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As hard as it might be to believe, some slugs are beneficial to your garden! They can play a major part in clearing up dead and decaying material in the garden and can assist in managing the soil by incorporating humus and helping to form soil crumbs.
For most gardeners, however, the slug is a pest that destroys seedlings and more mature plants alike and many a grower has gone to his prized vegetables in the morning only to find them in tatters after a night of feasting by the slimy creatures.
Few gardeners would want to willingly encourage slugs and will be looking for ways to get rid of them.
The principal enemy of the slug is a hot, dry atmosphere for they have a skin, which is covered with mucus or slime that cannot dry out, if they are to survive. Making sure that there are as few ‘hiding’ places as possible is a start to reducing their activity. Of course, this is limited action and any light shower or overhead watering of the plants, will create ideal conditions for them. We need to find other methods of controlling them.
There are natural predators of the slug and these include the frogs and toads, centipedes and black ground beetles and many varieties of birds. In countries where the hedgehog is indigenous, it too will eat a large number of slugs. It is good to encourage some of these predators though, of course, some of them bring their own brand of threat!
The initial preparation of the soil is most important in a slug control regime and a soil that has a fine surface with no lumps will be less attractive to slugs. Make sure that your soil is well drained and not too alkaline.
Regular cultivation and hoeing of the soil can also help as it disturbs the slugs and their eggs and exposes them to the drying conditions that are fatal to them. If the slug problem is especially severe, the work on the soil can be followed by an application of aluminium sulphate though use of this should be limited as, currently, there are concerns about the part that aluminium may play in Alzheimer’s disease.
It is important not to make too much nitrogen available to the plants as this will make them more susceptible to attack. You should, therefore, avoid the use of fresh manure and artificial fertilisers.
Mulches, too, can encourage slugs as they provide places to hide. Avoid mulching young plants and always apply mulch to a warm soil.
Total protection against slugs for young plants can be achieved by cutting the bottom half off a 2 litre plastic drinks bottle and putting the top half (minus the cap) over the plant. It can be removed when the plant is big enough to survive on its own. Be sure to check for slugs before putting the bottle cloche on as any slug trapped inside will have a feast on the plant.
One of the oldest methods of slug protection is the use of some kind of ‘barrier’ around the plant. This could be made up of crushed (dried) eggshells, sharp sand, lime or wood ash. One of the most effective I have used was plain old soot from a sweep of the chimney. Not so easy to find nowadays but it works well if you can get it.
Another old-fashioned method that works well is the trap and one of the best is the beer trap. In this method a small container has beer put into it and then the container is placed on the ground where you know the slugs to be. They will climb in and drown and can be removed every few days. Try to ensure that the lip of the container is at least 2 cm. (approximately 1”) above the ground as, otherwise, the beetles that eat slugs will also get in and die.
Finally, you can pick slugs by hand or find them and sprinkle salt on them. This has the effect of dehydrating them.
There are, of course, a number of patent chemical options available such as slug pellets and slug tape and the aluminium sulphate already referred to. Unfortunately, pellets can be dangerous to pets and, because of their blue colour – said to deter birds – they might look like attractive candies to small children. If the non-chemical methods work then use those as a first choice.
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