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Slugs & Snails

October 13th, 2013 | Posted by TOGSJames in Key Topics
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How do I deal with slugs and snails in the organic garden?

Certainly not by sprinkling vast quantities of those traditional blue metaldehyde and methiocarb pellets available cheaply at all garden centres and DIY stores! These chemicals are dangerous to wildlife predators of slugs and snails such as hedgehogs and thrushes, slowworms, frogs and toads, the very creatures that you want to encourage in your organic garden. Metaldehyde is even dangerous to pets such as cats and dogs. Just try googling ‘metaldehyde poisoning’ and see how many veterinary sites come up. In fact, British farmers are irresponsibly using such quantities of metaldehyde pellets on their field crops that our drinking water is in danger of contamination. Log on to www.pelletwise.co.uk.

The Great Black Slug (Arion ater)

The Great Black Slug (Arion ater)

The Garden Snail (Helix aspersa)

The Garden Snail (Helix aspersa)

OK, so if I don’t use poisonous pellets, what alternatives are there?
Alternatives for killing slugs and snails, or alternative ways of protecting your crops and plants against them?

Both!
Alright, first, we must think of protection, protection, protection. It’s no good sowing veg seed, or putting young veg plants in the soil and simply leaving them unprotected, to the mercy of any passing pest!

So cover rows of seed and seedlings with horticultural fleece and keep them covered for the first few weeks, making sure that no slugs or snails have got in under the fleece. In his book, Successful Organic Gardening, Geoff Hamilton advises ‘surrounding young seedlings and shoots of young herbaceous plants with plastic bottles which have been cut off at the bottom’ and this certainly has been found to be effective in our experience, simply because of the physical impossibility of the slugs or snails getting inside the bottles.

We have also done experiments with sticky copper tape round pots of hostas, and round the edges of wooden raised beds. It really works, but is quite expensive to buy. We experimented with Vaseline round the pots instead as a cheaper option, but it had no deterrent effect whatsoever.

In wet weather generally, when slugs and snails abound, all the top organic gardeners agree that there is no substitute for inspecting plants daily, particularly after rain, clearing out corners of raised beds where slugs and snails hide during the day, inspecting nearby stone or brick walls and removing ivy, and turning over pots and trays to discover the slugs and snails lurking underneath.

Alison Mundie, Trials Officer RHS Harlow Carr Gardening says, ‘ Clear away protential hiding places, such as piles of leaves in shady corners – remove them to a compost heap or dig them back into the soil. Any other rotting vegetation needs removing as it will attract them and provide perfect breeding ground.’

Geoff Hamilton’s suggestion of ‘venturing out at night when the slugs are feeding and simply picking them up and dropping them into a jar of paraffin’ is not acceptable nowadays. Best then to follow Alison Mundie’s suggestion to ‘Arm yourself with a torch, a bucket of salted water and gloves and physically remove the pests. Pick the creatures off and drop them into the salty water, which is lethal to them. Once dead, drain the water and empty them on to the compost heap. Continue the nightly patrols regularly, especially after rain.’

Going out at night with a torch and collecting slugs and snails will give you some idea of the odds you face at any particular time. No amount of poisonous bait can deal with such creatures without decimating the hedgehogs and thrushes that prey upon them, not to mention the effect that eating poisonous bait can have on pets such as dogs and cats.

Are there any safe pellets I can use?
Yes, there are two new and distinct types of pellet available, the bait type and the granule type. The bait type consists of tiny blue pellets containing a bait or attractant mixed with ferric phosphate, which kills the slugs and snails by drying them out. The instructions are to scatter them thinly over the bed in a random pattern, and we have had some success with them, particularly with Growing Success Advanced Slug Killer rain-fast pellets.

The second type comes in granule form and looks like pea gravel, and has to be put in a circle round the plants to protect them. It comes in cardboard boxes with the name Slug Stop or Slug Stoppa granules. The theory is that the granules will suck the slime and dehydrate any slug or snail that attempts to crawl over them. We have tried this method, and it works, but only for smaller slugs and snails, and only if the granules form a solid undisturbed circle of protection.

Where can I buy these safer pellets and granules?
You can buy them in most garden centres, such as Fermoys and Otter Nurseries locally, or DIY stores, such as B&Q and Wilkinsons. They are more expensive than the traditional poisonous metaldehyde pellets, but you do have the satisfaction of knowing that you are saving the lives of thrushes, blackbirds and other wildlife. You can order Fito Slug Stoppa granules for £8.45 a box online from the Organic Gardening Catalogue, whilst Growing Success Advanced Slug Killer pellets cost £6.95 from the Organic Gardening Catalogue or Harrod Horticultural. The cheapest place to buy granules and pellets locally is Trago Mills, near Newton Abbot.

What are nematodes and how do they kill slugs?
Nematodes are microscopic eelworms (Phasmarhabditis hermaphrodita) used for the biological control of slugs in the soil, and so are ideal for potatoes. They are used at RHS Harlow Carr, and at Highgrove for plants under glass or outdoors. The eelworms seek out the slugs in the soil and kill them by burrowing into them and introducing a bacterial infection when reproducing inside the slugs. You buy the nematodes in packs, mix them with water and apply to the soil with a watering can or sprayer, which will give you protection for up to six weeks. The manufacturer admits that the product ‘does not control snails, and kills mainly young and small slugs in the soil, rather than big slugs on the surface for which additional controls may be needed.’

How do I buy nematodes?
Nematodes are sold as ‘Nemaslug Slug Killer’. You can order them online, from the Organic Gardening Catalogue (small pack for £11.60), or Harrod Horticultural (small pack for £9.95).
See our Useful Links page.

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