Organic allotments: waging war on pests

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?