What are snails?

Snails are gastropods; single-shelled, soft-bodied animals in the molluscs group of animals. Snails, along with slugs, use their rasping tongues to eat holes in leaves, stems and flowers of many plants. There are many control options available for slugs and snails but despite this they remain a persistent pest. The RHS is carrying out a scheme of research on gastropod control methods to improve the advice we can give to home gardeners.

The snail most commonly encountered in gardens is the common garden snail, Cornu aspersum. 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, can alert you to the level of activity.

Snails eat a wide range of vegetables and ornamental plants, especially seedlings and other soft growth. They are good climbers and can be found high up in some plants. Most damage is done in spring by snails feeding on seedlings, new shoots and plant crowns. Snails will also eat decomposing organic matter such as rotting leaves, dung and even dead slugs and snails.

Symptoms

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

Control

Snails are often 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, vegetables and soft young shoots on herbaceous plants.

Non-chemical control

There are many preventive measures that have been used by gardeners to minimise snail damage. Most of these do not have any scientific evidence to prove that they are effective. These measures include:

• Transplanting sturdy plantlets grown on in pots, rather than young vulnerable seedlings. Transplants can be given some protection with cloches
• Torchlight searches on mild evenings, especially when the weather is damp; hand-picking snails into a container. They can then be taken to a field, hedgerow or patch of waste ground well away from gardens, or killed in the freezer before being added to the compost heap or put in the bin
• Some birds, frogs, toads, hedgehogs, slow-worms and ground beetles eat slugs and snails and these predators should be encouraged in gardens
• Raking over soil and removing fallen leaves during winter can allow birds to eat slug eggs that have been exposed
• Traps, such as scooped out half orange, grapefruit or melon skins, can be laid cut side down, or jars part-filled with beer and sunk into the soil near vulnerable plants. Check and empty these regularly, preferably every morning. Proprietary traps are also available from garden centres and mail order suppliers
• Barriers, thought to repel snails, include rough or sharp textured mulches and substances thought to be distasteful or strong smelling. Copper-base barriers have been shown to repel slugs in some studies. A recent RHS study in a garden-realistic scenario however, found no reduction in slug damage from barriers made of copper tape, bark mulch, eggshells, sharp grit or wool pellets

Most of these non-chemical control options have very little scientific research into them, but the RHS is hoping to address this knowledge gap and is carrying out a range of scientific studies.

The nematode biological control available to control slugs is unlikely to affect snails, as they rarely come into contact with the soil-dwelling nematodes.

Pesticides

Following the manufactures instructions scatter slug pellets thinly around vulnerable plants, such as seedlings, vegetables and young shoots on herbaceous plants. It is important store pellets safely and scatter them thinly as they can harm other wildlife, pets and young children if eaten in quantity.

There are two types of slug pellet approved for use in gardens, those based on metaldehyde and those based on ferric phosphate. Ferric phosphate based pellets are approved for use by organic growers. Products include Growing Success Advanced Slug Killer, Solabiol Garden Slug Killer, Vitax Slug Rid, Doff Super Slug Killer, Sluggo Slug & Snail Killer and SlugClear Ultra3. To protect children and pets pellets must be used as directed. Products for home garden use containing metaldehyde include: Ultimate Slug and Snail Killer, Deadfast Slug Killer, Doff Slug Killer Blue Mini Pellets, Westland Eraza Slug and Snail Killer.

Metaldehyde ban 
In December 2018 DEFRA announced that metaldehyde will be banned from most uses in Spring 2020.The ban included all home garden use. This decision was overturned in July 2019, based on a legal challenge to the process by which the ban was put in place. This means that metaldehyde slug pellets are still available for sale and legal to use. However it is likely that a new ban will come through at some point in the future. The original decision followed advice from the UK expert committee on Pesticide and the Health and Safety Executive (HSE) who considered that metaldehyde poses an unacceptable risk to birds and mammals. 

Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Most plants, once established, will tolerate some slug damage and control measures can be discontinued. The RHS is researching sustainable control options for slugs and snails.

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

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.

Some plants less likely to be eaten by snails

Some herbaceous plants are less likely to be eaten by slugs and snails, these are listed below

Acanthus mollis (bear's breeches)
Achillea filipendulina
Agapanthus hybrids and cultivars
Alchemilla mollis (lady's mantle)
Anemone × hybrida (Japanese anemone), A. hupehensis (Japanese anemone)
Antirrhinum majus (snapdragon)
Aquilegia species
Armeria species
Aster amellus, A.× frikartii, A. novae-angliae (Michaelmas daisies)
Astilbe × arendsii
Astrantia major
Bergenia (elephant's ears)
Centaurea dealbata, C. montana
Corydalis lutea
Cynara cardunculus (globe artichoke)
Dicentra spectabilis (bleeding heart)
Digitalis purpurea (foxglove)
Eryngium species
Euphorbia species (spurges)
Foeniculum vulgare (fennel)
Fuchsia cultivars
Gaillardia aristata
Geranium species
Geum chiloense
Hemerocallis cultivars (day lilies)
Papaver nudicaule (Iceland poppy)
Pelargonium
Phlox paniculata
Physostegia virginiana (obedient plant)
Polemonium foliosissimum
Polygonum species
Potentilla hybrids and cultivars
Pulmonaria species (lungwort)
Rudbeckia fulgida
Salvia × superba
Saxifraga × urbium (London pride)
Scabiosa caucasica (scabious)
Sedum spectabile (ice plant)
Sempervivum species (houseleeks)
Sisyrinchium species
Solidago species (golden rod)
Stachys macrantha
Tanacetum coccineum (pyrethrum)
Thalictrum aquilegiifolium
Tradescantia virginiana
Tropaeolum species (nasturtium)
Verbascum species (mullein)