Chief Horticulturist Guy Barter dishes the dirt on this most troublesome of garden pests
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.
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 Metaldehyde (traditionally the most commonly-used active ingredient) has been withdrawn due to its poor environmental impact, but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.
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
