Anna Pavord's A to Z of pests and problems: E is for eyesores, edibles, envy and earwigs

Our green-fingered correspondent Anna Pavord continues her A-Z of the pleasures and pitfalls of gardening.

Earwigs

These generally get a bad press, which is not entirely fair. They have an unfortunate liking for the flowers of clematis and dahlia. But they are also good predators and can deal effectively with several far worse pests: small caterpillars, aphids and the eggs of codling moths.

Earwigs are most active between May and October. They are night feeders, resting by day in cool, dark hidey-holes. The traditional trap is a flowerpot stuffed with straw and stuck upside down on a pole near the war zone. The idea is to empty the flowerpot and its attendant earwigs somewhere far from the scene of the crime.

Other similar traps are equally effective. You can make rolls of corrugated cardboard or sacking to fix on sticks. Hollow broad bean stalks stuck in the ground also attract earwigs. If you suddenly feel like squashing them, think what exemplary mothers they are. Unusually among insects, they show some interest in the eggs they have laid. If their maternal qualities leave you cold, remember what they are doing to the aphids.

Edible

We keep hearing about the 'upsurge' in growing food, but actually it's a myth in the making. Among gardeners, the love for and interest in growing food has never gone away. Even the first staggeringly tedious edition of the RHS Vegetable Garden Displayed (1941), sold 71,000 copies. It sold many more than that in subsequent editions. Joy Larkcom (the most influential person of all in this field) published her first piece in 1974 and a series of seminal books on edible crops in the Eighties. The New Kitchen Garden, which If wrote in 1996, sold more than 160,000 copies. And remember that though a lot has been written about the rush for allotments, rather less notice has been taken of the numbers who don't even stay the course of the first year on their plot.

Eelworm

Unlike the earwig, this is a baddie with no redeeming features. Microscopic stem and bulb eelworm infects narcissus, invading the tissue of the bulb and multiplying so rapidly that a million can exist in a single bulb. You will know if you have got it as flowers collapse completely. Burn infected stock and do not replant bulbs in the same place for a while.

Potato eelworm can also be a big problem. These are soil-borne pests that hatch out from eggs protected by a tough brown cyst. The young eelworms home in on the roots of potato plants. In the worst instances the whole plant dies. Crop rotation is the best defence. Do not grow maincrop potatoes on the same patch more than once every five years. Some varieties of potato have partial resistance to eelworm. Look for 'Cara', 'Concorde', 'Jewel', 'Maris Piper', 'Morag', 'Penta' and 'Pentland Javelin'.

Envy

It's bound to happen at some stage in your gardening life. You are envious because the person on the next door allotment has evidently decided to give up on potatoes, while you are still struggling with blight and eelworm. At a different point on the continuum, you are envious because the person on the allotment beyond that has an excellent crop of potatoes in the year that you have decided to abandon them for ever.

Gardeners are always envious of other gardeners' soils. Ours is such a tiny country, with such a complicated underpinning, three or four different soil types can easily exist within the same parish. In America, they talk zones (climate zones that is) and have zone envy. Over here we talk chalk, clay, acid, alkaline. After a lifetime gardening on clay and getting the superior "Poor you!" from people on chalk, I now garden on the fabled greensand, which you are not supposed to get until you go to heaven. So now, on the soil front at least, I can watch envy build up in other gardeners' eyes, rather than feeling it welling up in my own.

It's permissible, understandable even, to envy the soil other gardeners have. And their south-facing slopes, their shelter from the wind. It's not possible to do much about these givens, if you've not got them. But what you should never envy is other people's expertise. You can get there yourself, if you try hard enough. You, too, can prune a vine to perfection. You, too, can raise flowers from seed. You, too, can pick a brimming bowlful of fresh peas. It just takes application.

Erwinia amylovora

This is more commonly known as fire blight and gets its name because affected trees and shrubs look as if they have been scorched and blackened by flames. It is most likely to affect pears and other members of the Rosaceae family, such as apple, cotoneaster, hawthorn, mountain ash, pyracantha, quince and whitebeam; it's more prevalent in southern counties than northern ones.

It is a bacterial disease which you are most likely to notice when a tree or shrub comes into flower. The blossom turns black and withers and the blackness bleeds back into the stem. Flattened areas like pock marks develop on the branches. When the bacterium that causes the disease reaches the trunk of the tree or shrub, it (the tree not the bacterium) dies. There is no known cure. Diseased wood must be cut out and burnt to prevent this virulent disease from spreading. Disinfect secateurs and pruning saws afterwards.

Eyesore

One gardener's eyesore is another gardener's pride and joy. So before you complain about your neighbour's new shed, ask yourself what your neighbour might be thinking about your polystyrene statue of Venus emerging from her bath. Some eyesores – your own – can be disguised by clever planting. Cover shed walls with galvanised pig fence or chicken wire and then throw climbers at them. Stay away from bullies such as Russian vine (Fallopia baldschuanica) which will send out tendrils strong enough to tear the planks of the shed apart.

Other people's eyesores are difficult to block out from every angle. Choose the viewpoint from which you are most likely to catch the horror and plan some feature in your own garden – a tall wigwam, a fast-growing shrub or tree (but not Leyland cypress which will quickly become an eyesore itself), an arch, a totem pole to swathe with honeysuckle – which will blot it out.