems. Most of the cases of this infection in human hosts have been recorded in Central and South America. In both Britain and the United States, yet another parasite in the same genus, Angiostrongylus vasorum, causes lungworm infections in dogs, and a similar species called Aerlurostrongylus abstrusus infests the lungs cats. Neither dogs nor cats commonly eat snails, but puppies and kittens experiment and can get infected. Cats and dogs can also become infected if they eat other animals that have eaten infected slugs or snails.
A liver fluke called Dicrocoelium can be transmitted from snails to cattle, sheep, and people. These tiny liver worms make a temporary home in snails until they are expelled in slime balls. Ants eat the slime, and people (as well as grazing animals) get the flukes when they accidentally (or intentionally) eat uncooked ants.
Several thousand people every year contract parasites from contact with garden slugs and snails. Uncounted hundreds of millions of plants, of course, are devoured by these slimy invaders to the garden.
Snails and slugs alike can transmit Salmonella, which causes severe food poisoning.
If you would like to learn more about which are the best methods for trapping and killing these slimy animals the read these two articles The Top Three Slug and Snail Traps and Poisons and the Top Three Snail and Slug Repellents and Barriers.