Snails are familiar slimy pests that cause havoc in the garden, eating and making holes in leaves, stems and flowers.
What are snails?
Snails are soft-bodied molluscs, with a hard shell, that eat holes in leaves, stems and flowers of many plants.
The snail most commonly encountered in gardens is the common garden snail, Cornu aspersa. Banded snails, Cepaea species, which are a little smaller and often brightly banded yellow, white and brown, may also be numerous, but these are much less damaging to plants.
Snails are most active after dark or in wet weather, and the tell-tale slime trails, if present, will alert you to the level of activity.
Snails eat a wide range of vegetables and ornamental plants, especially seedlings and other soft growth. Most damage is done in spring by snails feeding on seedlings, new shoots and plant crowns.
You may see the following symptoms:
- Snails sometimes leave behind slime trails, which can be seen as a silvery deposit on leaves, stems, soil and hard surfaces
- Snails make irregular holes in plant tissues with their rasping mouthparts. Young shoots and leaves are damaged or eaten, not only at ground level but often high up
Snails are so abundant in gardens that some damage has to be tolerated. They cannot be eradicated so target control measures on protecting the more vulnerable plants, such as hostas, seedlings and soft young shoots on herbaceous plants.
There are various measures you can take:
- Transplant sturdy plantlets grown on in pots, rather than young vulnerable seedlings. Protect transplants with plastic bottle cloches
- Encourage predators such as thrushes, toads, hedgehogs and ground beetles. The nematode (‘Nemaslug’), Phasmarhabditis hermaphrodita, used to control slugs in the soil is unlikely to control snails, since they spend most of their time at or above soil level
- Place traps, such as scooped-out half orange, grapefruit or melon skins, laid cut side down near vulnerable plants, or jam jars part-filled with beer and sunk into the soil. Check these and empty them regularly, preferably every morning. Proprietary traps and barriers are available from garden centres
- Barriers made of crushed rocks (Westland Earth Matters Slug Blocker Granules, Growing Success Slug Stop, Vitax Slug Off) can be placed round vulnerable plants, as can repellent gels (Doff Slug Defence Gel, Westland Earth Matters Slug Blocker Gel). Copper tape (Vitax Copper Slug Tape, Agralan Copper Slug Tape, Growing Success Slug Barrier Tape) can be put round pots, or the pots can be stood on copper-impregnated mats (Slug and Snail Shocka, Agralan Slug and Weed Mat)
- Go out with a torch on mild evenings, especially when the weather is damp, and hand-pick snails into a container. Then, either take them to a field, hedgerow or patch of waste ground well away from gardens, or destroy them in hot water or a strong salt solution
- In winter turn over likely hiding places and expose snails for thrushes to feed on
When snails are active, slug pellets containing metaldehyde (Scotts Slug Clear Advanced Pellets, Bio Slug and Snail Killer Pellets, Westland Eraza Slug & Snail Pellets, Doff Advanced Slug Killer or Doff Slug Killer Blue Mini-pellets) can be used to protect vulnerable plants, particularly seedlings and newly emerged shoots of herbaceous plants. These pellets can harm other wildlife, pets and young children if eaten in quantity; pellets must always be scattered thinly around the plants.
Pelleted baits, containing ferric phosphate, (Growing Success Advanced Slug Killer, Bayer Organic Slug Bait, Vitax Slug Death XL) are relatively non-toxic to vertebrate animals.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Snails and slugs cause similar damage and can climb, often to a considerable height, above ground level. Because of the protection provided by their shells, snails can move more freely over dry terrain than slugs.
Snails are less common than slugs where acid soils prevail and, unlike slugs, they remain dormant over winter, often clustering together under empty upturned flower pots, stones or other protected places.
Reproduction occurs mainly in autumn and spring, when clusters of spherical, yellowish-white eggs can be found under logs, stones and pots.
Common name Snail
Scientific name Various, but mainly Cornu aspersa
Plants affected Many ornamental plants and vegetables in gardens and greenhouses
Main symptoms Holes in foliage and flowers
Most active Spring to autumn