Serious diseases are not common in the garden, especially if well cared for, and you probably won’t have to deal with anything more serious than an invasion of plant lice or a non-severe case of downy mildew or white sickness.
How to stay out of trouble
Usually, in the case of diseased plants, it is easier to eradicate and burn them than to try to save them using chemicals. Vegetables are not long lasting plants, so you can simply try planting them again. In this article you will find a list of the most common pests and diseases.
Remember that your vegetables don’t have to be affected just because they are on the list: with a little care and common sense, this won’t happen. The secret to success is to keep your plants healthy, so they won’t be attacked by pests or diseases.
If you do not sow directly, buy the plants from a trusted dealer and never transplant them if you think they might be sick, especially if they are brassicaceae. Always make sure they are in the best conditions to grow well: light, air (but not strong wind), water and nutrients. Don’t let drought slow plant growth: mulch the soil and irrigate regularly so that the plants have enough water and grow vigorously.
Another important factor is the balance of the garden. For many harmful organisms there are specific predators: for example ladybugs, chrysops and hoverflies destroy large quantities of aphids, while carabid beetles eat red snails and underground larvae. If you have flowerbeds with many different plants it is likely that a large number of different creatures will be attracted to your garden: this will result in a balanced situation and you will hardly have any problems.
There are hundreds of species of these sap-sucking parasites, including the green aphid and the black aphid, but they rarely cause serious problems. If you have plenty of them, pass the stems through your fingers to crush them, or sweep them away with a jet of water.
They are sap sucking insects, more common in greenhouses, which can be controlled using flypaper or biological methods.
They attack many plants, especially brassicaceae. Cover them with non-woven cloth to prevent butterflies from laying eggs or simply remove the caterpillars as they appear.
Small beetles that move in jumps and form small holes in the leaves and stems. Their larvae eat the roots weakening the plants, which should be protected with transparent bells or non-woven fabric. A rotenone-based insecticide powder is effective.
Serious disease of brassicaceae and some edible roots that causes swelling of the roots. If the cabbages wither for no apparent reason eradicate one and observe the roots. If you find the hernia, uproot them and burn them all. Useful for crop rotation (see page 30) and soil alkalinization (pH higher than 7).
The best way to get rid of them is to go to the garden at night with a torch and eliminate all those that are found.
For red snails, poisoned bait is also effective.
White powder due to fungi growing on leaves and stems. To prevent it, water it abundantly and facilitate air circulation.
This damn parasite mainly infests the brassicaceae. Adult insects lay their eggs next to plants and the larvae get stuck in the soil, where they wither the roots causing withering and stunted growth. In order to prevent the larvae from digging, transplant the seedlings through a layer of lance lying on the soil, or surround them with a 10 cm diameter felt ring.
Diseases caused by fungi that cause discoloured patches on the top page of the leaves and grey growths on the top page of the leaves lower. Prefers hot and humid conditions. Improve air circulation and water at the base of plants; destroy affected leaves.
Potato and tomato downy mildew
This infectious disease causes brown spots on the upper side of leaves and stems and white spores on the lower side. To prevent it, buy resistant arieties. Spacing the plants with a nebulizer and wetting the greenhouse floor.
Mushroom disease that attacks only a few plants, including leeks and beans, forming yellow or brown pustules on the leaves. It does not cause any problems, so ignore it.
Mice eat freshly planted pea and bean seeds. Use traps or sow in abundance to compensate for losses.
Especially pigeons attack young seedlings. Use scarecrows or nets. Wire mesh cages are ideal.
There are many types, all incurable. Usually they manifest themselves with stunted and distorted leaves, unusual discolouration and appearance of drawings on the leaves. They are propagated by aphids or gardening tools. In case of virus attack, eradicate and destroy the affected plants.