Grape mildew disease: treatment and photos, treatment, how to treat

Author: Elena N. https://floristics.info/ru/index.php?option=com_contact&view=contact&id=19 Category: Plant Diseases Published: March 20, 2017Last edits: July 21, 2020

Mildew preparations (fungicides)

Folk remedies for combating grape mildew

Grape varieties resistant to mildew

Literature

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Mildew, or downy mildew of grapes , is the most common and harmful disease of European crop varieties, affecting all ground organs. The disease is caused by the fungus plasmapara viticola, which was brought from North America to France in 1878 and eventually spread throughout the vineyards of Europe. It was the appearance of this disease that caused the decline of European viticulture at the end of the 19th and beginning of the 20th centuries.

Mildew disease - description

Grape mildew is manifested by the lightening of the affected tissues: on young leaves, oily, yellowish transparent spots the size of a small coin are formed, while on older leaves the spots have angular outlines and are located mainly along the veins. Soon, a white powdery fluff - mycelium - appears on the underside of the leaves under the spots. The spots spread to all green organs of the plant - tendrils, shoots, ridges, inflorescences and young berries.

Affected inflorescences turn yellow and curl, and subsequently turn brown and dry out. The berries turn blue, darken and wrinkle - they become leathery and unsuitable for food and winemaking. Leaves disfigured by mildew fall prematurely, and diseased shoot tips dry out.

The rate of development of the disease depends on the air temperature: at 20-25 ºC, signs of mildew appear on the fourth or fifth day, and if the weather is cooler, symptoms will appear later. The disease progresses in conditions of high humidity. Damage from the disease in the absence of protective measures can amount to 50% of the crop.

Plant protection without chemicals

Mildew - causes and harmfulness

As we have already mentioned, the causative agent of the disease is a microscopic parasitic fungus, Plasmopara viticola, from the class Oomycetes.

The fungus overwinters as an inactive spore inside fallen leaf blades and berries (the viability of such spores can persist for two years). Once it hits the host plant, the disease cycle begins.

For the reproduction and spread of the pathogen, a warm and humid environment is required (optimal conditions are 25 ° C and humidity above 85%), preferably in the absence of direct sunlight (in the shade or at night) - only under such conditions do spores germinate well and form numerous threads -seedlings intertwined into a mycelium inside the plant tissue (entering through the stomata). These seedlings (microconidia) easily break off from the mycelium and are carried by the wind for tens of kilometers.

In dry weather, sporulation of the fungus is difficult or does not develop at all. That is why the vineyards of the south of Central Asia suffer little from this scourge.

The fungus is capable of developing on absolutely all green vegetative organs (leaves, young shoots, buds and inflorescences, unripe fruits), which over time turn brown, wrinkle and dry out. But already colored berries do not get sick.

During its life activity, the pathogen disrupts the vital activity of plant cells and destroys chlorophyll, as a result of which grape plants are severely weakened, and the yield is reduced by up to 50% (inflorescences affected by the pathogen do not produce ovaries, and the berries quickly dry out). In the collected remaining berries, a thickening of the peel, a change in color, a decrease in sugar content and an increase in the acidity of the juice are recorded. In addition, the disease leads to a noticeable weakening of the frost resistance of the grapevine. In the absence of prevention and control measures, the infection can completely destroy the crop.

Additional reasons contributing to the infection of grapes with plasma parasites may be:

excess nitrogen fertilizers;
untimely garter of young shoots;
crown thickening;
early pruning of bushes;
susceptibility of the variety to the disease.

Mildew or oidium

In addition to mildew, a common disease of grapes that can destroy up to 80% of the crop is oidium, or powdery mildew. These diseases differ from each other in that on the upper side of leaves affected by oidium, not oily spots appear, but a whitish coating. Under this coating, if you wipe it off, you can find brown spots. Another distinctive feature of oidium is the smell of rotting fish.

Causes of fungal progression

Spores spread quickly, facilitated by natural factors, such as wind, rain, dew. Once exposed to a moist environment, they germinate and then penetrate the plant tissue. This is the main and main reason for defeat.

At the same time, there are certain factors that ensure progress:

the crop has young green leaves up to 5 cm in size;
soil temperature - above 12 degrees;
rainy season;
The air temperature at night does not fall below 10 degrees, during the day - not less than +18 °C.

If both main factors (heat and moisture) act together, reproduction occurs faster. Fixing the problem once is not enough. In some cases, secondary infection is possible during the season.

A repeat outbreak next year is expected if the gardener does not take into account certain nuances: spores can overwinter on the surface of fallen leaves and then spread in the spring. Experienced gardeners recommend burning leaves in the fall.

Mildew - treatment

Mildew control measures

If you grow European grape varieties, you will still have to take measures against mildew. The fight against mildew primarily involves the use of chemicals, but disease prevention and grape care measures are also important. If the vines are planted spaciously, this promotes good ventilation and quick drying of the bushes, and, therefore, reduces the risk of the spread of infection. It is very important to promptly remove stepchildren and excess shoots, tie up growths and regularly remove weeds.

Treatment of grapes against mildew

Treatment of grape mildew is carried out with antifungal agents containing copper. Among them there are drugs that are washed off with the first rain, and there are those that have a long period of action - up to three weeks. A significant portion of fungicides contain copper, which is the most suitable and inexpensive means of combating mildew, but some grape varieties respond poorly to treatments with copper-containing preparations, especially during flowering.

Downy mildew - treatment on different crops

How to treat mildew on those grape varieties for which the use of copper is contraindicated? There are a number of anti-mildew products called organic fungicides. They do not contain copper, and yet cope well with real and downy mildew. They are based on active ingredients such as captan, maneb, zineb, mancozeb, thiram, cynos and others. These drugs are marketed under different names.

Today there are also mildew fungicides on sale that are a combination of an organic fungicide with sulfur or copper, and sometimes with both substances. The presence of sulfur in the preparation allows you to destroy the infection literally in one treatment, and the combination of copper with organic matter softens its destructive effect on grape varieties sensitive to copper.

In the fight against severe mildew, such drugs of contact and systemic action as Ridomil Gold, Champion, Quadris, Cabrio Top have proven themselves well.

Septoria / Septoria

Mildew disease - prevention

Preventive measures help significantly ease the fight against mildew on grapes. The first preventive treatment is carried out in the spring, immediately after tying the vines to the support. The grapes, the ground under the bushes and between the rows are treated, after which the area is mulched to suppress the spread of infection. Solutions of Bordeaux mixture, Oksikhom, Abiga-pika or other drugs prepared in accordance with the instructions are used as preparations for treatment.

Growing grapes in the garden - planting and care

The next preventive treatment is carried out during the appearance of 4-6 leaves. Since Bordeaux mixture suppresses the development of young growth, it cannot be used at this stage. For spraying, the preparations Polychom or Polycarbacin are used. In 10 liters of treatment solution, prepared in accordance with the instructions, it is advisable to add 80-90 g of colloidal sulfur, which will protect the grapes not only from mildew, but from oidium and even from mites. In addition, sulfur stimulates the formation of leaves.

Before flowering, grapes are treated with solutions of Tiovit Jet, Topaz or Actellik, and after flowering, when the fruits are already the size of small peas, it is necessary to spray the bushes and the soil under them with a solution of a contact-systemic drug, which include Thanos, Ridomil Gold, Acrobat and others.

Try to alternate fungicides, since one of the main disadvantages of some of them is the development of resistance, that is, the fungus getting used to them. That is why each of the drugs can be used only once per season.

During leaf fall, the grape bushes are pruned, after which all leaves, cut shoots and branches are burned. Before sheltering for the winter, the grapes and the soil under them are treated with a solution of 1 kg of salt or 200 g of urea in 10 liters of water.

Symptoms and course of the disease

Mildew, also known as downy mildew, affects the above-ground part of the plant, quickly spreading to neighboring bushes. To detect the disease in time, you need to know what mildew looks like.

At an early stage, the fungus covers the foliage of the plant:

the upper surface of the leaf plate becomes covered with oil stains with a yellowish tint;
on the back side the foliage is affected by a whitish fluffy coating, forming a mycelium;
yellowness gradually spreads to most of the leaf.

In the absence of proper treatment at the initial stage, the infection is transferred to flowers, shoots, and ovaries of the bush.

Symptoms of infection appear as follows:

grayish or brown spots appear on the shoots;
the inflorescences become covered with a white coating, gradually drying up;
There is a gradual darkening of the ripening fruits, leading to drying out and shedding of the berries.

Attention! Affected fruits should not be eaten or processed to make wine.

The rate of development of the disease is influenced by the climatic conditions of the region. At a temperature of 20-25°C, the initial signs of mildew on grapes are noticeable after 4-5 days. In cool weather, symptoms become noticeable much later.

High humidity accelerates the development of infection. Lack of protective measures can lead to the loss of most of the crop.

Mildew preparations (fungicides)

Of the many fungicidal preparations, the following are most often used in the fight against mildew:

Abiga-pik is a copper-containing contact fungicide with a broad spectrum of action, intended to combat fungal and bacterial diseases of vegetable, industrial, fruit, ornamental and flower plants. Moderately hazardous substance;
Acrobat MC is a systemic-local fungicide used to combat Alternaria and late blight of potatoes, mildew of grapes and downy mildew of cucumbers. Dangerous substance;
Bordeaux mixture is a broad-spectrum fungicide intended to protect vegetable, berry, fruit, melon, citrus, flower and ornamental plants from a range of diseases. Dangerous substance;
Copper sulfate is a copper-containing contact fungicide with a broad spectrum of action, used to combat diseases of ornamental, fruit, berry crops and shrubs. Moderately hazardous substance;
Oxychom is a systemic contact fungicide with a broad spectrum of action against fungi of the oomycete class. Dangerous substance;
Ridomil Gold is a systemic contact drug to combat Alternaria, late blight and other fungal diseases. Dangerous substance;
Quadris is a broad-spectrum fungicide for protecting grapes, indoor and outdoor cucumbers, tomatoes, onions, potatoes, as well as sports lawns from a range of diseases. Dangerous substance;
Cabrio Top is a combined broad-spectrum fungicide specially designed to protect grapes from both oidium and mildew. Moderately hazardous substance;
Thiram is a contact pesticide used to protect plants from phytopathogenic fungi. Preparations based on Thiram belong to classes 2 and 3 of danger to humans;
Polychom is a complex fungicide that effectively protects plants from diseases such as moniliosis, mildew, late blight and other diseases of a fungal nature. Moderately dangerous;
Polycarbacin is a systemic fungicide with protective and therapeutic action, which is used to combat fungal diseases of vegetable and fruit crops. Moderately dangerous.

Prevention of fungal infections

In order not to encounter a problem, you need to take care of the proper prevention of grape diseases. Let us remind you that the techniques described below are effective not only in the case of mildew, but also in other fungal infections.

Main recommendations:

setting up the vineyard in ventilated areas;
row orientation in accordance with wind movement;
regular garter, sanitary pruning and shaping;
periodic application of potash and phosphorus fertilizers;
pruning and pinching;
monitoring the condition of seedlings, removing affected parts of the plant;
planting healthy crops;
selection of varieties resistant to fungal infection.

It is equally important in spring and autumn to promptly remove and burn all plant debris. Watering the bushes is ensured so that the liquid does not touch the shoots and leaf blades. You should unquestioningly adhere to the rules of agricultural technology and carry out planting treatments on time.

Folk remedies for combating grape mildew

If you find signs of downy mildew on grapes at the very beginning of its development, you can try to destroy the infection using traditional methods that are more gentle than fungicides and pesticides. For example:

Viral diseases of indoor plants (part 1)

A liter jar of sifted wood ash should be filled with a bucket of water, left for 5-6 days, then strained, added and dissolved 50 g of grated laundry soap and treated with this infusion on the grapes and the soil under the bushes. This measure is most useful in the second half of summer, and spraying must be repeated every 10 days;
grind a glass of garlic cloves in a meat grinder, add a liter of water, leave for a day in the dark, strain, add 6-7 liters of water, 50 g of laundry soap or liquid dishwashing detergent, 50 g of iodized salt and enough potassium permanganate to make the composition pink. . The treatment is carried out in two stages with an interval of two weeks;
dissolve 5 g of potassium permanganate in 10 liters of water and spray the solution on the underside of the grape leaves, and then dust the upper side of the leaves with wood ash.

Planting dill around your vines will allow you to keep the number of mildew treatments to a minimum, but be careful not to let the dill grow too large.

What kind of disease is this?

Until the 19th century, mildew was known only in North America, where it was found on wild vines. This continued until phylloxera was discovered in France in 1868, at which time a group of scientists moved to America to search for disease-resistant varieties. The expedition was successful, but along with new varieties of crops, the fungus causing mildew was introduced into the country.

The French researcher Cornu was the first to sound the alarm - he pointed out the danger of downy mildew for varieties bred in Europe. But his remark was not taken seriously. After some time, the first outbreaks of the disease were discovered in the south of France, and then the epidemic spread throughout the country. A year later, mildew had already affected the vineyards of the Balkans and the Caucasus. Thus, massive infection of downy mildew caused the decline of viticulture in the late 19th - early 20th centuries.

Reference! Today, the disease is widespread in almost all crop-growing areas, with the exception of places like Central Asia, where there is no precipitation in the summer.

The causative agent of the disease is the fungus Plasmopara viticola, a relative of blue mold. This is an obligate biotrophic parasite - it develops exclusively on living plants. It damages all above-ground parts of the grapes. If the damage is severe, the bushes dry out, lose leaves, the vines on them do not ripen well and the harvest is lost.

Grape varieties resistant to mildew

Among grape varieties there are less and more resistant to downy mildew. Resistance to mildew allows you to reduce the number of treatments of grapes with pesticides, which has a positive effect on the quality of the crop. Such stability is assessed on a five-point Gusfeld scale. For example:

a score of 0 points is given to varieties that are not damaged by the disease at all and, accordingly, do not need protection from mildew;
1 point – for varieties in which no more than 5% of the leaf apparatus is affected, therefore there is no need for chemical treatments either;
2 points are given to varieties that are affected by mildew by no more than 10%, and they also do not require chemical protection;
3 points are given to relatively hardy varieties that require no more than two preventive treatments per year, since without spraying with fungicides up to 25% of the crop can be lost;
4 points for varieties susceptible to mildew, which should be treated with chemicals 4-5 times a year, since without fungicide treatments, crop losses can be 50%;
5 points for highly susceptible varieties, the damage to which by mildew can reach 100%, and therefore chemical treatments should be carried out after each rain.

Almost all Euro-Asian grape varieties are highly susceptible (5 points); new Euro-American varieties and other more complex hybrids have mildew resistance of 3, and sometimes 2 points. The best mildew-resistant varieties are:

Golden Resistant is a highly productive, frost-resistant table variety of early ripening, which is almost not affected by mildew, oidium and gray rot. The berries of this variety are medium in size, white with a golden blush on the sunny side, the pulp is juicy, with a fresh, harmonious taste;
Dniester pink is a frost-resistant, late-ripening, productive variety with medium-sized dark pink berries with dense pulp and simple taste;
Buffalo - a frost-resistant American variety with medium-sized black oval berries with a bright strawberry flavor and a tart aftertaste;
Pineapple is another American variety characterized by high winter hardiness and relative resistance to mildew. The berries of this variety are large, yellow-green, the skin is thick, the flesh is slimy, pleasant to the taste, with an aroma reminiscent of the smell of pineapple;
Cardinal is an early ripening Californian variety with large berries weighing 8-10 g, very pleasant taste with a nutmeg aroma;
Talisman is a frost-resistant early-medium high-yielding table variety with large (12-16 g) white berries of harmonious taste, acquiring a nutmeg aroma when fully ripe.

In addition to those described, grape varieties such as Podarok honey, Podarok Zaporozhye, Alexa, Bazhena, Muscat noble, Nistru, Original and others are resistant to mildew to varying degrees.

What harm does the disease cause to grapes?

Mildew causes enormous damage to the vineyard, so the gardener in this case suffers considerable material losses.

There is a huge loss of berry harvest. It can reach up to 50-90%.
The taste qualities of grapes and, in connection with this, processed products (juices, wine) are significantly reduced.
It is inadmissible to prepare high-quality planting material.
Grape bushes weaken, do not tolerate winter well and often die.
Yields will decrease next year.

Review of popular fungicides

There are nine fungicidal drugs that are considered the most effective in combating mildew.

"Abiga-pik"

“Abiga-pik” is made from copper oxychloride, which acts on fungal spores and destroys them. It is recommended that you familiarize yourself with the application features of the product in order to use it correctly.

First, a working mixture is prepared from it, which will be used when treating a diseased grape bush. 50-70 milliliters of fungicide are mixed with water. In this case, it is better to use a heated liquid, since Abiga-pik dissolves better in it. The bushes are sprayed with the solution every three weeks throughout the season.

"Acrobat MC"

This medicine is indispensable in the fight against late blight, powdery mildew, Alternaria and other fungal infections. "Acrobat MC" is sold in the form of granules that can quickly dissolve in warm and cold water. They are made from mancozeb and dimethomorph, which eliminate the causative agents of fungal diseases.

To prepare a working solution from Acrobat MC, dissolve one capsule in 8-10 liters of water. Sometimes two pieces are added at once to make the mixture more concentrated.

Bordeaux mixture

To get rid of powdery mildew and save grape bushes, you can spray with Bordeaux mixture. To make it, slaked lime with copper sulfate is used. The components are mixed in equal proportions. The resulting composition has disinfecting properties, thanks to which it is possible to get rid of dangerous microorganisms on plants.

The first treatment is carried out during the swelling of the buds on the stems. The next time the plant is sprayed with the product during the growing season. In this case, use a weak one percent fungicidal composition.

Copper sulfate

Powdered preparation made from copper sulfate. Used by gardeners to cure vegetables and garden crops from fungal diseases. The advantages of copper sulfate include its long-lasting protective effect, as well as its effectiveness.

To treat one hundred square meters of vineyard, you will have to prepare ten liters of working solution. To do this, add 90-10 grams of the substance to the water. You cannot add more copper sulfate, as in large quantities the product will harm the plant.

"Oxyhom"

Powdered fungicide, which is used for foliar treatment of vineyards and other garden plants. This is a two-component product made from oxadixil and copper oxychloride. Substances from Oxychoma negatively affect pathogenic flora and gradually destroy them. Thanks to this, it is possible to get rid of powdery mildew and cure the grapes.

When creating a medicinal product, add 20-25 grams of powder to 10-14 liters of water. Everything is thoroughly mixed, after which the plant seedlings are sprayed.

"Ridomil Gold"

It is no secret that fungal diseases are very dangerous and must be gotten rid of immediately. Ridomil Gold will help cure grape bushes that are sick with powdery mildew. This fungicide is a contact agent, since it begins to act on plants only after contact with pathological microflora.

The product is mixed with water in a ratio of one to ten. The prepared composition must be consumed within five hours after preparation, before it begins to deteriorate.

"Quadris"

To protect vineyards from fungal diseases, you can use “Quadris”. This is a universal remedy that is used when growing vineyards in protected or open ground. “Quadris” can be sprayed on grapes, cabbage, potatoes, legumes, onions, garlic and other vegetable crops.

"Convertible top"

Granular fungicide, sold in twenty-gram sachets. The main advantage of Cabrio Top is that it is able to protect vineyards from downy and powdery mildew. The medicine also contains components that make it possible to cure anthracnose, rubella and escoriosis in plants.

It is recommended to use the product during the flowering of plants, before clusters of berries begin to form. Spraying is carried out every two weeks, since the protective effect of the fungicide lasts only 15-16 days.

"Tiram"

This is a protective fungicidal drug that does not penetrate plants and suppresses spores located on stems and leaf blades. "Tiram" is distinguished by its contact action, and therefore it will not protect against diseases that develop inside seedlings. Because of this, experts advise using the product only when fighting mildew at the initial stage of development.

To create an effective working mixture, “Tiram” is mixed with water in a ratio of one to five. Plant treatment is carried out at the end of spring and in the first half of summer.