Slugs and Snails Gastropoda

Look for

Slugs and snails feed at night and are easy to spot. They leave behind unmistakeable silvery slime trails and decimated young plants, leaves and flower buds. During the day they tend to gravitate to dark, moist areas of the garden and greenhouse, or hide on the undersides of large leaves and under pots.

Plants affected

• They feed on a wide range of plants and cause severe damage as they rasp or chew away on leaves, stems, roots, bulbs, tubers, buds, flowers and fruit with their toothed tongue.

About Slugs/Snails

• Slugs and snails are collectively known as garden molluscs.
• Slugs and snails have many similarities since slugs have actually evolved from snails. Their external shell has been replaced by an internal plate that protects their lungs.
• Both are soft-bodied and move using a large muscular foot that slides over a slimy secretion.
• They have two pairs of tentacles, the lower for smelling and the upper for seeing.
• Noted for elaborate courtship and mating rituals, they can lay up to 500 eggs during adulthood. Snails can often be seen joined together whilst mating.
• The field slug, Deroceras reticulatum, this is generally the most damaging slug. It's 3cm to 4cm in length and can be various colours from grey to fawn. It feeds mainly above ground.
• The garden slug, Arion hortensis, a dark grey to black slug, up to 4cm long. It feeds above and below ground.
• Keeled slugs, Milax spp, there are many different species, all are dark grey, brown or black and up to 10cm long and with a distinct ridge or keel running down the back. They live in soil but also feed above ground.
• Common snail, Helix aspersa, these have a grey-brown shell with darker bands. They are often found near walls, in rockeries and in overgrown herbaceous borders. Snails can live for several years, hibernating in clusters, in dry holes in walls and so on.
• Round-backed black or brown slugs, Arion ater, these feed on rotting vegetation and therefore don't require controlling.

Treatment

Chemical

Products containing the following chemical ingredients are all effective on Slugs/Snails

• Metaldehyde
• Methiocarb
• Copper sulphate
• Ferrous phosphate
• Aluminium sulphate

Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.

Organic

• Attract slugs and snails by leaving out decaying organic matter, such as lettuce leaves or grapefruit skins. Inspect these after dark then collect and kill molluscs by dropping them into a bucket of salty water.
• Use copper rings around the base of susceptible plants - these repel molluscs by generating a small electric current.
• Sink shallow dishes (or purpose-built slug and snail traps) filled with beer to soil level. Slugs and snails are attracted to the beer, become intoxicated and drown.
• Sprinkle ashes, soot, sharp sand, crushed nut or eggshells around plants to provide a physical barrier that slugs and snails don't like to cross.
• You can buy live nematodes, Phasmarhabditis hermaphrodita, commercially. Drench infested areas with this tiny worm which burrows into the body of the slug and infects it with bacteria which kill it. These nematodes aren't effective against snails.
• Grow plants with rough or hairy leaves which are less palatable or use some young plants as sacrificial specimens in order to discourage the slugs and snails from your favourites.
• Products containing Ferrous phosphate are acceptable for Organic gardeners as they do not harm other wildlife or contaminate the soil.

Prevention

• Cultivate growing areas frequently to expose eggs, young and adults to predators such as birds, frogs and hedgehogs.
• Limit the use of organic composts and mulches around plants, because they're particularly attractive to slugs.
• Remove objects from growing areas that molluscs can use as daytime refuges, such as logs and large stones.
• Encourage natural enemies such as beetles and centipedes by providing overwintering refuges in the autumn.
• Check your flower beds, pots and lawns at night using a torch and collect the slugs and snails that will be searching around for food.