GARDENING / Slugging it out in earnest: The slimy pests have met their Waterloo, in a small slab of clay. Michael Leapman sows nemesis by nematode on his allotment

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The Independent Culture
A WET spring and a warm summer are usually good news for vegetable gardeners, and it has been a prolific year so far on my south London allotment. Almost the only thing I and my neighbours can find to complain about, apart from the odd shed break-in, is the time we have to spend directing the hose on to our plots. The bonus is that the ground is so baked that we have a fine excuse to lay off any digging for a few weeks.

But before I get down to boasting about my triumph with the red broad beans (and I shall, never fear), let me tackle the gruesome bit. Attentive readers will recall that last year I went down to Bath to look at experiments in breeding a predator, called a nematode, that would take care in its own way of that most prevalent of garden pests, the slug. This spring the nematodes came on to the market under the coy brand name 'Natures Friends'. They are marketed by Zeneca Garden Care, who invited me to test them.

It was neither a glamorous nor a simple assignment. The packet, which arrived by post, contained an alleged six million nematodes (I did not count) in a slab of clay. It had to be put in the fridge - an unappetising prospect - until conditions came right to use it.

The instructions ('Looking After Your Friends') were formidable. To make an effective test I was asked to measure the existing level of slugs both on the part of the allotment I planned to treat and on another patch, the control area that would remain untreated. To do that I had to put an inverted flowerpot on each patch for three days and, in the early morning, count the number of slugs that had gathered under it.

Since the allotment is three miles from where I live, I cannot just slip out there in my dressing- gown, and the feeble results of the test were probably due to my not getting there early enough. I found no slugs inside the pot on the area to be treated - although there were a few close to it - and just one on the control area.

The instructions warned against applying the nematodes when the soil was dry, or they would die before they had time to invade the slugs' bodies and carry out their deadly mission. The hot weather had by now set in and the pack was still lurking in the fridge, fast approaching its use-by date. Luckily, a heavy thunderstorm gave me a window of opportunity.

I diluted the nematode-filled clay as instructed and watered the microscopic bugs over the designated 20 square metres. Then I waited the recommended two weeks for the first test. There had been little rain since the storm and I wondered whether my spasmodic watering was enough to keep the little creatures alive. So it was with trepidation that, a few days ago, I lifted the two flowerpots which I had left in place to monitor progress.

The news is that the stuff does seem to work. On the untreated area, 14 slugs had congregated under the pot - perhaps escaping from the plague across the path. The pot on the treated area sheltered nothing but one plump snail. (Nematodes do not work against snails because they cannot penetrate the shells.) Although the leaflet says that the slugs die under the soil, there were in fact several dead or very ill ones on the surface of the treated area. After the slug dies, the bacteria from the nematodes swarm over its body and, with nothing left to consume, they go out and look for more slugs.

The package says that control lasts only six weeks. By then, presumably, there are not enough slugs left to sustain the nematodes. Given that one pack costing pounds 12.99 controls only 20 square metres, and that my allotment measures 100 square metres, it would be an expensive method to sustain.

So what summer feasts are the deceased pests missing? When we think of slugs we think of lettuce, and this year's crop has been ample enough to keep pests and humans well fed. I think the reason I, like everyone else, sow too much lettuce every year is because it is one of the first crops to go in. We sow it in the barren days of winter, when over-abundance is the last thing we can envisage.

My log informs me that I sowed two varieties of lettuce in a heated propagator on 20 February. They were Corsair, a new cos variety from Thompson and Morgan, and Lumina, from Unwins, with frizzy red-tipped leaves. Not content with that, I picked up a packet of seed of another red variety, Dapple, when I was in the United States in March.

In mid-June the first pretty leaves of the Lumina were ready for eating, followed a week or so later by the crisp, yellow-hearted Corsair. Dapple - a lovely deep red - was only a week behind, no doubt stimulated by being sown in mild south London rather than the chilly north-east of America.

I enjoy buying vegetable seed from overseas: it adds a faintly exotic aura to what can, let's face it, often seem a humdrum pastime. Sometimes the alien veg do well and sometimes, unsuited to local conditions, they fail. I was especially interested to see how I would fare with a few packets I brought back from Australia last year. Would they be fatally baffled by the arrival of summer in the middle of their winter?

Apparently not. For some years I have not grown kohlrabi - that round, turnip-style vegetable with the nutty taste - because I have never had much success with it, although as a member of the cabbage family it ought to be straightforward enough. I bought some seed in Australia of a variety called Early Purple and, sown in April, it has done exceptionally well, developing handsome, shiny roots with a delicate flavour.

I also bought an Australian packet of seed described simply as 'mixed squash'. This was a bit of a pig in a poke and success has been variable. A couple of the plants turned out to be yellow courgettes, and these soon keeled over with the complaint I have always diagnosed as cucumber mosaic virus - the leaves turn yellow and the stems separate from the roots.

When I discussed it with Pippa Greenwood after watching a recent recording of Gardeners' Question Time she said it was probably not mosaic virus spread by aphids, but something in the soil, because I confessed to growing squashes and marrows on the same ground most years - not good practice. However, other things in the same patch are doing well. Among the mixed squash is a plant that produces intriguing small fruit that look like scalloped flying saucers. On the same bit of ground a conventional courgette, Tarmino from Unwins, is racing ahead.

Most pleasing of all on the squash front is Thompson and Morgan's Cream of the Crop. This is already producing several distinctive pale green fruit of the type the Americans call acorn squash. The catalogue says they would taste like sweetcorn if I picked them now, but I prefer to wait until they mature and store them for baking in winter, when the need will be greater.

Another foreign experiment is a tomato that a friend brought back from holiday in the Canary Islands. I am not growing this on the allotment but at the back of my house, on warm south-facing steps, where it might get something like the temperature it is used to. It is not going to produce a heavy yield but those fruit that have appeared are large and growing larger, and I have high hopes for them in a few weeks.

My best tomato this year is Sungold, a small, prolific F1 hybrid from Thompson and Morgan that ripens to orange instead of red. I picked the first of them in mid-July and it is the sweetest tomato I have ever grown, although the skin is too thick for perfection.

Whenever I try sweetcorn I am disappointed. This year I followed the advice of another Gardeners' Question Time guru, Bob Flowerdew, and sowed them indoors in seed compost packed into the hollow centre of toilet rolls. The idea is that you can transfer the whole thing into the ground when the weather warms, avoiding disturbance to the roots. The cardboard eventually disintegrates.

Only five germinated from the dozen I sowed, and one of those failed to survive because the cardboard disintegrated before planting out. The cardboard also spawned a nasty green mould, so maybe I should change my brand of toilet roll. And after all that, the four survivors are not nearly as advanced as my neighbours', which are producing spikes of blossom already.

Finally, and well worth waiting for, the red broad beans. They are Red Epicure from Unwins, and it is the beans themselves, not the pods, that are red. They keep their colour after steaming and have more body than the conventional ones. Dinner guests are entranced, at least until I start my disgusting stories about slugs.

Zeneca Garden Care, Fernhurst, Haslemere, Surrey GU27 3JE (0428 645454 or 0892 784040).

Thompson and Morgan, Poplar Lane, Ipswich, Suffolk 1P8 3BU (0473 688588 or 0473 688821). Unwin Seeds Ltd, Histon, Cambridge CB4 4ZZ (0945 588522).

(Photograph omitted)