Gardener's World magazine's Jane Moore draws up battle plans to defeat the ever-present, hungry hordes and tries to stay one step ahead of the enemy

Reproduced from August 07 issue of Gardeners' World magazine. This month's issue on sale now. Subscribe now by direct debit and save 25 per cent.

The fruitfulness of the plot in August is a wonderful thing. But there's a war going on out there between allotmenteers and bugs - aphids, slugs and snails, things that fly, crawl and slime, all munching away furiously at our lovingly cared-for crops.

It's not easy being organic, but I work hard to keep on the path of righteousness and always find it so satisfying that we manage to grow crops without resorting to chemicals. I'm sure they taste better, too. It's a constant battle against slugs and aphids. And although we always write off a proportion of our crops to the bugs, we have found that the strongest and healthiest plants do survive and produce plenty for us to eat. It's a bit of a balancing act really.

We always grow more than we need, and if we lose a few, so what? And, by being organic, we definitely have more good insects around, such as ladybirds, to eat up some of the baddies. Not to mention the birds and hedgehogs that happily call our allotment home.

Organic controls

Being organic is a labour of love. It's not simply about stopping spraying, although that's a good start. It's about minimising the chances of your plants being attacked in the first place. A healthy plant is a happy plant that grows strongly and can resist the onslaught of pests and diseases.

• To start with, you need good soil that has been well fertilised with plenty of organic matter in spring. Second, your plants need to get off to a good start, which means sowing fresh seed at the right time and in the right way, so germination is swift and early growth rapid. Carrots just won't germinate if it's too cold or if you sow them too deep - 2mm is perfect, which is barely below soil level. Slug and snail favourites, such as courgettes, are always best grown in pots until they're big enough to plant out, and you only need a couple of plants to feed a family.
• Tidiness is next to godliness on the plot, because a mass of weeds or long grass can hide an army of slugs and snails. That's one of the reasons why raised beds are so good. The edges are clearly defined and keeping the paths in between clean is easy. The beds at one end of our allotment are not edged and 10 times harder to manage than the edged ones, because the grass paths that surround the place spread into the crops as the season progresses and we can't keep it tidy.
• Finally, crop rotation is a must for organic gardening because it stops diseases building up in the soil and allows you to clean up areas, as well as making the most of nitrogen fixed in the soil by crops like beans. We try to follow beans with a fast-and-furious leafy crop such as salad leaves or cucurbits (gourds). And this year we're trying to clean up a bindweed-ridden corner by covering it with weed-proof membrane and planting courgettes through it. Hopefully, the courgettes will grow well and the bindweed will be weakened after months without light.

Disease-resistant varieties

Plant breeders and seed suppliers are always looking for varieties that show resistance to certain diseases that are common to particular plants. For example, maincrop potatoes often suffer from the fungal disease, blight. Many gardeners get around this by growing early and second-early varieties that are harvested before blight strikes, usually in August. Or you can grow one of the new wave of blight-resistant varieties, such as the Sarpo series. These did prove to be blight resistant when we tried them, but they didn't have the best flavour so we've dropped them in favour of riskier, but more flavoursome, varieties.

One disease-resistant variety I am keen on is parsnip 'Avonresister', which is tasty, a good grower and only gets the odd spot of canker. I have had whole crops infected with this unsightly fungal disease in the past, which is so disappointing, so now I stick to 'Avonresister'.

Organic chemicals

There is an increasing number of organic chemicals on the market, plus several that are allowed as organic by the Soil Association and Garden Organic (also known as the HDRA). Slug controls often work to some degree but, if it's a bad year, you'll need the full arsenal of traps as well. I've found that barrier gel deters slugs, but not as effectively as copper rings. Nematodes also work well but are short lived, and you do need to apply them when the soil is warm, usually in April, which can be a bit late for newly emerging seedlings.

If you have to resort to the hard stuff, then copper fungicides, such as Bordeaux mixture, are permitted to control blight, as are plant-based insecticides such as derris and pyrethrum and insecticidal soaps. But only use them if you're desperate, as they do kill friendly bugs too. I'm glad we've never needed them.

Deter pests with companion planting

We all benefit from good company, and plants are no different. The trick is to make sure that everything you plant has a specific function.

Although these planting companions are not foolproof by any means, they can certainly help your crops stay healthier and add more variety and diversity to the plot, which will improve its ecology and increase the number of potential predators.

• Brassicas can be protected to some degree from the attentions of cabbage white butterflies by planting French marigolds around them. The smell of the marigolds masks that of the cabbage family and they are also useful in deterring whitefly from tomatoes.
• Carrot fly can be put off the scent by planting rows of pungent plants such as onions or thyme, with the carrots in between.
• Some plants, such as garlic and chives, are good for repelling aphids and they taste great, too.
• Lots of plants, including California poppies, Eschscholzia californica, poached egg plants, Limnanthes douglasii, and pot marigolds, Calendula, attract beneficial predators such as hoverflies, and are worth dotting about in spaces that are too small for anything else.

Choose your anti-pest measures

Barriers
These can be simple and straightforward, such as a cut-off plastic bottle to keep a precious seedling safe from slugs or cool night temperatures. My favourite anti-slug barrier is probably the copper ring - it may look unlikely, but it works brilliantly. Last year, a ring around a young courgette plant protected it effectively and it grew more strongly than the others. And the French beans really blew us away. We put rings around a handful of plants at random and they all grew beautifully, while others were variously nibbled and munched, some to complete oblivion. I have heard that copper tape works well, too, around pots or even raised beds.

Screens
Carrot fly is a real nuisance, leaving carrots half-rotten and riddled with holes. The best organic way to protect crops is to put a 60cm-high screen right around the bed. Carrot fly tend to fly low to the ground looking for a sniff of carrot, so a barrier will keep them well above your crop. It's also best to keep the thinning of seedlings to a minimum and to tidy up any thinnings promptly, so carrot fly don't catch a whiff of bruised carrot, which definitely attracts them. You can make the screen from old net curtains, fleece or anything similar.

Traps
Slug traps are widely available and hugely popular among organic gardeners, because we like to think the slugs die happy and sozzled. They certainly are very drawn to beer - as indeed are many allotmenteers - and strategically placed slug traps do work, provided you empty them and replace the beer regularly. Other traps include codling moth traps for apple trees and humane rodent traps.

Netting
This is a must on the plot. We use netting to protect fruit bushes and strawberries from birds, and brassicas from pigeons (why do they find brassicas so tasty?). It's also handy for shading young plants and those prone to bolting, such as lettuces, in the hot sun.

Vibrating string
The idea is that the noise scares off birds, including pigeons, but it only works if you have a breezy plot, and then it makes a heck of a racket. When Ron next door first used it, the noisy thrumming almost scared Lizzy and me away until we realised what it was, noticed the lack of birds around Ron's plot and thought: 'We'd better get some of that!' Simple, cheap and effective.

Scarecrows
They're such fun to make and see around the plot, but do they actually work? I doubt it, but does it really matter?