Downy mildew: treatment and prevention of your plants


Downy mildew is among the major concerns of the gardener because it can affect all types of plants, from home garden vegetables to ornamental plants in pots or in the ground. In some cases, we can even speak ofepidemic the problem is so important, especially for market gardeners for example. This term designates several cryptogamic diseases formidable if we do not react from the very first manifestations. Fortunately, there are treatments against mildew but also simple solutions to adopt on a daily basis to prevent its appearance. Let’s take stock, not without having first drawn up a summary portrait of downy mildew.

Particularities of downy mildew

Various fungal diseases are designated by the generic term downy mildew. They are caused by fungal microorganisms. These parasites are among the Oomycetes and have many similarities to pathogenic fungi.

The main ones symptoms presented by the affected plants are:

  • Cotton-like, white mold,
  • Brown spots,
  • The wilting of any affected part, whether it is a stem, a twig, a few leaves or all of the foliage, the tuber, the fruit, then the whole plant,
  • Necrosis,
  • Rapid rotting,
  • A powerful smell.

The plant affected by mildew sees its growth disturbed. If left untreated, it is doomed to certain death and the disease attacks other plants.

Natural treatments against mildew

We have a whole arsenal of fungicides allowing to fight against an attack of mildew, but rather than opting for a chemical product, it is better to resort to natural solutions such as for example:

  • The Bordeaux mixture : it is preferably used just after a heavy rain because this type of bad weather favors mildew. But beware, Bordeaux mixture modifies the hydrogen potential of the soil (pH), which can be extremely detrimental for crops. We therefore recommend using it with a lot of moderation.
  • The Tansy : it must be sprayed on the plants. The preparation consists of infusing 200 g of Tansy flowers (Tanacetum vulgare) in 2 liters of boiling water. It is of course necessary to wait for the perfect cooling of this potion before treating the subjects affected by the mildew.
  • The black soap (2 teaspoons) associated with theoregano essential oil (40 drops), all mixed first in 30 cl of lukewarm water then added to 2 liters of non-calcareous water where care was taken to dilute 4 teaspoons ofclay green or white. This anti-mildew preparation is used cold, in sprays.
  • Of black soap (20 ml) associated with sodium bicarbonate (5 g) in 2 liters of water, to be sprayed on the plants, knowing that after a rain it is necessary to treat again.

Before embarking on any of these proven home recipes, it is imperative to first ensure that it is perfectly suited to the plants concerned, and how often to apply the treatment. However, we can be reassured since these four remedies do not present any particular toxicity for plants. You can also cross your fingers so that the outside temperature rises sharply, the hot weather getting the better of mildew in record time. The reason is simple: during a heat wave, there is hardly any humidity in the air and the soil is dry.

Prevent mildew to protect your plants

When you want to have a productive vegetable garden or a beautiful pleasure garden, you have to know how to treat your plants quickly in the event of mildew. This is fundamental because the various fungal diseases designated by this generic name can affect potatoes, tomatoes, eggplants, peppers, chervil, lettuce, onions, spinach and melon as well. or the vine. In the pleasure garden, a number of plants do not escape it either, as is the case with wallflower, fragrant parsley or even sweet pea among others.

A few days may be sufficient for ruin all efforts if mildew is rife, you might as well not give it the opportunity to take hold. The gardener therefore has every interest in taking good gardening habits in order to play the card of prevention. To do this, it needs:

  • Opt for the crop rotation in order not to cultivate several years in a row the same plants in the same place, in particular all those which are sensitive to downy mildew.
  • Plant resistant varieties.
  • Perform reasoned watering, excess humidity being a serious factor in fungal diseases.
  • Space the plants sufficiently in order to allow the air to circulate properly, the confinement of the plants increasing the humidity rate.

If we cultivate vine, it is strongly recommended to carry out a liquid manure spray horsetail as a preventive measure. Effective on the vine, this solution does not seem to have the desired effect on other plants.

It is of course also very useful to learn how to spot the first signs of mildew to act without delay by cutting all the affected parts which should then be burn, with the aim of preventing the spread of the disease. This plant debris should in no case be inserted into the compost of course, because the spores remain there very well and the next time it is spread, this would only have the effect of infecting the plantations.

Downy mildew should not be treated lightly because the damage that it causes are very important. We cannot, moreover, evoke it without recalling the ravages which he trained in large potato crops in Ireland between 1845 and 1849, responsible for the ” Great Irish Famine Which lasted until 1951. But there it was a terrible mildew epidemic and thedestruction of local cultures was almost total, creating a disaster at different levels: human first since it is estimated that a million people died, then economic and also cultural.