For many gardeners slugs and snails are the most serious pest. In the organic garden there is no magic cure for slug damage. Effective control means finding what works best for you in your garden.
Ways of combating slugs and snails can be split into 6 main categories:
One way to stop slug damage is to prevent pesky little creatures getting to your plants. A simple way to do that is to cover the plant with a plastic bottle with the bottom cut off and the cap removed. This not only keeps slugs out it also acts as a mini greenhouse.
Surround small beds with a ‘moat’. Trials at Garden Organic of a Square Foot garden surrounded by a moat of plastic guttering filled with water seemed to work OK. A simple version of this is to stand the legs of benches etc in saucer of water.
More Physical barriers:
- Sharp grit
- Crushed egg shells
- Products based on dried clay
- Diatomaceous earth, will need to be replaced after rain
- Wood ash
The use of copper strips round plants stops slugs as they get a small electric shock when they make contact with the copper. Variations included copper coated pots stands. Can be expensive.
A variation on this is to use two thin pieces of copper wire lightly tacked to the top of edging boards on raised beds. Connect the individual wires to an old 12v car battery via a 1A fuse. If a big fat slugs tries to climb up the board it will be electrocuted when it touches both wires. Such a low voltage is harmless to birds, mammals and humans.
Some people have found that used coffee grounds are a good deterrent. Evidently slugs do not like the caffeine so do not use decaf! Some branches of national coffee shop chains are only too willing to giva away used grounds at the end of the day.
A tea made for the herb Wormwood is also said to be effective as is a mulch of the herb.
Human hair has been known to work. Collect from the hairdressers when you get your hair cut and sprinkle around vulnerable plants.
Others include; sharp ashes, soot, chopped gorse, pine needles, lime but be careful as this will affect the pH of your soil.
There is also a biodynamic deterrent. From Bio-dynamic gardening”, John Soper, 1983, p.100 “Some people have had good results […] letting the bodies rot in water until they are very decomposed and then sprinkling this brew several times , when the moon is in the Crab, over the worst infected places (M. Thun)”
Conventional slug pellets kill anything that eats those including dogs and cats and are should NOT be used in the organic garden. They are also implicated in killing large numbers of birds after they had eaten the dead or dying slugs.
There have been reports of the active agent in conventional slug pellets, metaldehyde, being found in drinking water. The widespread use of slug pellets on agricultural land has caused pollution of ground water which has found its way into drinking water. Water companies are complaining that it costs them a lot to remove the contamination so there is a chance that the widespread use of slug pellets will be severely restricted in the coming year.
A relatively new slug pellet based on iron phosphate, trade name Feramol, is approved for organic use. Try other methods first, do not rely on pellets, they are a last resort.
The other non-chemical, non-poisonous, treatment is nematodes which are microscopic worms that feed on slugs. They need to be applied every 6 weeks for total protection which can be expensive if you have a large garden. One of the best
ways to use nematodes is to treat seed beds at the time of sowing to protect newly emerging seedlings.
Ordinary oat bran is poisonous to slugs. Not sure why but when they eat it they die. Sprinkle round vulnerable plants, replace after rain.
This is still the easiest and low tech way to control slugs as all you need is a torch, a bucket and pair of gloves.
Trap them first using layers of damp newspaper under boards. Inspect daily and remove as you want.
Do not ne tempted to just throw them over the neighbour’s wall, slugs can find their way back!
A slight variation is the use of beer traps. You can buy custom made plastic pots or use old food containers. Place the lip of the container above soil level to avoid trapping ground beetles. You do not need to waste beer, there are several recipes around and this one is said to work well.
1 cup water
1 teaspoon sugar
1 teaspoon flour
1/2 teaspoon dried yeast
Hedgehogs are well known for feasting on slugs and can be encouraged in the garden by providing a nest box. It is then crucial that you should not use any poison controls.
Chickens and ducks also do a good job at keeping number down. If they could be trained to leave the veg alone they would be perfect.
Thrushes like snails and you might find empty shells by a stone or other suitable anvil they use for breaking them open. Although in severe decline numbers have rallied a little in some parts of the country.
A little know predator of slugs is the black ground beetle that you often find scurrying for cover when disturbed. If you use beer traps then make sure the lip of the trap is above soil level so that the beetles do not fall in.
Selection of varieties
One often overlooked way of reducing damage is to use varieties with known slug resistance. This is particularly important with root crops like potatoes and carrots e.g. the blight resistant Sarpo potato also has quite good resistance the slug damage of the tubers.