Gardening: Just slug it to them

Go outdoors after dark and you'll probably find hundreds of slugs munching your plants. But pellets aren't the answer, says Sarah Raven. Biological warfare is
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The Independent Culture
WHEN I lived in London, if I went down to the kitchen in the middle of the night, I was always greeted by them: three or four huge slugs, two or three inches long and an inch wide, the colour of terracotta with splashes of beige, sitting on the saucer of cat food and munching away. Aren't slugs vegetarians? Don't they want to eat only lovely lush green leaves? No, they prefer to squeeze in under the French windows and eat meat. And even if I didn't see them, they left their cat-food-stained slime trails as a reminder.

I was a doctor then and was being taught by a biologist who loved slugs. Apparently mine were quite rare. There are four main garden slugs: the grey field slug (Deroceras reticulatum); the garden slug (Arion hortensis), which is shiny black with a yellow belly; the keeled slug (Milax budapestensis), which is black with a thin orange line down the centre of its back; and the black slug (Arion ater), which is usually black but can be red-brown if you're lucky. This was mine, famous for being the biggest of the lot.

I hated them. I hate all slugs. I hate their mucous sliminess and their fecal looks. They are leech-like and primitive and I despair when they eat through precious seedlings in the garden or greenhouse. Zinnias are one of my favourite plants and slugs love them. A slug will take out a full metre of nascent plants in one night. If you sow more, the next lot of plants are at least a month behind the others and what guarantees are there that these will be safe? Slugs devour your lines of lettuce, your prize emerging delphinium spikes; they scar hosta foliage and graze their way through main crop potatoes as they grow in the ground. They are a pest. How can you control them?

Snails are visible so you can tread on them, or collect them for taking elsewhere. I have to admit I used to transport carrier bags of snails to the local park in London and feed them to the ducks. We have ducks on the pond in our garden now and don't often see a snail. But it's not as easy with slugs. When they first hatch, many young slugs are only a centimetre long, but despite their size they can do a lot of damage. As small as this, they are hard to see and, in any case, disgusting to pick up.

Lots of people use slug pellets. These contain either an agent which paralyses the slugs (metaldehyde) or a poison (methiocarb). Metaldehyde stops the slugs in their tracks. They can't move to shelter and so dry out and die, as you'll see if you put these pellets down. There will be a collection of slugs in an area all around the pellet which are still alive, but can't move. These pellets are nasty for slugs, but nasty for lots of other things, too. They will kill fish if any get into your pond and they are poisonous to humans, pets and birds. Thrushes and hedgehogs like slugs. If they feast on a static swarm of slugs around a pellet, they will be dead within a few hours. Don't use them.

A friendlier alternative is to use a slug trap and a liberal scattering of grit around your most prized plants. A good inch or two of grit in a two inch-wide line down each side of your lettuces will discourage slugs. The sand in the grit will make the area dry, which they don't like. For a slug trap, just sink a jam jar so that the top is flush with the soil level and fill it with beer. The slugs, attracted by the smell, go in for a swim. They can't crawl out because they're drunk and so they drown. I used to chuck any slugs I found in the greenhouse into the water butt outside, not realising that they can survive in water until they crawl out - you must use alcohol.

Traps work well if you don't have too many slugs, but you'd have to have a garden littered with sunken jam jars if you had an infestation in a cool, wet year. Most slugs live in the soil in the day, coming out at night to feed. To get an idea of how many you have, go out after dark with a torch and look at your lettuces or a clump of hostas. It's then that you'll see the true, horrifying picture. Expect an average of 200 slugs per square metre.

I vote for biological control and a tidy garden to get on top of slugs in these numbers. They love hanging about in straw, damp leaves and a thick covering of weeds like chickweed or fat hen, which provide a moist environment for them to thrive. Get rid of as many of these hiding places as you can and you are halfway there. Combine this with Nemaslug, a powder you mix with water that contains millions of tiny nematodes (microscopic worms which exist naturally in soil). These are fatal to slugs. The nematode carries with it a bacteria which is the killer. It burrows into the mantle of the slug, at the back of its neck, and poisons it. The slug stops feeding immediately and will die underground within a day or two. My husband says that gardening is nothing but applied violence. I haven't told him exactly how my rather sweet-sounding "biological control" works. It's bacterial massacre.

Nemaslug will have a killing effect for six weeks, above and below ground, and is lethal only to slugs. If you apply it in April, the six weeks will get you through the most vulnerable stage of growth.

Nemaslug has a couple of disadvantages. It is only acti-vated above 5C/40F, so is no use before the middle of April in this country. Slugs are not very active in the garden in the winter and early spring. Many lay eggs and die in the autumn and the eggs will not hatch until the spring. This means that the few early emerging plants in the garden should be safe, but slugs can be a problem in a cold but frost-free greenhouse full of promising half-hardy annual seedlings in March and early April. You will have to rely on other means of slug control to protect these.

Nemaslug is perishable, too, which is why you will not find it in your garden centre. Each packet has a shelf life of two weeks if you keep it in the fridge. This apart, it is Nemaslug and not the slug pellet that we should all be using to execute our little slimebags. Death to the invader.

You can order Nemaslug from Green Gardener (tel/fax 01603 715 096). A standard pack of Nemaslug costs pounds 11.95 inc p&p. This will treat 40 square metres/50 square yards

This week

The early flowering tulips have come into their own in the last week. The Single Earlies are in full bloom in my garden. T `Generaal de Wet', an orange tulip in this group, has a delicious freesia-like scent and there is a flamboyant bi-colour, `Mickey Mouse', with buttercup yellow flowers and stripes of scarlet, in flower too. Single Earlies are followed by the Darwin Hybrids, Triumphs, Lily-flowered, Viridifloras and last of all the Parrot tulips. Whenever you see a tulip you like in someone else's garden, make the effort to ask what it is and write the name down so that you can order them for yourself for next year