Garden Pests

Slugs and Snails

"The further off from England, the nearer is to France. Then turn not pale, beloved snail, but come and join the dance."
Lewis Carroll

Nature of the Problem

Slugs and snails are the bane of most gardeners. Whatever measures you take, you cannot eliminate them or, if you think you have, they soon return with a vengeance.

It's not so much that gardeners have a downer on the creatures themselves. It's the damage they do to garden plants – damage that disfigures those plants we grow for their appearance and stunts those we grow for food.

In fact, slugs and snails are probably less prone to damaging our prize plants than we may think. For the most part, their preferred diet is decaying plant material, which is a good thing. It is when there is insufficient decaying material that they turn their attention to soft healthy plants – which is perhaps understandable really!

This is why you will often find slugs in the compost bin, where they have a feast on the waste material you are recycling. They are probably not doing much harm in the compost and at least they are not eating your prize plants.

The downside is that they will leave their eggs behind in the recycled material that you plan to spread on your garden. One way to control this is to wait until the compost is ready for use and then spread it out on a hard surface for a few days, which gives the birds an opportunity to find and consume the eggs for you.

Reproduction and Lifestyle

Slugs and snails like to hide away in cool, damp places where they are safe from predators (which includes gardeners). You will typically find them amongst decaying plants, under stones, boards, pots or anywhere that offers protection from sun, rain and wind.

Because they are vulnerable to anything that causes them to lose moisture, slugs in particular prefer to hide during the day and feed after sunset.

Although they like moist places, slugs hate rain and will find shelter. However, once the rain ceases, the conditions are ideal for them to go on a feeding frenzy.

Slugs have no shell (or very small shells in some cases) and no bones so that they are able to secrete themselves in very narrow crevices.

Whilst snails are able to survive through winter by withdrawing into their shells and hibernating, snails don't have such protection and are therefore less likely to survive, other than as eggs.

If your garden is already infested with snails or slugs, then you will want to find ways of removing them. However, the best approach is to discourage them in the first place or at least discourage them from damaging your plants.

Consequently, we first look at methods for prevention and then how to remove them.

Deterrents

You are unlikely to completely rid your garden of these pests, but there are some precautions you can take to minimise their colonisation.

Hiding Places

Taking account of their favourite hiding places, it helps if you can deny them such opportunities. To do this completely would mean having no garden at all, which would be self-defeating. However, you can at least remove unnecessary rubbish from your garden and keep it reasonably tidy.

Slugs lay their eggs in soil where many survive the most severe winters. Where you are able, it is worth digging over or hoeing bare soil before the winter sets in. This gives predators an opportunity to find and eat the eggs.

Barriers

In theory at least, slugs and snails don't like crawling over anything that is dry and scratchy. Consequently you can give some protection for vulnerable plants by providing barriers around them.

Materials that have been suggested for this purpose include:

• Eggshells that are crushed fine
• Ash from burned wood – again crushed fine
• Coarse sand or gravel – the sharper the better

Whilst such barriers may have an effect, the downside is that they are easily breached by rain or wind. They can also be disturbed by other garden visitors, including worms that take the material down into the soil. Once the first gap appears they no longer provide any effective protection.

Consequently, to maintain their effectiveness, it is necessary to inspect them regularly and repair any gaps as soon as they appear.

Another form of barrier is copper in various forms. The theory is that when slugs and snails attempt to cross copper, they generate a mild electric shock, which deters them.

Designs of copper rings are available commercially but are significantly more expensive than some of the other deterrents. Consequently, you may only be able to use this method for particularly important plants.

Of course, all your efforts are wasted if you then import more slugs from elsewhere. For this reason it is always worth inspecting new plants for signs of slugs, snails or their eggs.

Getting rid of slugs and snails

Many methods have been advocated for getting rid of slugs and snails. They roughly fall into the following categories.

• Predators
• Mechanical
• Chemical
• Organic

Not all of these methods are appropriate for all situations and therefore gardeners need to consider those that are suitable for their gardens and their own personal preferences. If possible it is good if you can employ a number of methods in combination.

Predators

There are many common visitors to your garden that enjoy feasting on slugs and snails including for example:

Birds

There's a variety of things you can do to entice birds to regularly visit or even take up residence in your garden. A bird table with scraps and various bird feeders will attract birds in the first place. Good nesting sites also help, such as dense hedges or purpose built nesting boxes.

Hedgehogs

Hedgehogs need places to hibernate over winter so you need to provide suitable accommodation such as log piles or mounds of dried leaves. If you want to feed hedgehogs, then dog or cat food is the best option, but ensure it is being taken by preferred visitors since you may inadvertently be attracting rodents. There is a false idea that hedgehogs like bread and milk but this is a mistake and can actually do more harm than good.

Frogs, Toads and Newts

These creatures all need water, though they spend most of their time on land. Consequently, a small pond is ideal if it is easy to get in and out. Generally being nocturnal creatures, you also need to provide shelter for them during the day by way of dense plant cover or piles of rocks and stones.

Shrews

Shrews live on a diet of worms and insects as well as slugs and snails. They generally like to burrow to make a home so you need to take this into account especially if you have a small garden and are not able to set aside an area that is uncultivated.

There are other natural wild predators but these are probably the most common and effective.

In addition to wild creatures, many people claim that ducks, geese or chickens are an effective means of controlling slugs. Unfortunately they can make their own mess of the garden so they may not be your first choice unless you have other reasons for keeping them. The major drawback with such livestock is that you need effective defences against foxes.

Mechanical

By this we mean physically hunting and removing individual slugs and snails. For example, it is worth watching for adults or eggs whenever you are digging over the soil. Simply leaving them exposed may be sufficient to attract birds to do the work for you.

It is surprising how effective you can be in controlling slugs and snails by hand picking them and then disposing of them. It helps if you can entice them to gather together so you don't need to do so much hunting.

You can encourage slugs and snails to congregate together by placing "traps" around the garden in the form of flat pieces of wood, slate, stone or similar materials that provide a "safe" place for the creatures to hide during the day. They don't need to be large – perhaps six inches to a foot across should be sufficient. Upturned pots are also effective for this purpose. Use small stones to prop them up and so provide a means of entry. Lift the traps each morning and dispose of anything that is hiding there.

Traps can also be created from small pots (e.g. yogurt pots) that are sunk into the ground so that their rim is level with or slightly higher than the soil. You can buy containers specially made for this purpose. Fill with beer, which attracts the slugs and drowns them. It doesn't matter if the beer is out of date since it is just as effective for this purpose. If you don't have beer then any sweet sugary drink will do.

When conditions are right, slugs and snails are most active around two to three hours after sunset and therefore, this can be a good time to locate and destroy them. Bear in mind, however, that they dislike rain and strong wind so will not emerge until conditions improve.

How you choose to dispose of dead slugs and snails depends on your personal preferences but it is worth remembering that they are a favourite delicacy of many birds.

Poisoning

Slug pellets is perhaps the most popular method for controlling slugs and snails, and it is certainly effective, though it has a number of serious drawbacks. The pellets can contain a variety of chemicals, some of which are more water resistant than others. Those containing metaldehyde are easily available, not very expensive and appear to be most effective.

You need to take care in using any kind of poison, particularly since they are not particularly selective and can affect other life forms, causing severe sickness or even death. It is vital, therefore, to read and follow the instructions carefully. You may even harm other life forms that eat the dead slugs and snails because of the residual poison in their bodies.

If you have pets or young children that like to test everything by putting it in their mouths, then this method is definitely not recommended.

One option to reduce the effect on other creatures is to use the pellets in conjunction with "traps" as mentioned above so that they will be found by slugs and snails that are seeking shelter after they return from feeding. However, this precaution may not be sufficient to protect curious children from being poisoned.

Organic or Biological

Many gardeners prefer to use nature's own methods to keep pests under control and there are biological methods that are particularly helpful for destroying small slugs that live under the soil where they may not be obvious to most other predators.

There are various small worm-like creatures known as nematodes that are useful against garden pests. In particular, Phasmarhabditis Hermaphrodita attack slugs and snails and kill them by laying their eggs inside them. These need to be applied every few weeks by watering them into the soil or by applying them in a powder form.

Although this can be a relatively expensive option, the great benefit of this form of control is that you are not harming any other creatures or damaging the environment.