Tips on slug control from a landscape architect

As any gardener knows ...

Slugs can cause havoc in your vegetable patch.

The large grey or brown  “Spanish” slug doesn’t have many natural enemies in northern Europe and the UK and loves to eat your seedlings and  plants.

Grey Spanish slug

Here are a few tips on handling a slug problem without using slug poison

Coffee against slugs
Scientist have found out that (liquid) coffee can help to protect your plants against slugs. It should be sprayed on the plants and/or directly on the slugs. It is not yet quite clear how the coffee kills the slugs. Most likely it’s the caffeine it contains which works as a nerve poison. It is certainly worth trying.
The only problem is that heavy rain can dilute the coffee or wash it away.

What are the natural enemies of slugs?
A natural garden with hedges and hiding places for birds, hedgehogs and shrews helps to encourage these natural predators. Blackbirds, starlings and magpies have a big appetite for snails but they have a tough time with the large grey slugs. Hedgehogs kill slugs by rolling over them with their spikes. The problem with Spanish slugs is that they taste quite bitter to hedgehogs. Slugs are also eaten by shrews, moles and toads. Birds and insects which eat slugs eggs too are particularly helpful. Such insects include ground beetles and their larvae and centipedes.

If you got enough space for a duck house, you can raise some Indian runner ducks, but you will need to keep care of them every day. Unfortunately, they make a mess of the garden with their excrement and also tend to eat lettuce.

How do slugs breed?
Slugs are hermaphrodites (there is no male or female). In other words, all slugs can lay eggs and some of them lay up to 800 eggs a year. The eggs look like little white pearls and the slugs hide them under stones, sods of grass and other protected and moist places. The eggs hatch quite quickly in Summer. Eggs laid in Autumn normally survive the Winter to hatch the next Spring.

All slugs need a moist corner to hide in. In the day time, they hide in crevices in the earth and underneath moss, loose stones, paving stones or planks etc. and unfortunately in compost heaps too. Slugs also like to lay their eggs in compost.

What is the best way and the best place to collect and destroy slugs and slug eggs?
Slugs often like to head for your compost heap in the evening, so that’s a good place to look for them. And what do you do when you found them? The popular methods (cutting in half, spreading salt on them) are not very appetizing. The best way to kill slugs is to use boiling water. Of course you must also dispose of the eggs too. One of our customers recommends putting the slugs in the freezer in a plastic bag. This kills them quite quickly.

You can also use a beer trap to catch slugs: Half bury a yoghurt jar and fill it with beer. The slugs are attracted by the beer, fall in and drown. Empty the trap in the morning. You shouldn’t use beer traps regularly since they attract slugs from up to 200 yards away, e.g. from the neighbours.

Another way of catching slugs is to create artificial hiding places, e.g. by putting a wooden plank in your vegetable patch. You can then collect the slugs which are hiding under the plank after a day or two. In Autumn, you can create artificial nests for slugs by digging shallow furrows or crevices in the ground and covering them up with leaves. This makes it easier to find and destroy the eggs.

 Appropriate soil treatment and the use of mulch
Fine soil with plenty of organic matter doesn’t have many cracks where the slugs can lay their eggs. It is best to use garden tools which leave a smooth surface on the soil (such as grubbers and rakes) rather than those that leave deep crevices, such as hoes. It is also a good idea to prepare the soil in late Autumn when the slug eggs have already been laid.

As we have said above, spreading compost and mulch in the garden can actually promote slugs and could even carry slugs into the vegetable patch and provide them with a cosy place to hide during the day. When it’s dark they will come out of hiding and look for anything they can eat.

Accordingly, you should only spread mulch (e.g. grass cuttings) after drying it somewhat and when the soil is fairly dry. You can also use bark mulch around bushes and for flower beds, although it only protects against slugs when it is fairly dry.
The nightly attack can be somewhat reduced by watering your plants in the morning rather than evenings. Try to water just the plants, not the whole bed.

Slugs don’t like eating aromatic plants and herbs. So it is helpful to plant lavender, rosemarine, artemisia, thyme, sage, oregano and hairy plants such as borrage and geraniums which can also be applied to the beds as mulch.

Keeping out slugs with a slug fence
Slug fences are an effective mechanical barrier against slugs and are a long lasting alternative to slug killer, which also poisons the birds and other animals. They are particularly suitable for vegetable patches. The slugs are unable to climb around the double sharp bend at the top of the fence.

The Hanover slug fence is made of galvanized steel (the same material as drain pipes). It is very robust and should normally last for 10 to 15 years.

The following picture shows one of the corner pieces of the Hanover slug fence:

Detail photo of corner piece

Click here for more pictures and more information on slug fences.

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