If you’ve ever noticed small, greenish marks that look like burns on plants in your garden, you may have fallen victim to hungry gastropods. Snail bites often appear overnight and can leave noticeable traces of slime behind.
While snails and slugs don’t actually have teeth to “bite” plants in the traditional sense, the damage they inflict has earned them this nickname.
If you’re short on time, here’s a quick answer to your question: Snail bites are the holes and markings left behind on plants when snails or slugs feed on them, usually overnight. The snails scrape away at leaves, stems, flowers, and fruits with their radulas, which function like raspy tongues, leaving behind telltale slime trails.
In this comprehensive guide, we’ll cover everything you need to know about snail bites, including what they look like, what causes them, which plants are most vulnerable, and how to prevent slugs and snails from damaging your garden.
What Do Snail and Slug Bites Look Like?
Small irregular holes in leaves/petals
One of the most common signs of snail or slug damage is small, irregularly shaped holes in leaves, flowers, or other plant parts. These holes are caused by the rasping mouthparts of snails and slugs as they feed on the plant material.
The holes may range in size from pinholes to larger gaps, depending on the size of the snail or slug doing the feeding. Often the holes will have uneven, jagged edges as the mollusks chew through the greenery.
Snails and slugs typically feed at night or on cloudy, humid days. So you may notice new holes in your plants overnight or after a rain. The holes are often concentrated along the edges of leaves or petals as the pests eat from the perimeter inward.
With heavy feeding, leaves can appear skeletal or lace-like due to the amount of missing material. Flowers can also be riddled with holes, marring their appearance.
Some signs that snail or slug damage may be the culprit include:
- Irregular hole sizes and shapes
- Jagged, torn edges around holes
- Holes concentrated near edges and along veins of leaves and petals
- New holes appearing overnight or after rain or watering
Distinguishing snail vs slug damage can be tricky since their feeding patterns are so similar. However, slugs often leave behind telltale slime trails on plants that shine silver when dry. So if you see the shiny slime, slugs are likely the offenders!
Burn-like lesions on stems, leaves, flowers
In addition to leaf and flower holes, snails and slugs can leave other characteristic damage on plants. One common type of injury is lesions or wounds on stems, leaves, or other parts that appear burned, scorched or sunken.
These lesions are caused by snails and slugs feeding on and destroying the outer plant tissues. As they rasp away material with their radulas, lesions form at the feeding sites. The damaged areas often look brown, blackened or shriveled, similar to a burn or blight.
Some common signs of snail/slug lesions include:
- Sunken, browned areas on leaves, petals, stems
- Blackened, withered patches on flowers
- Lesions concentrated along leaf veins or edges
- Scarring and wounds on soft plant tissues
- Silver slime trails nearby
Slug slime contains enzymes that help break down plant matter as they feed. This can worsen the lesions and increase decay or wilting of the affected parts. Prompt removal of snails and slugs at first sight of lesions can help reduce further damage.
Wilting/loss of rigidity in affected plant parts
As snails and slugs feed on plants, one sign of their damage is wilting, drooping, and loss of rigidity in the affected parts. This wilting is caused by the snails/slugs destroying the plant tissues as they feed and interrupting the flow of water and nutrients within the plant.
Leaves or stems that appear limp, flaccid, or rubbery may be under attack by these slimy pests. Wilting often starts along the edges of leaves or on individual branches/stems where feeding is concentrated. But it can spread to the entire plant if infestation is high.
In addition to wilting, other signs of snail/slug activity leading to loss of rigidity include:
- Drooping or downward curling of leaves and flowers
- Stems and petioles collapsing or bending easily
- Young shoots becoming limp or rubbery
- Supported plants (like tomatoes) leaning over
- Slimy silver trails on affected parts
Severe snail and slug feeding can interrupt water flow enough to cause wilt even before major holes or lesions occur. Pay attention to any drooping plants and look for slime trails. Removing pests promptly can minimize damage and let the plant regain its strength.
What Causes Snail and Slug Biting Damage?
Both snails and slugs can cause annoying and even serious damage to plants with their raspy teeth-like structures called radulas. The slimy creatures use these tooth-like structures to scrape and chew holes in plant tissues as they feed.
While the holes may seem small, the chewing damage can add up over time, especially when large numbers of snails and slugs feed on plants.
Chewing damage from raspy radulas
A snail or slug’s radula looks like a ribbon covered in rows of tiny sharp teeth—almost like a microscopic cheese grater. As these slimy mollusks feed, they use their radulas to scrape up pieces of leaves, fruits, stems, tree bark, and other plant tissues they find tasty.
The physical damage from all that rasping and grinding alone can be enough to stunt plant growth or even kill off delicate seedlings.
Saliva injected during feeding causes further tissue damage
Making matters worse, snails and slugs also inject saliva into the plant tissues they chew on. Researchers have found enzymes and harmful chemicals like calcium oxalate crystals in snail and slug saliva that break down cell walls and cause plant tissues to decompose faster.
This saliva takes the physical chewing damage to another level, causing more extensive die back around the feeding sites.
Slime trails often left behind
The slime trails that snails and slugs leave behind as they travel across plant leaves, stems, and bark also facilitate damage. Their mucus helps the rasping mouthparts glide more easily across plant surfaces, allowing snails/slugs to feed more efficiently.
The slime contains chemicals and microbes that can inhibit plant growth and damage surface tissues too. Plus, the mucus trails essentially paint targets on plants, luring additional snails and slugs to feed there as well.
With their chewing mouthparts, cell-damaging saliva, and slime trails, both snails and slugs can seriously impact gardens and crop fields. Getting rid of them or blocking access to plants is key to prevent ongoing feeding damage from these slimy plant pests.
Which Garden Plants are Most Vulnerable to Snail Bites?
Leafy greens like lettuce, spinach and kale
Leafy greens such as lettuce, spinach, and kale are among the most vulnerable to damage from snail bites. Their tender, lush leaves make an irresistible snack for these slimy mollusks. Snails use their raspy tongues, called radulas, to scrape away at the vegetable leaves, leaving unsightly holes and shredded edges on the plants.
Lettuce is especially at risk, as snails favor these tender leaves above almost any other garden offering. The edges of lettuce leaves left overnight often appear scalloped the next day, as snails have nibbled their way along the perimeter.
Spinach and kale leaves may be dotted with small holes where snails have fed.
Snail damage on leafy greens can quickly add up to complete destruction of young seedlings. Even larger, established plants can be decimated within just a couple nights of heavy snail traffic. To prevent snail bites, gardeners use remedies like copper tape as barriers, traps made from beer-filled jars or boards, or iron phosphate bait scattered around vulnerable plants.
Brassicas including cabbage, cauliflower and broccoli
Much like leafy greens, brassicas including cabbages, cauliflower, and broccoli also tend to show extensive damage when snails move in. Their broad tender leaves seem to invite snails to stay awhile and dine. Seedlings are very vulnerable and are easily chewed to the ground.
Established plants show raggedy-edged leaves and stalks gnawed by hungry snails. Heads of cabbage or cauliflower may have chunky holes chewed into them. Broccoli heads often have numerous deep pockmarks where snails have excavated the tiny tender buds.
| Brassica | % of gardens affected by snail damage* |
|---|---|
| Broccoli | 35% |
| Cabbage | 67% |
| Cauliflower | 44% |
To protect brassicas, gardeners often resort to row covers over plants, copper tape barriers around beds, handpicking snails after dark, and scattering snail bait. Keeping mulch well away from the base of plants also limits shelter for the pests.
Herbs and seedlings
Delicate herbs like basil, parsley, cilantro, and dill make perfect snail fodder. Their small size makes them very vulnerable, and snails can quickly devour seedlings and damage harvestable leaves and stems.
Snails especially favor basil, leaving wispy shredded leaves and stems in their wake. Parsley and cilantro grow so fast that some nibble damage may be tolerable. Keeping seedlings under cloches until better established is advised.
Almost any seedling, herb or vegetable, is at risk while in the cotyledon stage with those first tender sprouts. Snails can wipe out a whole tray of seedlings overnight if given the opportunity. Careful use of predatory nematodes, diatomaceous earth sprinkled around plants, and beer traps can help reduce damage.
If garden snail damage occurs regularly, seek out their daytime hiding spots under boards, in tall grass and under debris and dispose of them. Limit nearby compost piles which can breed more snails. Keep the garden free of leaf litter and maintain beds clear of weedy growth.
How to Prevent Snails from Damaging Plants
Remove hides like boards and dense groundcovers
Snails thrive in moist, shady areas and will congregate under boards, dense groundcovers, piles of leaves, garden debris, and other hides. Regularly removing these hides eliminates cool, damp places for snails to congregate during the day when they are not active.
This forces them into the open where they are more vulnerable to natural predators and control methods.
Use barriers like copper tape and abrasive diatomaceous earth
Snails and slugs avoid crossing copper because it causes an electrical shock that repels them. Copper tape wrapped around planting beds, pots, or tree trunks creates an impassable barrier that keeps snails out of planting beds.
Likewise, abrasive diatomaceous earth sprinkled around plants causes snails to dehydrate and die when they crawl across it.
Hand pick active snails
Actively hunting for snails is one of the most effective ways to eliminate them. Get a flashlight and gloves and head out at night when they are most active. Collect any snails you see and drop them into a bucket of soapy water to dispatch them.
Their hiding spots under boards and groundcovers are also ideal places to hunt for them.
Set out beer traps
Fill shallow containers with cheap beer and place them around the garden. The smell of the fermenting beer attracts snails who will crawl in and drown. To increase effectiveness, dig the containers into the ground so the rim is at soil level. Check traps daily and replenish the beer as needed.
Encourage natural predators like birds and ground beetles
Instead of always resorting to chemical or physical control, allow natural predators to thrive in your garden. Ground beetles, frogs, toads, turtles, and birds all feed on snails and can significantly reduce populations when present in your garden.
Avoid pesticides that might eliminate these allies and include plants that provide food and shelter for these animals.
What to Do if You Already Have Snail Damage
Apply slug bait or iron phosphate sprinkles
If you already see damage from snails and slugs, it’s time to take action. Applying slug baits or iron phosphate sprinkles can quickly kill the culprits and prevent further destruction. Look for products like Sluggo or Escar-Go which use iron phosphate, a natural molluscicide.
Lightly sprinkle the pellets around affected plants, concentrating extra near the stems or trunks. The snails and slugs are attracted to the bait, eat it, and then expire within 3-6 days. Unlike old-school metaldehyde baits, iron phosphate products are safe for kids, pets, and wildlife when used as directed.
Spray plants with molluscicide
For quicker control, you can spray liquid molluscicides directly onto plants. Look for products with the active ingredient metaldehyde or iron phosphate. Completely coat the leaves, stems, buds and surrounding soil area. The molluscs will die upon contact. Reapply after rain or every 5-7 days.
Take care not to spray during the heat of the day which could possibly burn delicate plant tissues. And always keep these chemicals away from areas where children or pets could come into contact.
Cover vulnerable plants overnight
As an organic approach, you can protect plants by covering them at night when snails and slugs are most active. Old flower pots, plastic nursery pots or homemade tents of landscape fabric work well. Be sure to weigh down the edges so the pests can’t squeeze underneath.
Remove the covers in the morning after the sun has warmed things up and sent the molluscs into hiding. This method takes some time each evening, but can protect precious ornamentals or edibles without chemicals. For smaller potted plants, bring them indoors at night.
Conclusion
Snail and slug bites may look like chemical burns, but the damage is actually caused by the rasping radulas of these slimy garden pests as they feed. All tender vegetation is at risk of overnight grazing.
While snail bites can’t be reversed, taking proactive measures like removing hiding spots, applying barriers, hand picking active snails, and encouraging natural predators can help protect plants.
By understanding what snail bites look like, what causes them, which plants are most vulnerable, and how to discourage these pesky molluscs, you can defend your garden from further damage. Stay vigilant for the telltale slime trails and leaf lesions so you can take action before slugs and snails have a chance to feast.
