The gardener who has prepared the soil well will find that not only vegetables and herbs benefit from the good environment. Weeds will grow very well too. Some of the highest plant densities on earth can actually be found in organic gardens whose gardeners have a lax attitude towards weeds. Don't hesitate. There are very few reports on incidents where weeds have physically attacked gardeners, although I once had a nasty experience when a seed capsule of a weed ( Oxalis corniculata ) actually exploded and shot a bunch of seeds in my eye.

If you think that the situation seems hopeless when weeds grow back almost over night, remember that this is a passing problem. The weeding season begins two weeks after sowing and continues for about four weeks. Weeds will continue to grow, but now your plants are so big that little harm is done to them. The weeds will suffer from the competition instead.

Mammal pests are a problem in all gardens and the damage they do is not smaller in the vegetable garden. The only sensible way to keep them out is to build a fence. To keep deer out the fence must be at least 1.5 m tall.

Insects and other small pests benefit from monoculture and an environment low in variability. Pests often survive on a single plant whereas their enemies have much wider requirements. Everything you do to create variation in your garden will tilt the balance over in favour of predators and other pest enemies. Even some lush weed patches may serve you in your quest for mastery in your garden.

Variation in the garden will not solve all pest problems. The next line of defence is to create barriers to prevent access, and when that does not work or is impractical, to take direct measures to decrease pest numbers by handpicking or setting up traps.

Plants prone to attacks from flying insects are best protected by physical barriers. Sheets of non-woven polypropylene are perfect for warding of carrot root flies and to prevent butterflies from laying eggs on brassicas. It is a labour efficient way of protecting large beds at low cost. The material is very light weight and can simply be laid out on top of the plants secured to the ground with stones. The disadvantage of this material is that it isn't very durable. It will last for two seasons if you handle it very carefully. It may also be of benefit to other kinds of pests e.g. slugs that will be protected from some of their enemies. Large numbers of caterpillars are to be expected on brassicas. As long as they feed on the larger leaves picking the caterpillars is one way to get rid of them. Try to spot and remove eggs as well. The eggs are very small - less than two mm, but once you develop a search image for them they are easy to find. To make it easier the eggs of some species turn bright yellow before hatching. Often the eggs are found in masses of 50 eggs or more. Chase all white butterflies away from your garden.

Birds are not only predators. Many species will try to feed on your plants. Berries and fruit are at the greatest risk. Plastic nets are the obvious solution - cheap and easy to use. The disadvantage of nets is that birds can get entangled and even killed. Try to get nets that have been approved for bird safety.

Pests that crawl on the ground are often active at night when they are harder to spot. During daytime they will hide in cracks, ditches and under stones where they are unlikely to be encountered by the gardener. By providing excellent day shelters for these animals they can more easily be rounded up and killed. Boards, planks and other flat objects laid directly on moist soil are likely to attract many villains. The boards work better if they are in the shade. Make sure that they don't lie to flatly on the ground. There must be suitable spaces under them. Remember that not all animals that are found under these boards are pests. Most beetles and centipedes are predators. There are even predatory slugs, but unless you can tell which ones it's wise to remove all slugs and snails. Insect larvae, earwigs and millipedes are also in most cases better dead.

If you leave the boards for some time ants will often nest under them. Ants are mostly beneficial because they attack practically every pest that one can think of. The exception is aphids that ants tend like cattle. They even move aphids to previously uninfected plants. In return for help and protection the aphids produces secretions rich in sugars that the ants drink. If aphids are a major problem then one could consider to get rid of the ants. To eradicate ants without resorting to poisons is not possible, but frequent disturbances of the nest can often persuade them to nest somewhere else.

A better strategy is probably to forget about the ants and fight the aphids directly. Removal of affected soft tips of shoots is quite effective. Naturally you don't want to remove the top shoot of a plant unless the plant is fully-grown. Soft soap is a good option. Soap disrupts the surface tension of spray water. The aphids are entirely soaked in water and drown. Go out and collect some ladybirds. They are aphid specialists and will kill the aphids for you in almost no time at all. The lady bird larvae are equally efficient. They don't look like adult lady birds, and might be taken for pests. Whatever you do don't kill them. The larvae of many species are up to 10 cm long and blackish blue with some orange spots. They climb around with great agility on the leaves and stems of aphid infested plants. The larva in the picture has attached itself to a leaf and begun the pupation process.

Crucifers like cabbage and radish are often attacked by flea beetles. This 3-mm beetle jumps from the plants when the gardener approaches. They will not like you if you spread something dusty on the plants. wood ashes are good. Another method that I have only red about is to use a small portable vacuum cleaner. I can believe that it actually works. To sow brassicas in a cold frame is a less spectacular way to have some control over the situation. When flea beetles are frightened they have a tendency to climb up on the sides of the frame where they can easily be crushed. Armed with a little patience one can kill almost all of them. It is much harder to fight them on the crumbly soil surface where they are practically invisible.

Wireworms are the golden brown larvae of click beetles. The larvae live in the soil for up to five years before they pupate. Click beetle females lay eggs preferably on grass covered ground. Cleared soil is unattractive and wireworms are a problem mainly in newly cleared soil. After four to five years you can forget about them, but until then they can do some serious damage. In my garden they have primarily damaged potatoes and seedlings of beans, lettuce, onions and marigolds. The larvae have the regrettable habit of gnawing seedlings off just below the soil surface. The first favourite seems to be lettuce. Gardeners can use that to their advantage. If lettuce is sown together with beans the wireworms will eat the lettuce but leave the beans almost undamaged. It is not certain that all varieties are good but they love Great Lakes. When a lettuce seedling dies the culprit can often be found if one scratches the soil next to it.

The art of getting rid of slugs and snails is a very common subject of discussion whenever gardeners meet. Everyone has his or her favourite technique. Most of them probably do not work at all, hence the eagerness to learn from others. Slugs and snails are rather stationary. If I kill slugs in one corner of my 50 square meter garden I can see a reduction in slug damage in that corner for a week or more. The least complicated method is often the best. Step on all slugs and snails as you find them. If that is too greasy for you, chop the slugs in two and crush all snails with the hoe, or pick and release them a hundred meters from the plot (or in the gardens of your enemies where they can actually do some good). The key to success is to know when to be in the garden and where to look. The animals are most likely to be encountered in early mornings, late evenings, after a rain or whenever the ground is wet or moist. In sunny but not too dry weather they will be going about their business in the shade under dense canopies. Examine all plants with dense foliage that touch the soil. They may also be found in dense bushes e.g. Hyssop, and under your boards of course. In really hot and dry weather they will retreat to deep cracks in the soil, to ditches and piles of stone. There they are often very hard to find. Small snails and slugs can be difficult to spot. They often blend in very nicely with their environment. Try this! Put up some Sheets of white non-woven polypropylene vertically. Obviously you will need some sticks, a piece of string or something like that to achieve this goal. Make sure that the edges of the sheets are in close contact with the soil. Give the sheets a good spray of water in the evening. Return after a couple of hours. If it is dark - bring a flashlight. Try to figure out where the slugs and snails are likely to hide and erect the barrier between this place and the affected plants. Some slugs actually burrow into the soil. To catch these put the trap in the middle of your beds. Sometimes it works, sometimes it doesn't.

Carrots are doomed to be attacked by carrot root flies. I frequently lose around 20 percent of the harvest. Females deposit their eggs on the soil next to carrot plants and the larvae burrow into the roots. The best prevention is to deny access to females. Females tend to fly just above the soil surface when laying eggs and a 60 cm tall barrier around the carrot beds reduces the problem significantly. Females use the smell of carrots to home in on their target. Carrots smell more when you touch them or work the soil around them. Females are active when the weather is warm and dry. Try to weed and harvest carrots early in the morning, in the evening or on a cold and rainy day when females are not flying.

Two legged pests are the worst that one can have in the garden. Not only do they steal the harvest - just for fun they destroy the result of all that work that you put in. Fortunately they are fairly easy to get rid of. Use a lasso to catch them. Lower them down completely into a barrel of wallpaper paste mixed with rotting slugs. Roll them thoroughly in fresh farmyard manure. After this they are most unlikely to come back - ever. I have used nailboards too, but gave this method up after having stepped on them a couple of times myself. It's easier than one might expect to forget where the boards are. I have also been thinking about combining a beehive and tripwires. When the pest trips on the wire a support is snatched away and the hive falls to the ground. Then the bees will come out and start looking for the unfortunate pest who is responsible for their misery. Forgetful as I am I have not dared to put these plans into action.

Think about what you bring into your garden. To buy vegetable seedlings is risky. The plants and the soil that they come in are sometimes infected. Don't use tools that have been used in other gardens without cleaning them thoroughly. Don't bring in garden compost or soil from other gardens, especially not from vegetable gardens.

Stressed plants are more susceptible. Plants that suffer from nutrient deficiencies, drought or other types of stress are more likely to succumb to disease than those are that can grow unchecked.

Excessive fertilisation, especially with nitrogen, reduces resistance to disease (and stress) in many plants.

Most diseases are specific to certain plants or groups of related plants. You can make it more difficult for these diseases to build up by moving plants around from year to year. This practice is called crop rotation. There are a number of good reasons for crop rotation.

• The first idea behind crop rotation is to starve out soil-borne diseases and harmful insects present in the soil by depriving them their host plants for as many years as possible before the plants return to the same spot again. Especially brassicas and potatoes, but also other plants, can be severely affected by soil-borne disease. The alliums (onions etc.) are susceptible to white rot. Once present in the soil this disease will remain for many years. Crop rotation makes it harder for the fungus that causes the disease to build up in the soil.
• Plants have different needs for nutrients. Carrots do better in soil that has not been recently manured, while cucumbers cannot have too much manure and compost. Rotation makes it possible to give every crop what it needs and still add plenty of organic matter to every corner of the vegetable garden in a few years time. Some plants also have special needs for specific nutrients. Rotation reduces the risk that these nutrients will be depleted in any part of the garden.
• Finally some vegetables are particularly effective at suppressing weeds. A crop of potatoes may leave the soil nearly weed free for the next crop. Crop rotation allows the whole garden to benefit from these weed killers.

Rotation is usually recommended for vegetables, but should be practised with perennial plants like raspberries and chives as well. Strawberry plants last for three to four years. When you replace them, find a new spot.

For crop rotation to be effective against pests and diseases that are specific to groups of plants it is essential to know the groups and make sure that plants from the same group do not follow each other in the rotation.

These are the most important groups: