Winning the gastropod battle without chemical weapons
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The
enemy
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Every gardener
loathes the damage done by slugs and snails (gastropods). They seem
to delight in demolishing our most cherished flowers and vegetables
at just the wrong moment. With the frustration that this causes, it
can be no wonder that many gardeners reach for the slug pellets, but
I'm hoping this post can persuade some people to stop and consider
some alternatives.
Slugs and snails
do perform an important function in the environment – they break
down dead and dying organic matter which frees up vital nutrients
such as nitrogen to improve the soil. Not all species of slugs and
snails are a problem for gardeners but the Garden Snail, the Garden
Slug, the Field Slug and the Keel Slug can wreak havoc in gardens so
I won't try to argue to live and let live!
What's wrong
with pellets?
There are many
debates about just how harmful slug pellets are. There are several
types of pellet methiocarb, metaldehyde (the most
common) and those that contain ferric or aluminium compounds.
Methiocarb
is about 10 times more toxic than metaldehyde and will be banned in
Slug pellets from September 2014, so fortunately won't be an option
for gardeners or commercial growers from now on.
Metaldehyde
is undoubtedly harmful to pets, children and wildlife if they consume
the actual pellets in sufficient quantity so following the
instructions and not using too many, or in inappropriate places is
vital. Mammals such as hedgehogs and birds might eat the pellets –
since they contain wheat to attract the slugs. Some pellets have
bright blue colouring or bad tastes, but this might not be enough to
stop something unintended eating them. The effects of metaldehyde on
animals that eat poisoned slugs or snails is more controversial.
However predators may well prefer to fill up on the dead or dying
slugs (because they dry out) than others that are not poisoned. Put
simply, if you poison some slugs, then the rest will survive longer!
Aluminium
sulphate, ferric sulphate
or ferric phosphate
products are often
labelled as organic and “won't harm pets and wildlife” because
those substances are regarded as relatively harmless. They maybe the
least harmful option. However, there may be more to the issue because
they sometimes contain other ingredients such as EDDS or EDTA which
might not be so benign (see links here
and here)
Ultimately,
wildlife organisations such as the WildlifeTrust and the RSPB
discourage the use of chemical controls in the garden.
The RSPB encourages all gardeners to use non-chemical forms of slug control as much as possible. However, in the event of all non-chemical solutions being unsuitable or impractical, the RSPB welcomes and endorses the 'The Slug Pellet Code'. The code is as follows:
Use slug pellets wisely, and before use, always read the instructions on the pack.
It is essential that slug pellets are sprinkled thinly on the soil and around the plants being protected – not all plants are favoured by slugs and snails.
Individual pellets should be placed 10 – 15cm apart around the plant. Never pile them.
Always secure the container and store safely out of reach of children and pets.
Always use and store slug pellets wisely.
In any case, slug
pellets are far from a perfect solution for protecting your plants –
some slugs and snails may not eat them at all, they are unsightly and
the pellets will disintegrate with rain & time.
Non-chemical
control methods
A
simple but effective method of reducing your slug and snail
population is cultivation. Turning over the soil can bring
eggs to the surface causing them to dry out and allowing them to be
eaten by predators. Of course, this is more practical on an allotment
than in most gardens.
Encouraging
predators should
be a goal for every gardener. Slugs are
eaten by rove beetles (such as the devil's coach horse), ground
beetles, centipedes, slow worms, frogs, toads and even mice.
Apparently glow-worms and their larvae also prey on slugs and snails
– who wouldn't want them?
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Feeding
the hedgehog too much might stop them eating the slugs!
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Hedgehogs
have a reputation for eating slugs, though perhaps they only form
about 5-10% of their diet. The hedgehogs in my garden certainly
ignored most of the slugs that were attracted to the feeding bowl and
preferred to tuck into the food I supplied. Even so, they're great to
see in your garden and you should be helping your hogs by ensuring
they can access your garden through holes in the fence or providing a
safe place to hibernate, or even by feeding them directly. Foxes and
badgers might also polish off a few slugs and snails.
Many
birds will eat slugs, including Tawny Owls as we saw on Springwatch
this year and some, like Blackbirds and Mistle Thrushes will eat
small snails. Song Thrushes are very partial to larger garden snails,
smashing their shells on stone anvils. Sadly, Song Thrushes have
undergone a 54% decline from 1970-2010. Although there has been some
recovery in their numbers, but we need to look after these guys!
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Frogs
will be attracted even to a very small pond
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Frogs
and toads are great predators to have around and should be encouraged
in your garden or allotment. Everyone should have a wildlife pond, no
matter how small, if at all possible. Slow worms and grass snakes
will also be munching a few slugs, so make sure they've got suitable
places to hide if you think you're lucky enough to have some in your
garden.
Guinea
fowl, chickens and especially ducks are supposed to be excellent for
slug control, though of course, domestic animals bring their own
problems.
Nematodes
A
straightforward, if expensive, way to combat slugs is to release
nematodes (tiny worms) which parasitise them. These are a natural
parasite of slugs, so you are not releasing an invasive species. You
can buy packs to cover a relatively large area, eg 40 or 100 m2,
mix them with water in a watering can, and spread them over your
garden or allotment. The nematodes will get to work killing and
disabling the slugs, whilst there is no risk of harming or poisoning
other wildlife. Sadly, the treatment will begin to lose effectiveness
after about 6-8 weeks, but you can reapply it. The packs need to be
refrigerated if you want to store them. It is not the cheapest
solution, but it is worth considering. You can buy it here. It is
recommended to wait until the temperature is over 5ºC for it to
work.
Barriers
Diatomaceous
earth, ash or fine sawdust have been suggested as substances which
absorb slime, drying out the culprits. However rain or wind can
quickly thin these out making them less effective. Other substances
are supposed to be unpleasant for the slugs and snails to cross –
human or animal hair, crushed eggshells or sharp sand (make sure it
has no cement in it!). These may not be that convenient or
attractive, and their effectiveness is variable. It is possible to
buy wool pellets which swell and form a barrier.
One
solution that works well and is more appealing is to use a copper
barrier. The slugs and snails get a shock if their slimy foot touches
the copper and and so avoid crossing the metal. Sticky copper tape is
widely available which you can put around your pots. Copper feet are
available as pot stands and work in the same way. I have seen copper
barriers available in the USA, but not on sale in the UK as far as I
know.
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This
dahlia cutting had been almost obliterated by slugs and snails,
but has recovered well on the matting
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Copper-impregnated fabric is a good way to protect pots or trays of
seedlings. You can also cut small star-shaped holes and plant
seedlings through the fabric, which might be good for delicate
vegetables. Snail and slug matting is available from eBay (Slug matting). The matting is reusable and although it seems
expensive, it can be worth it to save your lovingly tended plants
whilst leaving your garden looking good.
Of
course with these barrier methods its important to check the pot or
area for slugs and snails before you use them. Otherwise you are
trapping the culprits in, not out! Overhanging or dead leaves can
form a way over any types of barriers so you may need to check on
your plants as they grow.
Traps
Slug
beer traps are an age old solution and do indeed manage to kill a
few. They're simple to make, just sink a yogurt pot into the ground
but make sure to leave about 2cm left above soil level to prevent
beneficial beetles falling in. You might want to cover it to keep
the rain out, leaving a gap for the slugs and snails to enter.
Apparently Budweiser is one of the best brews for slug trapping but
even non-alcoholic beers can be just as good. Much more cheaply, you
can also use your own home brew mixture or even just
yeast/sugar/flour. Apparently cabbage soaked in washing up water or
even grapefruit juice can work too.
If
you prefer a trap that you don't need to bury in the ground, the
Slug-X trap has been recommended.
Traps
will only deal with a small percentage of the slug and snail
population though so don't expect miracle protection for your plants.
The worst aspect is having to empty the traps, which after a few days
becomes an unpleasant task. At least you will feel you are making some dent in the enemy numbers.
Manual
Collection
Human
beings are one of the most effective creatures at controlling slugs
and snails, but we're not so good at finding them in their hideouts.
All sorts of things can be left as refuges for slugs and snails to
hide under or you can put out some bait – oatmeal or bran works
well. Once you get them in one place they're easy to collect and
kill.
Salt
will kill slugs and snails on contact. Some people feel this is
rather cruel, moreover, it may not be good for your soil to put large
amounts of salt on your garden or allotment. Collecting
them is best done in early evening just after dusk, and you'll
probably find more in damp conditions.
Although
it's fairly hard work, a few hours effort spread over several nights
can dispose of many of the larger slugs and snails. You could even
eat the Garden Snails!
There
are books written on the subject of organic slug control such as
BanishSlugs by Jeremy Stratton. Trial and error is often needed as
every circumstance is different. What works really well for some
people may be useless for others, and vice versa. Ultimately, without
using pellets, a combination of methods might not win the war, but
you should get you to some kind of acceptable cease-fire.
Good
luck and try not to get too obsessive with winning this battle!
