Winning the slug war.

Winning the gastropod battle without chemical weapons

The enemy

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:

1. Use slug pellets wisely, and before use, always read the instructions on the pack.

2. 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.

3. Individual pellets should be placed 10 – 15cm apart around the plant. Never pile them.  

4. Always secure the container and store safely out of reach of children and pets.

5. 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?

Feeding the hedgehog too much might stop them eating the slugs!

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!

Frogs will be attracted even to a very small pond

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. 

This dahlia cutting had been almost obliterated by slugs and snails, but has recovered well on the matting

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!