Slugs - how to control them
The most commonly used form of slug control is slug pellets, which contain one of two poisons – metaldehyde or methiocarb.
These are poisonous to many animals and each year there are incidents of domestic pets dying from poisoning. Hedgehogs are particularly vulnerable because they eat dozens of slugs each night and the poison builds up to lethal concentrations.
To control slugs it helps to know a little about them and their habits.
Slugs are molluscs and are not able to control water loss from their bodies, so they must shelter in damp places during the day and come out to feed at night.
Once a slug has located a good food source, it returns to it by picking up the previous night’s slime trail. Slugs are most active in spring or early summer, when plants are at their most vulnerable.
Although it might seem as if every slug (and snail) is out to destroy your treasured plants, many simply clear up dead or rotting material or feed on fungi and lichens.
Below are some hints and tips on how to cope with slugs without having to use poisonous chemicals. There is no single magic formula that guarantees success, but by combining some of the techniques it is possible to keep their numbers down.
Let predators eat your slugs
Encourage wildlife into your garden – birds, frogs and toads, centipedes, beetles and hedgehogs all eat slugs.
Set traps
Containers baited with beer, milk or grape juice kill slugs. They are attracted to the smell, fall in and drown. Slug traps with rainproof clip-on lids are available to buy or you can easily make your own out of old yoghurt cartons or jam jars. Leave the rim of the container about 2 cm above the level of the soil so that slug-eating beetles do not fall in. In rainy weather the liquids can be diluted and may need replacing, or a ‘roof’ can be propped up on small stones.
Hand picking
A trip to the garden after dark with a torch can yield huge numbers of slugs. Use gloves or kitchen tongs if you prefer. Concentrate on vulnerable areas such as new lettuce plants.
Provide refuges
Grapefruit or melon skins, or planks of wood provide excellent cover for slugs to hide during the day. Use these around susceptible plants, check them daily and collect up the slugs.
The comfrey method
Heap up wilting comfrey leaves (which slugs love) in the centre of a bed a week before sowing. Leave for five days, after which they will be covered in slugs. Remove the slugs and then check for two more nights. Compost the comfrey at the end of the week. Finally plant up the bed and surround with a continuous ring of comfrey leaves, which you need to replace regularly. (This method is courtesy of the Centre for Alternative Technology).
This method also works with old lettuce or cabbage leaves covered with a ‘roof’ to stop them drying out. Set them up a week or so before planting out and remove all lurking slugs.
Decoys
Plant alternative food to distract slugs from your vulnerable plants. French marigolds are good decoy plants, and you can clear slugs from them each day.
Create barrier
Cut the bottom off a clear plastic drinks bottle, unscrew the top and use as a cloche over tender young plants.
Change the surface
Surround the base of plants with substances that slugs do not like to crawl over such as gravel, pine needles, ash, crushed eggshell and soot.
Feed bran
Surround vulnerable plants with bran; slugs eat it readily but it causes them to dehydrate.
A good start
Grow plants ‘hard’ and plant into warm soil – sturdy, fast growing plants are more likely to survive. Help seedlings survive by growing them on in pots before planting out.
Choose slug resistant plants
Some plants are less vulnerable to attack by slugs. These include plants that are strongly aromatic, spiny, coloured red or have tough and hairy leaves and stems. Try surrounding vulnerable plants with a ring of resistant plants. Herbs such as chives, sage, lavender, rosemary, and thyme work well.
Allow for loss
Accept that some plants will be lost so plant a few extra to compensate.
Mulching
This provides cover for the predators that eat slugs. Only mulch once the soil has warmed up and plants are growing strongly. Mulching could encourage slugs, so make sure that you don’t mulch small plants or a cold, wet soil.
Creating a tilth
Digging over the ground exposes slugs and their eggs to predators and dry weather or frost. It also breaks up clods and cracks, which can shelter slugs.
Plant in containers
This is useful for slug favourites such as hostas. A band of petroleum jelly around the edge of the pot offers extra protection.
Copper tapes
These are available commercially. The copper reacts with the slime covering the slug, giving them a slight electric shock.
Biological control
Parasitic nematode preparations are available commercially. These are watered on to the soil and can protect an area for up to six weeks. They must be applied to moist soil and above 5ºC.
Environmentally safe products
More products, such as barrier powders and plant extracts, are coming onto the market that claim to be safe and do no harm to the environment. As with all new products, it is important to check what materials they are made from and where they come from, to ensure they are sustainable.
Live and let live!
Remember that we should tolerate a few slugs in our gardens as part of the natural ecosystem.
