Choose Pest-Resistant Cultivars
Good soil conditions and a liberal supply of nutrients, water, light and air are important for healthy plant growth. The choice of varieties also has a crucial influence on whether or not your vegetables will be attacked by pests. Summer varieties planted outside in spring always do badly and have little resistance to attack. Likewise, outdoor varieties that are kept under glass often fall prey to pests and diseases. Always choose appropriate varieties for your situation and use cultivars that are resistant to fungal, bacterial or viral infections as well as to common garden pests.
Plants to Help One Another
Companion planting makes the most of the beneficial effects that plants can have on each other and on pests. Aromatic compounds in roots, leaves and flowers or secretions from parts of some plants can act as effective deterrents to many common pests. Growing carrots with leeks, garlic or onions is a tried and tested combination, with the companions protecting each other in turn against carrot fly and onion fly.
When planted between strawberries and vegetables, onions and garlic also help to protect against fungal infections. Strong-smelling winter savory protects dwarf beans against blackfly, whereas nasturtiums help to protect tomatoes and fruit trees from greenfly and the woolly apple aphid. When planted among vegetables, secretions from the roots of pot marigolds (Calendula officinalis) and French marigolds (Tagetes patula) help to deter eelworms.
Planting celery between cabbage plants drives away cabbage white butterflies, so that they look elsewhere for a place to lay their eggs. And the aromatic leaves of sage also deter cabbage white butterfly as well as being offputting to snails and ants. As well as protecting against pests, companion planting results in fewer weeds as deep-rooting plants grow alongside shallow-rooting plants, compact plants with broad leaves alongside thin-leafed plants. This means there is less room for weeds to take hold. Use netting, horticultural fleece and collars to keep vegetable fly, leek moth and cabbage fly away from your vegetable patch.
Spraying with an infusion of horsetail (Equisetum arvense) helps to prevent fungal infections. Just boil up two dessert spoons of the dried weed in two litres of water, leave to infuse for 15 minutes, cool, then strain. Every two or three weeks, on a sunny morning, spray the infusion over the plant and the soil.If you grow vegetables in the same position year after year, certain pests and diseases will be quick to establish themselves, lying dormant in the soil between growing seasons. You can prevent this by rotating crops in the vegetable patch.