Parassiti e malattie dell'orto

A practical and essential guide to recognize the main diseases that can affect your vegetable garden

Serious diseases are not common in the vegetable garden, especially if it is well cared for, and you probably won’t have to deal with anything more serious than an invasion of plant lice or a minor case of downy mildew or blight.

How to stay out of trouble

Usually in the case of plants with disease, it is easier to eradicate and burn them rather than save them by using chemical products. Vegetables are not plants that last a long time, therefore, you can easily retry to plant them. In this article you will find a list of parasites and of the most common diseases.

Remember that your vegetables don’t have to be affected by them, just because they are in the list, with a little caring and common sense, this won’t happen. The secret of success is to maintain the plant in good health, so that they won't be attacked by parasites or diseases.

If you do not directly plant, buy the plants from a trusted distributor and never transplant them if you think that they might be sick, especially when it comes to brassicas. Make sure that they always are in the best conditions to properly grow: plenty of light, air (but not strong wind), water and nutrients. Do not let the growth of the plants be slowed down by drought: mulch the soil and water it regularly, so that the plants will have enough water and will grow vigorously.

Another important factor is the balance of the vegetable garden. For many many harmful organisms there are specific predators: For example ladybugs, crisope and hoverflies destroy large quantities of aphids, whilst carabid beetles eat red snails and underground larvae. If you have flower beds with many different plants, it is likely that several different creatures will be attracted from your garden: this will create a balanced situation and you will hardly have issues.


There are hundreds of species of these sap-sucking parasites, including the green aphid and the black aphid even though they rarely cause problems. If you have too many, run the stems through your fingers to crush them or spray them away with water.


Only sap-sucking insects, most commons in greenhouses, can be controlled by using fly killer paper or biological methods.


Attack several plants, especially brassicas. Cover them with sheets of non-woven fabric to stop the butterflies from laying eggs or take the caterpillars off as soon as you see them.

Chrysomelid beetles

Small beetles that move in jumps and form small holes in leaves and stems. Their larvae eat roots making the plants weaker, that must be protected with transparent bells or with non-woven fabric. An insecticidal powder based of rotenone is also effective.

Cabbage Hernia

Serious illness of brassicas and some edible roots that causes root swelling. If the cabbages wither without apparent reason, eradicate one and observe the roots. If you find the hernia, eradicate and burn them all. Useful for prevention: crop rotation and soil alkalinization (pH greater than 7).

Red snails and Ladybugs

The best way to get rid of them is to go into the vegetable garden at night, with a torch and eliminate all the ones you find.
Poisoned bait is also effective for red snails.

Powdery Mildew

White powder caused by fungus that grows on leaves and stems. To prevent it, water abundantly and facilitate air circulation.

Cabbage fly

This extremely dangerous parasite affects mainly brassicas. The adult insects lay their eggs next to the plant and the larvae go into the ground, where they gnaw at the roots causing wilting and stunted growth. To avoid the larva digging, transplant your plants through a layer of wool laying on the ground or surround them with a flat ring of a 10 cm diameter.

Downy Mildew

Diseases caused by fungus that causes discolored patches on the upper surface of the leaves and gray growths on the
lower one. It prefers hot and humid conditions. Better the air circulation and water the plants at their base; destroy the affected leaves.

Potatoes and Tomatoes Downy Mildew

This infectious disease causes brown stains on the upper surface of the leaves and stems and white spores on the lower one. To prevent it, buy resistant varieties. Distance the plants with a nebulizer and wetting the greenhouse floor.


Fungal disease that attacks only a few plants, including leeks and beans, forming yellow or brown pustules on the leaves. It doesn’t cause any problem, so just ignore it.


Mice eat freshly planted pea and bean seeds. Use scarecrows or plant abundantly to compensate your losses.


In Particular, pigeons attack young plants. Use scarecrows or nets. Metallic cages are ideal.


There are various kinds, all incurable. Generally they manifest with stunted and distorted leaves, unusual decoloration and appearance of drawings on leaves. They are propagated from aphids or gardening tools. In case of a virus, you should eradicate and destroy the affected plants.

August 26, 2019 — Alias Srl