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All gardeners spend the warm,
wet Welsh summer doing battle with slugs, but organic
gardeners shouldn’t resort to slug pellets to save
their plants as they can pose a risk to other wildlife.
This article gives some ideas for natural alternative
solutions to try instead. There are thirty different types
of slug in Britain. The most common, and those whish do
the most damage, are the grey field slug, the garden slug,
the keel slug and the black slug. The grey field slug,
Deroceras reticulatum, was once prescribed as a cure for
consumption and either swallowed live or boiled in milk.
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A single slug can lay up to five hundred eggs each year. They
can over-winter and become active again as soon as conditions
become mild and damp in the spring. Slug pellets are cereal
chunks containing poison, such as metaldehyde. The cereal bait
can also be attractive to other wildlife and pets. There is
also the danger of a predator, such as a hedgehog, eating poisoned
slugs. Metaldehyde has been reported as affecting the fertility
of songbirds. The pellets can therefore cause injury or death
to other animals, even if stored and used correctly. Slug pellets
are banned under Soil Association standards.
Prevention is Better than Cure
Organic gardeners should encourage natural predators so that
the slug population is kept under control. Ground beetles are
very useful as they feed on slug eggs as well as the slugs themselves.
Garden birds such as blackbirds and song thrushes will eat considerable
numbers of slugs, as will frogs and toads. A hedgehog can eat
hundreds of slugs a night. Slowworms, spiders and harvestmen
can eat small slugs. If you keep chickens or ducks, you’ll
find that they also enjoy a meal of mollusc. Hedges, log piles
and compost heaps all provide habitats for these predators –
unfortunately, they can also give cover to slugs…
In the vegetable patch, some crop varieties are more attractive
than others to slugs. Garlic, onions and chives between crops
might help deter them. Planting a lavender bush border and keeping
the patch weeded might also help. Slugs thrive in damp gardens
with plenty of vegetation to provide cover and aid movement.
Adding sand to the soil in ‘sluggy’ sites can help
improve drainage. Slugs find fine, firm soil more difficult
to cross and there will be fewer air spaces that slugs can use
as shelter.
Flowers that seem less attractive to slugs include busy-lizzies,
foxgloves, hollyhocks, lavateras, forget-me-not, alliums, rosemary,
wallflowers, lavender, phlox, columbine, snapdragons, geranium,
tulips and hydrangea. Water your garden in the early morning
rather than in the evening, when slugs are just becoming active,
as the moisture attracts them and helps them move around.
Declaring War
There are various methods of slug control that gardeners employ,
with varying degrees of success. On a small scale, traditional
beer traps are very effective at drowning slugs, but other invertebrates
might also be caught. Traps can be made easily by recycling
large, lidded, plastic yoghurt pots. Wash the empty pots and
dry. Cut two slug-sized holes on either side, 1 cm down from
the rim. Sink into the soil to the level of these holes. Fill
with beer (or grape juice) to a depth of 2cm. Replace the lid
to stop rain getting in. Empty each morning and top up the liquid.
Barrier methods can be used to stop slugs getting to plants
in pots. Petroleum jelly can be smeared on the rim or copper
tape stuck around the edge. This has a small electrical charge
that repels slugs. Broken eggshells, ash and salt can also be
effective barriers. Slugs are said to dislike the smell of pine,
so borders could be made with pinecones.
Oatmeal and bran are very appetising to slugs, but kill them.
Horse bran can be bought cheaply in large sacks to spread over
vegetable patches. Other methods are more direct and immediate.
Mowing the lawn at dusk will cut up slugs. Night patrols with
a kitchen knife or scissors and a bucket for the carcasses can
be very effective if you have the stomach for the job! Competitive
small children could be given pocket money for the number of
slugs they collect and drown. Nematodes,
such as Phasmorhabditis hermaphrodita, are a biological control
agent that can be very effective in reducing an established
slug population. The eggs are watered into the soil where
they hatch, search out and infect slugs with bacteria, preventing
them from feeding. The slug dies within ten days while the
nematodes reproduce inside the body, ready to find new victims.
In the future, a wildlife-friendly slug pellet might be available
which will be safe to use in gardens. The Research Institute
for Organic Agriculture in Switzerland is developing a pellet
based on iron phosphate, which is not toxic to animals. This
might finally be the answer we’ve all been waiting for!
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