Powdery mildew : how to fight and treat your plants ?

Powdery mildew is among the plant diseases which bother all people closely or remotely linked to the culture. At the beginning of damage considerable effects it causes on plants of all orders, this white rot sometimes named white disease must be dealt with as soon as possible. It is also possible to prevent it thanks to a few relatively simple solutions to apply. Let’s take stock of powdery mildew, a cryptogamic disease to be taken seriously and the best means to take into consideration to save your plantations.

Powdery mildew: a cryptogamic disease

Oidium is a term that designates different fungal or cryptogamic diseases since the culprits are fungi. They target many plants. The phytopathogenic fungi responsible for this disease also called white rot are part of the Ascomycetes division (Ascomycota) whose forms are extremely varied, belonging to the family of Erisiphaceae and genres Sphaerotheca, UncinulaErysiphe et Podosphera.

Powdery mildew parasitizes countless plants, from tomatoes to maple, from vines to ornamental plants, including clover or even citrus fruits, crucifers… This “powdery mildew disease” is a real scourge for agriculture. as for the vegetable garden, the fruit tree and the ornamental garden.

White rot or powdery mildew: conditions most favorable to the disease

To develop, powdery mildew needs special conditions. The proliferation of phytopathogenic fungi is amply favored by a hygrometry (humidity level) high around 75% despite a temps sec. These are conditions that are found more specifically during the second part of spring, when the heat begins to set in but the humidity is still quite substantial and when, in addition, there are temperature differences relatively large between the night and day periods.

The disease which settles among other places within the buds resists perfectly in these organs throughout the winter. When the resumption of vegetation the young shoots are formed, they are then fully infected with powdery mildew. They are given the very specific name of “flag pushers”.

Powdery mildew: the signs to spot

Whatever plants are affected by a powdery mildew parasitic attackthey show the following signs:

  • A greyish white powder which looks like flour and forms a kind of felt on the aerial parts of plants, that is to say:
    • The stems,
    • Leaves,
    • The buds,
    • Flowers,
    • The fruits.
  • A leaf deformation of the host plant, such as blistering, curling, curling. It should be noted that in some plants it is first of all the young leaves that are affected, while in others, powdery mildew deforms the old leaves, which more specifically threatens late harvests.

This cryptogamic disease, in addition to causing the withered leaves then their chutecan significantly reduce yield if left untreated or cause serious disfigurement on ornamental plants.

Powdery mildew or white rot: solutions for treating plants

Let’s review the different means of combating powdery mildewtheir advantages and disadvantages.

The 22 point ladybug

Psyllobora vigintiduopunctata is a small beetle of the family of Coccinellidae. It is a 22-point ladybug which has the particularity of feeding exclusively on ascomycete fungi responsible for powdery mildew disease.

However, its usefulness may be questionable insofar as the ladybug can contaminate other plants by moving from plants affected by powdery mildew to healthy plants. There is therefore an interest in using this beetle only if all the plants in the garden are affected by white rot…

Bicarbonate of potassium

This is a non toxic product, economical and biodegradable which gives good results in the fight against cryptogamic diseases. He neutralizes the acidity of the environment in which phytopathogenic fungi proliferate. Thanks to its antifungal action, potassium bicarbonate therefore eliminates powdery mildew.

On the other hand, it can be criticized for taking on moisture in just a few hours so that it solidifies and then becomes very difficult to use.

Le bicarbonate de sodium

Made from natural minerals, what is commonly (and wrongly) called baking soda, is actually thehydrogénocarbonate de sodium. It is among the most used treatment products to effectively eradicate powdery mildew. In addition to being very inexpensive to buy and easy to use, it is do not pollute. It is the gardener’s perfect ally because it can be used in the orchard and vegetable garden as well as on ornamental plants.

A sulfur product

Of the sprays are necessary to stop the development of white rot but they must not be carried out when there is a lot of sunshine as this causes burns on the leaf system.

Sulfur is a plant protection product which can be applied in powder form to plants or after dilution, strictly compliance with the recommended dosages by the manufacturer. It is necessary to buy an approved sulfur product that can be used as a fungicide on the infested parts of vegetable plants, fruit trees, ornamental trees and plants with flowers or decorative foliage.


Diluted 10% in waterthe whey should be sprayed regularly on the leaves when the light is strong. It is therefore preferable to treat in bright sunlight because the light causes a particular phenomenon: peroxide radicals are formed under its action in the milk serum. Powdery mildew is not resistant because these radicals are highly toxic for this powdery mildew disease. Note that we can use skimmed milk instead of whey.

Milk treatment against powdery mildew requires that this 10% dilution be respected. It should indeed be known that other families of pathogenic fungi can develop in the event of an overdose.


If the where a few plants to treat, it is possible to prepare a homemade treatment product, namely an infusion of garlic because of its sulfur compounds. We add to it a bit of milk for its antifungal properties but above all because it acts as an adhesion adjuvant, in other words a kind of natural fixer.

Horsetail decoction

Horsetail, nicknamed ponytail is mistakenly considered a “weed”. On the contrary, it is a very useful wild plant against powdery mildew. Just cut its stems and then dry them in the sun. Then macerate 100 g of dry horsetail in 2 liters of water for 3 hours. This mixture must then be boiled for 20 minutes. Once cold, all you have to do is filter it before using it by spraying it after diluting it at the rate ofone part horsetail decoction to four parts water.

It is recommended to repeat the treatment regularly. It is better to prepare its decoction just before each use because this mixture does not keep for very long.


Admittedly hyper effective even in the event of a heavy infestation of powdery mildew, bleach has a major drawback : it radically destroys the fauna and flora that live in the earth. However, these are absolutely essential to ensure the fertility of the soil. We therefore keep our hands ultra light with this type of treatment, and as far as possible, it is better to give preference to other solutions.

Powdery mildew (powdery mildew): means of prevention

Some actions can be taken as a preventive measure. You can for example:

  • Respect a sufficient space between the plants at the time of planting so that the degree of humidity that is moderate,
  • Apply with regularity preventive solutions on all plants known for their sensitivity to powdery mildew,
  • Water at the foot and take care not to wet the foliage or the flowers,
  • Allow air to circulate in the heart of the plantations by performing a regular weeding around its crops.

It is recommended to always take precautions when we have to treat your plants, regardless of the product used, which includes natural treatments. It is necessary to wear gloves, a mask but also protective glasses in order to limit the risks of burns by contact but also to avoid inhaling these products which can prove to be irritating. Be especially wary of sulfur vapours.

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