Powdery mildew vine

Powdery mildew vine

Powdery mildew vine

It is one of the most fearful diseases of the vine and also the most difficult to fight. We are talking about powdery mildew, also called bad white or "fog". The disease affects several plants, but prefers the vine, assuming epidemic and large-scale dimensions. When the vine is hit by powdery mildew, it does not die, but suffers a serious impairment of its vegetative development, both in flowering and in fruiting. The leaves and shoots also appear strongly weakened. The powdery mildew of the vine is generally fought with adequate preventive strategies and specific curative products. There are also biological control methods, but it is important to intervene early, because powdery mildew tends to recur often in the same crops.


The powdery mildew of the vine is caused by a fungus belonging to the Erysiphaceae family. The infectious agent can belong to different families, the ascomycetes and the oidiums. In both cases, the damage and symptoms caused to the vine are always the same. The vine can, in fact, be indifferently attacked by the Uncinula necator, an ascomycete fungus, and by the Oidium Tucker, a fungus of the genus Oidium. The pathogen originates from North America and was accidentally introduced in Europe in the nineteenth century. Since then, millions of plants have been affected, with serious cultural and economic damage due to the high spread of this disease and its ability to recur promptly during each growing season. Powdery mildew does not penetrate inside the plant tissue of the vine, but attacks it from the outside, covering it with its mycelium, the reproductive organ from which new generations of fungi overwinter. The mycelium attacks the vine in all its structures: shoots, leaves, flowers, buds and berries. The disease only prefers young plants, while it does not manifest itself in any way in adult or older ones.

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The grapevine affected by powdery mildew develops a greyish white patina in the diseased parts that gives off a strong smell of mold. At the beginning of the infection, the leaves of the plant take on a translucent color with yellowish spots, similar to oil, and a flag shape. Subsequently they are covered with the white patina, they curl up, dry up and fall. The same mechanism can also occur in the other parts of the plant, in the flowers, in the shoots and in the berries. In these cases, in addition to the white mold, other typical colors are formed, such as the brown of the branches or the blackish of the berries. The flowers and buds, on the other hand, are unable to complete their maturation. The berries and shoots may also have cracks, while signs of necrosis of the plant tissue are also evident. The damage of the powdery mildew of the vine can be both direct and indirect. The former relate to the symptoms we have just indicated and which lead to an impairment of the fontosynthetic capacity of the plant and a poor development of the fruits, while the latter concern the transmission of viruses, fungi and bacteria that are inoculated into the plant with the mycelium of the fungus. .


The causes of hatred are attributable to particular climatic and temperature conditions. The powdery mildew fungus usually winters at temperatures between twenty and twenty-nine degrees, while it is unable to reproduce at temperatures above thirty degrees. Humidity does not seem to be responsible for the development of powdery mildew, because this fungus does not need water to spread. However, the combination of heat and humidity can favor the development of other fungal diseases transmitted indirectly with the mycelium of the oidium. The periods of powdery mildew attack are concentrated between flowering and fruit ripening.


Powdery mildew can be prevented by regularly pruning the vine and eliminating the excess parts that cause an increase in temperature and lack of light inside the plant. Since the mycelia of the powdery mildew fungus tend to survive in the pruning material, it is always better to burn the removed parts. Sometimes, in the period of pre-flowering, it may be useful to carry out a preventive treatment with antifungal products. The products should be administered during the cooler hours, in order to let them act longer and not damage them with the action of the sun's rays. Periodically and during the phases most susceptible to powdery mildew attack (flowering, potting and fruit setting), all the various parts of the plant must be carefully checked, in order to apply preventive products in time.


The fight against the iodine of the vine is carried out with antifungal chemicals (preparations based on copper and sulfur) and with fungi antagonists of powdery mildew. Preparations based on copper and sulfur can perform a preventive action against both powdery mildew and downy mildew, while with full-blown disease (powdery mildew only) only products based on wettable or powdered sulfur should be used. Sulfur must be compulsorily administered before flowering, in order to carry out an effective preventive action. Other useful products for powdery mildew are Dinocap, a nitrophenol-based fungicide and IBS (inhibitors of sterol biosynthesis). The latter are composed of irimidines, pyridines, piperazines and triazoles. IBS can be administered alone or mixed with sulfur. Chemical products against powdery mildew should be administered no more than three times a year, to prevent the disease from becoming resistant. The biological fight against powdery mildew is carried out through the use of Ampelomyces quisqualis, an antagonist fungus that neutralizes the pathogenic mycelium of its "fellow". The antagonist mushroom can be used alone or mixed with mineral oils. In this case there will be not a biological fight, but “integrated” with other chemical products.

Powdery mildew

With the term powdery mildew we identify a trophic disease of plants. This type of disease is caused by the subtraction of nutrients from plant cells by pathogens. In the case of powdery mildew, the pathogenic agents are microscopic fungi called Ascomycetes, belonging to the family of Erysiphaceae. These are fungi that are not visible to the human eye.

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Oidiospore under the microscope

Their characteristic is to produce filaments from which later spores, called oidiospores.
The pathogens of powdery mildew establish a defined trophic relationship with the plant obligate parasitism.
This means that without the nourishment obtained from the plants, the fungus would not survive, especially during the winter latency. The new spores are usually released by the fungus in early spring. Due to the action of the wind, the infection moves from one plant to another.
A further characteristic of powdery mildew is that each species of pathogenic fungus attacks a specific family of plants on different parts of the plant through the development of a mycelium.

Powdery mildew attacks many garden plants including beets, radicchio, endive, carrots, celery, parsley, fennel and also cereals such as buckwheat and barley, as well as fruit trees, for example apple, vine, and the peach tree.

As for garden plants, the species most sensitive to powdery mildew are lilac, begonia, rose, maple, plane tree, laurel, hawthorn, hydrangea, chrysanthemum, dahlia and calendula.

Fungicidal bicarbonate spray

To prepare a bicarbonate spray with fungicidal power you will need:

  • 1 liter of water
  • 4 g of baking soda
  • 1 spray container


Add about two tablespoons of baking soda (4 grams) to a liter of water and mix so that it dissolves completely, then pour into the spray container and apply to the plants with a gentle spray (in fine drops). The bicarbonate fungicide must be applied to the entire aerial part of the plants and in particular to the leaves on both the upper and lower parts.

Two weekly applications are recommended during the periods of the year in which there are low temperatures and high humidity, or those in which the most favorable conditions are created for the development of fungi.

It is very important to prepare only the amount necessary for use from time to time, that is, it is not advisable to make the spray in advance and keep it for more than a day without using it as in this way the mixture will lose its healing properties.

Do not worry about the possible harmful effect of baking soda on plants, this ingredient in fact does not cause any wilting or even death of any flower or crop. The only important thing is never to irrigate the land with water and bicarbonate but only spray on the plants.

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How to eliminate powdery mildew and scab in a biological way

A novelty this year is theSodium hydrogen carbonate: a white crystalline powder, based on Hydroxycarbonate of Sodium, which has the ability to create an unfavorable environment for fungal proliferation and therefore protects plants from the attack of Powdery mildew is Scab.

It acts by contact, raising the pH on the leaf surface, causing the walls of the fungal cells to collapse and dehydrating the spores. Precisely because of this multiple mode of action, theSodium hydroxy carbonate it has a low potential to favor the onset of resistance.

It protects ornamental plants but also edible ones with a very short harvesting interval (1 day).

It can be used to combatPowdery mildew of the Lives, of the Strawberry, of the Cucurbits, of the Currant, of the Apple tree, ofGooseberry, of the Raspberry, of Vegetables and of Aromatic.

Its use is allowed in organic farming.

To use it, simply dilute 3-5 grams of the product in 1 liter of water for ornamental plants and vegetables. For application on fruit trees and vines, dilute 50-100 grams of product in 10 liters of water. Repeat the treatment after a week.


A vine mold, that is a trophic disease that infects plants and that is caused by a particular type of fungi (Ascomycota) belonging to the Erysiphaceae family is commonly known by the name of white disease, fog, albugine or powdery mildew.
This mold of the vine is characterized by a relationship, which binds the agents of powdery mildew to the vine, attributable to obliged parasitism, that is, that form of symbiosis in which the mold of the vine takes advantage at the expense of the vine itself by creating biological damage.
The mold of the vine is observable through the formation of a felt, characterized by a whitish color and an appearance that seems dusty, which covers the organs of the vine that have an intense vegetative activity, such as leaves, buds or fruits, such as for example bunches of grapes.
The mold of the vine, during the attack it carries out against the host plant, firstly causes a discoloration of the affected areas and subsequently the necrosis of the tissues which progressively leads to the formation of desiccation and cracks. The berries that are attacked by the vine mold tend to completely lose the elasticity of the epidermis, tearing and subsequently favoring the entry of other pathogens.
Vine mold usually spreads in spring and early summer, when temperatures are moderate. Its diffusion is facilitated by the wind, while the rain has a contrasting action since it causes the washing away of the mycelia of the mold from the vine.
Traditionally, the defenses taken against this vine mold are based on sulfur-based treatments, which interfere with the germination of molds on the vine, stopping the infection from the initial stages.

Video: PLB 112 - Downy Mildew SQ17