The scourge of vineyards is diseases and pests. Especially diseases caused by fungi. They are difficult to fight, since spores can wait out unfavorable weather conditions and spread to neighboring bushes at high speed, carried by wind, water, and garden tools. The crops of the affected plants die, and, in addition, the vine does not ripen. And this can destroy the vineyards in severe winter frosts. Therefore, it is necessary to protect the bushes, and in case of damage, quickly identify the pathogen in order to begin timely and intensive treatment of the plants. One of the most common fungal diseases is oidium. Its characteristic signs, as well as medications that will help get rid of the fungus, will be discussed in this article.
Signs of the disease
Oidium is a fungal disease. Its causative agent, uncinula necator, affects various types of grapes and all above-ground organs of the bush. You can learn about grape chlorosis here.
Oidium can be identified by the external signs of the disease:
- Sheet. Spots of grayish-white bloom form on the upper and lower parts of the leaf blade. If the leaves are not young, then brown spots immediately appear that do not have any specific shape;
- Tendrils, inflorescences, buds. Infection can be identified by the appearance of a herring smell in the area of the ashen-colored coating that forms on these vegetative organs. And they dry out and fall off very quickly;
- Berries. A gray coating appears. If the berries are green, then they simply begin to develop poorly and dry out. But when the disease appears during the ripening period of the berries, they crack to the seeds and the bunch rots;
- Escape. A gray coating forms, and underneath there are brown spots that do not have clear outlines. Closer to autumn they change color to reddish-brown.
Oidium, or powdery mildew, is caused by a pathogen that parasitizes only on the living tissues of the grape plant.
Infection can be prevented by timely implementation of agrotechnical measures aimed, among other things, at ventilating the bush.
Mildew or oidium
As mentioned above, oidium for grapes is powdery mildew, while mildew for this crop is downy mildew, or downy mildew. These diseases are very different from each other, and they are caused by different pathogens. What they have in common is that both of these diseases are fungal, and also that they can destroy almost the entire grape harvest. The symptoms of these diseases also differ greatly from each other. A detailed description of the symptoms of oidium can be found above. If the grapes are sick with mildew, then pale yellow oily spots form on the front surface of its foliage; after dew or fog falls, a coating appears on the underside of the diseased leaves, after a while it becomes brown and dries out. Mildew most often affects young foliage of grapes, as well as inflorescences that turn brown, stems (black spots appear on them) and unripe fruits (they become dark in the area of the stalk and fly off). If the grapes do not fly around, they will still have a sour taste. If the bush already has fully ripened fruits at the time of mildew infection, they will not be harmed.
Damage caused
Oidium, mildew, as well as other fungal diseases, cause great harm to vineyards.
Reproduces by spores. The disease develops when high temperatures and high relative humidity occur. The spores, hiding under the scales of the eyes, calmly endure the winter and begin to germinate already at a temperature of 17–19 degrees. But the spores do not like coolness and rain, and their spread may cease under such weather conditions. If fungi have infected grape bushes and you do not fight them, this can lead to the following consequences:
- The berries become unsuitable not only for consumption, but also for the production of wine materials. If they are green, they simply dry out. When ripe, the affected berries simply crack and begin to rot. So cleaning them up for use is useless. This link will tell you about processing grapes in the fall.
- The leaves are drying up. And the processes of photosynthesis do not occur with the intensity required for the bush;
- The vine does not ripen. Therefore, next year the harvest from the bush will be much lower. This is the case if there were no severe frosts in winter. Weakened shoots may simply freeze.
Causes of fungal infection
The fungus lives on the surface of the host plant. A gray-white coating forms on the leaf blades - hyphae. They help the pathogen obtain nutrition from the leaves. Attachment is ensured by suction cups, deep penetration into the epidermis occurs.
After the hyphae absorb all the nutritional components, the leaf dies. Spread occurs due to the transfer of spores by wind blowing to healthy parts of the plant. After contact, the incubation period begins. Within 7-14 days, the fungus penetrates the surface of the leaf.
The following conditions are considered favorable for the spread of infection:
- elevated temperature - from 20 to 25 degrees;
- high humidity;
- long absence of precipitation.
Attention! The reproduction process of Oidium Tuckeri Berk stops at a temperature of 5 degrees. Spores also die in extreme heat (more than 30 degrees). Low humidity is considered unfavorable for the development of spores, so the disease practically does not occur in arid climates.
Treatment
You must not allow the disease to spread in your vineyard. Then you will have to fight it for a long time, using not only sulfur, but also various fungicides, combining them. Therefore, it is necessary to carry out preventive measures, acting strictly according to schedule. In addition, the following preventive measures will help prevent the spread of the disease:
- Harvesting chibouks and own-rooted ones from obviously healthy bushes;
- Plantings should not be thickened. Trimming should be carried out in a timely manner so that the bushes are well ventilated;
- After pruning, the vines in the infected vineyard are harvested and immediately burned.
According to research by employees of the protection department of NIViV “Magarach”, it has been established that effective protection of grapes from oidium is early warning and prevention of infection with the disease.
If the bushes begin to show signs of disease, then preventive methods will not help. It is necessary to treat plants with preparations specially designed for this purpose.
Agrotechnical measures
Agrotechnical measures must create conditions that prevent the development of the disease:
- Proper planning of area for vineyards. They should be placed on slopes or small hills;
- When planting, the rows are positioned in the direction of the prevailing winds. To do this, you will have to analyze the wind rose in advance;
- The culture should be on a trellis. And the higher the sleeves are from the surface of the earth, the better;
- The area must be kept clean;
- Carry out activities aimed at improving the ventilation of the bush: cutting, chasing, pinching, gartering.
The higher the grapes are located on the trellis, the lower the chance of developing the disease.
You need to plant certified grapes purchased from a nursery or from a trusted seller. Own-rooted or chibuki must be from obviously healthy bushes.
Drugs
To get rid of oidium, chemical means of combating the disease are used. Sulfur is especially effective:
- Pollination is carried out with ground sulfur, or a mixture of sulfur and lime - fluff in proportions of one to one;
- Spray with half or one percent lime-sulfur decoction.
The effectiveness of sulfur will be higher, the smaller its particles. Therefore, having purchased the drug, it must be stored in a dry room. When processing, the sulfur cloud should envelop all parts of the plant, including the leaf blade on both sides. This preparation should not be used on vineyards in sunny weather, as burns may appear on the leaves and fruits. This is best done in the evening in calm weather. Sulfur consumption per pollination ranges from 5 to 10 grams. For spraying, dissolve 100 grams of the substance in 10 liters of water. For prevention or mild infection, 50 grams is enough. Read about feeding grapes here.
The fight against oidium is carried out at a temperature of at least 20 degrees and high humidity.
Fungicides
Fungicides are drugs that destroy fungal diseases of grapes, which include oidium. They are divided into the following types:
- Contact. They contain sulfur (Cumulus, Thiovit Jet, etc.);
- System. They penetrate the plant and spread with the juice to all vegetative organs, destroying the causative agent of the disease. They are used during bud break or in the phase of 2–3 leaves. Systemic drugs include Triadimefon (Bayleton), Penconazole, Flutriafol and others.
If the disease is very widespread, then the bushes are sprayed with Triadimenol, Spiroxamine, Trifloxystorobin.
When the areas are large and located far from populated areas, use the drug Tilt-250. They can treat bushes only once a season.
Effective against oidium are Topaz, Skor, Quadris, Falcon.
To prevent the fungus from adapting to a particular fungicide, drugs from different groups are used.
Currently used fungicides in protection against oidium are mainly preventive, and the effectiveness of their use depends on the timing of treatments.
If the grapes suffered from oidium last year, it is worth treating them with Horus or Strobi in the spring.
Folk remedies
Against oidium, the bushes are sprayed with sulfur and fungicides. But there are winegrowers who use traditional methods in the fight against the disease. This could be for various reasons:
- Reluctance to use chemical compounds to keep the berries environmentally friendly. This article will tell you about wine made from grapes at home.
- Slight spread of the disease;
- Material costs for the purchase of drugs, etc.
There are several effective folk remedies, but it should be noted that they can only help in the initial stage of the disease and subject to the correct preparation proportions:
- Against oidium, you can use an infusion of mullein or rotted hay. The recipe is easy to remember because the number three is always present. Pour one kilogram of raw material with three liters of water at room temperature. Let it sit for three days. Then strain through a thick sieve. This is necessary to ensure that the sprayer does not become clogged. And dilute with water three times. Let it sit for another three hours and only then can you process the plants.
The most accessible of all methods is to prepare fertilizer from humus in the spring of concentrated saprophytic microflora.
- Potassium permanganate solution. You need to take a level teaspoon of the product (5 grams) and dissolve it in 10 liters of water.
- Soda ash solution. Dissolve a heaping tablespoon of the product (30–40 g) in 10 liters of water.
- Garlic extract. Grind 150 grams of garlic and stir in a bucket of water. Strain and immediately spray the plants. The treatment should be repeated no later than after 5 days.
- Ash solution. Take a kilogram of ash and pour it into a bucket of warm water (10 liters). Let it sit for at least 5 days. But at this time you need to stir the solution regularly. Before processing, strain several times and can be used. Sunflower ash will help best. But you can also use wood.
It is imperative to add an “adhesive” to any solution. This can be crushed laundry soap or sugar.
Treatment of grapes with chemicals
To protect and fight fungal infection of grape crops, it is recommended to use chemical compounds that contain sulfur:
- "Cumulus DF";
- "Tiovit Jet";
- colloidal sulfur.
A solution of colloidal sulfur helps get rid of oidium.
The latter is the safest and most effective composition for combating the primary symptoms of the disease on the bush. The result of the treatment can be seen after 3 days.
It is advisable to carry out the procedure on a cloudy day, evening or morning. This is required so that the bunches cannot get burned under the influence of the sun's rays. The temperature should be no higher than +30 ℃ and lower than +20 ℃, because this evaporation method will only bring positive results in warm weather.
A vineyard treated with colloidal sulfur will be protected for 14 days. Since this contact agent can be easily washed off, shrubs must be treated every 14 days or immediately after precipitation.
To prepare a working solution of colloidal sulfur, you should follow these step-by-step steps:
- Pour 30-40 g of the substance into a glass container.
- Slowly pour 10 liters of liquid into a jar, stirring the mixture until smooth, so that a mushy consistency emerges.
- Pour the concentrated mixture into a bucket and mix again.
- Filter the prepared product and pour it into a spray bottle, spraying it over the bunches and green mass.
Prevention
Oidium previously affected only the vineyards of the southern part of the country, but with global warming its range has expanded closer to the central regions. Therefore, you should be prepared to be affected by fungus on grape bushes. To prevent this from happening, it is necessary to carry out preventive measures and prevent the reproduction and spread of oidium. Because the disease will not only reduce the grape yield, worsen the presentation of the bunches, but also weaken the bushes. And those can simply die during winter frosts. This cannot be allowed. After all, it is always better to prevent a disease than to fight it later using your moral and material resources. There are simple preventive works that need to be carried out annually in vineyards:
- In the fall, treat the bushes and soil near the grapes with 3% Bordeaux mixture. Before this, collect and burn the leaves;
- In the spring, before the buds open, spray again with the same solution;
- Before use, it is better to disinfect gardening tools in the same copper sulfate and lime;
- When the first leaves appear, treat the bushes with sulfur powder. Moreover, this must be done very carefully, without missing a single leaf. In addition, spraying the drug not only on the upper, but also on the lower part of the leaf blade;
- The bushes must be constantly thinned out so that they are well ventilated. This can be achieved through fragments and minting. Read about spring pruning of grapes in this material.
In the most vulnerable phases of grape development - “before and after flowering”, “small pea”, “berry growth” - it is necessary to use highly effective systemic and systemic-contact fungicides to protect against oidium.
Which varieties are most susceptible?
There is not a single grape variety that can withstand oidium. Fungal infection depends not only on the climatic zone where shrubs grow and the weather conditions of a particular area in different years. The technological conditions for growing the crop also affect resistance against disease. There are three groups of grapes according to conditional resistance against oidium:
- Sustainable: Muscat Tairovsky, Firstborn of Magarach, Lydia, Muscat Odessa, Kosorotovsky, Ialovenisky canteen, Kishmish Zaporozhye, Bogotyanovsky, Flora, Anthony the Great, Eurostandard, Nadezhda AZOS, Arched and others.
- Medium sustainability: Aligote, Bianca, Augusta, Riesling, Queen of the Vineyards, Merlot, Codryanka, Delight and others.
- Most susceptible to the disease: Zorka, Italy, Caraburnu, Pobeda, Cardinal, Kishmish white and pink, Bastardo, Strashenisky, Atilla, Russian early, Lyana, Favorite, Fairy, Delight, Moldova, Chaush, Doina, Hamburg Muscat, White Chaslas, Pearl Saba , Muscat Kuban, In Memory of Negrul and other varieties.
The most oidium-resistant interspecific hybrids.
conclusions
When vineyards are affected by oidium, the yield is significantly reduced and the berries lose their marketable appearance. In addition, the infected vine does not ripen well, which can lead to the death of the bush. To prevent this, winegrowers use agrotechnical methods aimed at combating oidium:
- Vineyards must be planted in sunny and ventilated areas.
- The bush should not be allowed to become dense. This can be avoided by chipping and chasing.
- Carry out preventive operations in a timely manner in the form of autumn and spring treatment of bushes with Bordeaux mixture.
- If the first symptoms of the disease are visible, the vineyards should be treated with sulfur or fungicides. Folk remedies are also acceptable. But only if the damage to the bushes is not massive.
Timing and schemes for processing the vineyard
Oidium on grapes (photos and descriptions of the disease will tell you how and when to treat the crop) can quickly infect all areas of the bush, causing a decrease in yield and the eventual death of the vineyard. To eliminate the problem, it is necessary to process the crop in a timely manner.
in spring
In the spring season, before the buds swell, with the primary symptoms of infection, treatment of the bush should begin with a 5% lime-sulfur decoction or ground sulfur. It is recommended to pollinate the latter in the morning or at a temperature of no more than +13 °C. This will speed up the process of death of disputes.
The procedure must be repeated after 15 days if 1 treatment was not enough. For spring spraying, folk formulations are suitable, and if the vineyard is excessively affected by powdery mildew, you will need to switch to fungicides.
In summer
It is permissible to use fungicides 30 days before the start of harvesting. During the season, the number of some drugs can be used up to 6 times with the frequency of plant treatment every 15 days. This indicates that spraying can be done in the spring season and continued throughout the summer stage.
in autumn
The autumn season is the time of harvest, so during this period the use of chemicals will need to be minimized and applied to the bush if necessary. If no oidium factors are detected in a given period of time, crop processing can be postponed to a later date after complete harvesting.
Covering plant varieties will need to be treated after sap flow has completely stopped. Non-covering varieties can be left untouched until spring, unless oidium has been detected.
