Slug life

Chief Horticulturist Guy Barter dishes the dirt on this most troublesome of garden pests

Slug on lettuce

Why us?

Atlantic Europe with its mild temperatures and moist weather is ideal for slugs, so it is no surprise that they are amongst the most damaging UK pests. Bitter continental climates where the soil freezes deeply or regions with hot dry seasons are relatively slug free.

Year of the slug

Typically, slugs become inactive in winter and populations decline. Removing debris, weeds and other shelter so birds and weather can get at them help depress slug numbers.

In spring they resume feeding and breeding. New leaves and seedlings cannot tolerate much damage. Raking and hoeing to remove shelter can usefully suppress slugs in the dry windy weather so common in spring.

In very dry summers their population and activity are suppressed, but in warm wet weather they multiply rapidly.  Fortunately, many garden plants can usually tolerate a fair amount of grazing once they have matured and become fully grown. Slugs are gastropods (the name comes from the Greek words for stomach and foot) and so are related to snails, limpets and whelks.

When they eat useful parts of plants, potatoes and strawberries for example, action has to be taken. Warm moist soils make ideal conditions for gardeners to apply slug-killing nematodes. Nematodes leave no residues in food so can be used in strawberries and salads close to harvest.

By autumn slugs are on the decline and do little damage to mature plants.  Farmers grow many autumn-sown crops which are highly vulnerable unless pelleted but in gardens most sowing is done in spring at the lowest point in the annual sluggy cycle.

Advert for Celerite Slug Powder. From 'Popular Gardening' (April 24, 1937)Control methods

Slug pellets have long provided good control but like all pesticides, their use should be minimised and only used when other methods fail.  Metaldehyde (traditionally the most commonly-used active ingredient) has been withdrawn due to its poor environmental impact, but ferric phosphate pellets remain available, and are certified for organic use.

Recent RHS research has found that barriers, grit or other sharp materials, are not reliable although you will find many gardeners who swear by them.

Friendly Slug (Testacella), 'A handbook for young gardeners' (1928)Friends after all?

Surprisingly some slugs are useful to gardeners – the RHS is supporting research into these.

See also

RHS Slug Advice

Find out more about biological pest controls

See also

Gardeners' calendar

Find out what to do this month with our gardeners' calendar

Advice from the RHS

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