Plants affected
A wide range of vegetables and ornamental
plants, especially seedlings and other soft growth.
Symptoms
Young tender shoots and leaves are damaged or eaten, not only at ground level but often high up. Slime trails are sometimes seen near where snails have been active. See also Slugs.
Cause
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. The snail most commonly encountered in gardens is the common garden snail, Helix 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 less damaging to plants.
Slugs and snails are most active after dark or in wet weather. Reproduction occurs mainly in autumn and spring, when clusters of spherical, yellowish-white eggs can be found under logs, stones and pots.
Control methods
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 and young vegetable plants.
There are a number of non-chemical and chemical controls you can choose.
Non-chemical
control
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.
There is also a range of proprietary traps and barriers
available from garden centres.
- Barriers made of crushed rocks (Fito Slug Stoppa, Growing Success Slug Stop, Vitax Slug Off, Gem Slug n Snail Repellent) can be placed round vulnerable plants, as can repellent gels (Greenfingers Slug Defence Gel, Westland Slug Blocker Eco Barrier Gel. Copper tape (Fito Slug Stoppa Tape, Agralan Copper Slug Tape, Growing Success Slug Barrier Tape) can be put round pots, or they 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, if you can, 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.
Chemical control
When snails are active, slug pellets containing metaldehyde (Scotts Slug Clear Advanced Pellets, Bio Slug and Snail Killer Pellets, Gem Superslug Killer, Westland Slug Buster Pellets, Westland Slug Attack Mini-pellets, Doff Advanced Slug Killer or Doff Slugoids Slug Killer) 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.
Slug killers based on aluminium sulphate (such as Doff Slug Attack) are less toxic and can be used as an alternative, particularly in the spring against newly hatched snails.
A relatively new type of pelleted bait, containing ferric phosphate (Growing Success Advanced Slug Killer) is relatively non-toxic to vertebrate animals.