Slugs : Gardeners' Enemy #1
Friday, April 04, 2008 by Jeremy Dore  - Categories: organic gardening
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 If there’s one garden pest that gardeners hate more than any other it’s slugs. After weeks of carefully raising small plants from seed, checking their moisture levels and carefully hardening them off outside, slugs can wreck it all. You take your prize seedlings, spend a hard day’s work planting them out and wake up the next morning to find them gone: often just the little stumps of stems and a slimy trail pointing the finger at the culprit. So what can be done?
In years gone by there was one standard answer: slug pellets. Spread a few around your crops and you wouldn’t have to worry about losing your plants. But slug pellets are poisons that cause considerable distress for pets, wildlife, birds and beetles. They usually contain metaldehyde (a pesticide) or methiocarb (an insecticide), neither of which are in keeping with organic principles.
So what solutions are open to the organic gardener? There are five main methods:
- Use Barriers: a ‘moat’ of gritty substances around your crops, copper rings (which produce a slight electric shock to the slugs) or plastic barriers (commercial or made from yoghurt pots) are all options. I’ve tried all of them but with mixed success – the slugs I get in my greenhouse seem to get past most of them!
- Drown Them: Slugs love beer, milk and most sugary/yeasty liquids and are attracted by the smell. So, saucers of beer sunk into the ground will attract them in and drown them – a relatively nice way to go perhaps? The resulting ‘drowned slug soup’ does need to be disposed of regularly though!
- Picking Them Off By Hand: Slugs come out at night, so a regular torch-lit trip to the vegetable plot at dusk can often reveal them ready for picking up and disposing of – or placing in a sealed container until the morning when they can be killed or fed to birds/chickens.
- Birds and Frogs: Birds may cause problems when it comes to ripe fruit and can scratch up young seedlings while searching for worms but they are great at finding slugs and snails. Frogs, too, can roam right through a garden reducing slug numbers if given a good pond environment to live in. The problems are areas where they can’t easily get to: a closed greenhouse, or brick and stony areas where the slugs can hide.
- Sacrificial seedlings and bigger plants: Slugs always go for tender seedlings in preference to established plants, so one option is to raise plants to a good healthy size in a slug-free area (such as a conservatory) before planting them out in their final positions. This can be coupled with providing some young foliage or seedlings for the slugs to eat in preference. The trouble is that this becomes a lot of work when you are talking about any reasonably sized vegetable plot.
- Biological control: An application of microscopic parasitic worms, called nematodes, is mixed with water and applied to the soil. The nematodes burrow into the slug and then breed inside it, stopping the slug from feeding as it swells up and eventually dies. It works well, even in wet weather but is not effective against snails. Personally, I think the long drawn-out death that the slug suffers (7-10 days) is not for me but it is widely used in organic agriculture.
I have tried all these methods apart from nematodes with varying success. Sometimes I gain the upper hand and through meticulously waging battle on the slugs I manage to raise early productive plants. Sometimes the slugs get through and, as happened last month, reduce a row of early peas to nothing in one night.
This year I am trying to win the battle by stealth: by concealing small plants and letting nature’s own predators do most of the clearing up for me. So nothing is going to be planted in the greenhouse bed until birds have had a good root through – everything is being raised high up or in large terracotta pots beside my house until I absolutely have to plant out. Then I’m going to go for a blended combination of techniques:
- Encouraging birds and frogs in the garden and opening up my greenhouse to them
- Waiting until plants are relatively big (a good 10cm/4 inches or more) before planting them out, then using yoghurt pots to protect them in particularly vulnerable areas and leaving some sacrificial leaves or seedlings for the slugs to eat in preference to my plants
- Copper tape around the terracotta pots to stop slugs climbing them
- Drowning them in beer – the excellent ‘Slug-X’ trap works well in my greenhouse and can be set up a few days before planting out
- Using old slate, empty coconut shells and grapefruit skins to provide little moist havens that the slugs hide in at the end of the night. In the morning I can just pick them up and dispose of the slugs elsewhere.
- Some late-night slug hunts by torchlight
I’d love to hear your ideas on what works well, so do add them below as a comment...
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