Grapes are a plant that has been known for several millennia. Delicious aromatic bunches, which are difficult to grow, seem to be filled with the sun and have a huge amount of nutrients. The vine, like any other plant, can get sick. Grape mildew is a serious attack. Having discovered a problem, it is necessary to immediately begin to fight the disease so as not to destroy the entire vineyard.
What is this disease?
Mildew, a fungal infection of grapes, ranks first among the diseases that European vineyards are exposed to. The disease was introduced to Europe in the 19th century from North America along with infected vines of new varieties, and was first discovered in England.
Due to the peculiarities of the European climate, the disease began to spread rapidly, affecting the local vine, destroying the entire crop in a short time. Soon mildew swept across the continent, the vineyards of France and other European countries were infected, dramatically reducing the number of grapes and ruining winemakers.
It causes the infection of the omyocet - a mushroom-like organism, a representative of the Pyronospore family, the disease is also called the downy mildew of grapes.
At first, the green leaves of the grapes are covered with light yellowish-oily spots. In large leaves, yellowness may appear along the veins; under favorable conditions for the fungus (warm, humid weather), the disease begins to progress rapidly. On the back of the leaves, spots, a barely noticeable whitish fluff appears.
If you do not take urgent measures, the shoots dry up, the ovary is quickly affected and the leaves fall off. Of course, in this case, you no longer have to wait for the harvest, the main thing is to get rid of the mildew on the grapes as soon as possible and save the vine.
What is the difference between mildew and oidium?
If mildew is called downy mildew, then oidimum - the second frequent and very dangerous fungal disease of grapes - is simply called powdery mildew.
A white smoky bloom on the leaves (from a distance it seems that the plants are sprinkled with ashes), the affected, bursting, flowing berries, as if dusted with flour, are all symptoms of odium. If the disease is not treated, a thick layer of plaque becomes like felt, cracked berries exude a rotten smell, the grape harvest is significantly reduced, and it is no longer suitable for processing.
Important: mildew appears on the back of the leaves, a whitish fluff forms on the wrong side; oidium affects the outer part of the leaf, covering it with a bloom.
For the treatment of vineyards from odium, preparations containing sulfur are used. The first treatment is carried out in the spring, after removing the shelter, (the vine must first air for several days) the second time the plant is sprayed after harvesting. Azophos is used for processing. Sulfur should get not only on the bushes, the soil under the bushes and around the plant is covered with a fungicide.
If you do not take preventive measures and do not promptly treat the diseases that have arisen, this dangerous "couple" can completely destroy the vineyard in a matter of days. Plants stop growing and bearing fruit, do not tolerate the coming winter and, with a high probability, will get sick next year.
Causes of occurrence
Spores of the dangerous mildew fungus on grapes are resistant to cold weather. They winter safely in fallen leaves. The first spring rain, hitting the soil, raises them, fixing on the lower leaves, and the mildew quickly spreads throughout the plant. If this is accompanied by warm (+ 20-27 ° C) and humid weather, the rapid spread of the disease becomes almost inevitable. After 5-20 days, the first signs of infection are noticeable.
The wind promotes the transfer of the fungus to new areas. If the plants are planted too close together, the disease quickly spreads to the entire vineyard. Heat and humidity reduce the time it takes for mildew to develop; under favorable conditions, the fungus can reproduce up to 8 generations. In dry weather and air temperatures above +30 ° C, the fungus does not survive, therefore it is not typical for Central Asia.
The main symptom and sign of mildew development is the appearance of yellowish oily spots on the face of the leaf. From the inside, it is covered with a whitish fluff, better visible on young foliage. Then the stain grows, becomes reddish-brown, the leaf dries up, curls and falls off, allowing the spores to start a new cycle.
Young shoots and flowers of the plant are especially quickly affected. Berries infected with downy mildew become dark and shriveled, they dry out, crumble, giving the clusters an unattractive appearance. In severe cases, branches are affected.
Young shoots stop growing, the vine, affected by the disease, sheds its leaves prematurely.
Mildew control measures
Grape mildew treatment is carried out with the help of chemicals and folk remedies. Preparations based on copper, lime and sulfur are detrimental to the fungus. Spraying is carried out several times per season, depending on the susceptibility of the variety to this disease.
Important: the fungus gets used to the drugs and develops resistance, therefore, if the vineyard is sprayed more than 3 times per season, it is necessary to diversify the arsenal of means.
The varieties most attractive to the fungus, for example, Kishmish, are processed throughout the growing season, every 2-3 weeks.
Mildew control is a whole range of measures to preserve the crop. In this case, the affected leaves and clusters must be torn off and destroyed (buried or burned) - they cannot be used as compost.
Pruning old vines and disposing of leaves can help prevent disease from developing in the new season. Mulching the land around the plant is also a vineyard protection measure.
An excess of nitrogen in the soil and a lack of potassium can trigger an outbreak of the disease.
Methods and means for processing grapes
Copper-based formulations (copper sulfate, Bordeaux liquid) are effective as a preventive measure. Such treatment was ubiquitous, so today its effectiveness has slightly decreased - the fungi simply developed resistance to drugs.
Mildew treatment of grapes is carried out in several stages.
For the treatment of vineyards affected by the disease, fungicidal agents of complex action are used, which allow you to immediately fight mildew, odium, spider and felt mites. Stages of protective measures:
- The first processing of grapes is carried out in the spring, after the temperature rises to +8 ° C. Landings are treated for prophylactic purposes with a 3% solution of copper sulfate or Bordeaux liquid.
- The next treatment for mildew is performed after the appearance of the first leaves, used: Delan, Horus, Hom.
- In the flowering phase, the plant is treated twice: the first time - before flowering, the second time - after the grapes have faded. Use Delanne, Strobe, and other suitable drugs.
- During the ripening of the berries, when they gain juice and grow intensively, the grapes are not sprayed with fungicides. During this period, to protect the grapes, it is possible to use Baikal and Fitosporin, but it is still better not to use chemicals.
- The last treatment of grapes with drugs is carried out for preventive purposes, after harvest, in August. Processing is carried out with copper or iron sulfate, fungicides can be used.
When choosing how to treat plants, it should be remembered that when using chemicals, working mixtures are prepared in strict accordance with the manufacturer's instructions on the packaging, outdoors or in a well-ventilated area.
All work (solution preparation, spraying) is carried out using protective equipment: glasses, rubber gloves, a protective apron. After processing the plants, you should take a shower.
Not everyone wants to treat their own vineyard with fungicides, especially if there are not very many grapes in their summer cottage. In this case, processing is carried out with folk remedies. At the same time, not only the vine is disinfected, but also the ground under it, because there may be spores of the fungus.
For the purpose of prevention, the soil under the grapes is treated with a decoction of tansy.
300 grams of a fresh plant or 30 grams of a pharmaceutical preparation are poured with 10 liters of water and infused for a day, then boiled for 2 hours, and after cooling down, the soil around the plant is watered with undiluted infusion.
To protect against mildew, the vine is sprayed with an extract of wood ash with the addition of laundry soap. To prepare a working solution, a kilogram of ash is dissolved in a large bucket of water and infused for 1-3 days. The mixture is diluted 1:10, 3 tablespoons of liquid laundry soap must be added to each bucket of the finished solution. This mixture is sprayed into the vineyard.
Another method is spraying the grapes with a potassium permanganate solution. For this, a teaspoon of the product is thoroughly dissolved in 10 liters of water.
In addition, solutions of soda ash or baking soda are often used for processing.
Experienced gardeners spray grapes with an infusion of rotted straw, which is infused for a week - this is one of the oldest folk ways to protect grapes from mildew.
Of course, folk remedies are most effective at the initial stages of infection, and they have to be used much more often than fungicidal preparations, but they can be used without fear of the content of toxic substances in the berries.
Mildew resistant grape varieties
Thanks to the work of breeders, today grape varieties that are resistant to mildew have been obtained, which develop well in the conditions of the Russian climate. Examples of such plants are: Timur, Vostorg, Agat Donskoy, which, moreover, have excellent frost resistance. Monarch is also resistant to mildew, but it is often attacked by powdery mildew.
When planting a vineyard, in order to avoid trouble, you should choose zoned varieties bred taking into account the climate and humidity in a particular area.
What to do for prevention
There are several rules to prevent mildew loss. To prevent the disease, you should:
- do not place plants too often. The distance between planting rows is 3 meters, between adjacent bushes - 1.5-2 meters;
- regularly mulch the soil under the vine;
- use drip irrigation;
- prune grapes, remove fallen leaves and dead old branches;
- after harvesting, before winter shelter, carry out the processing of plants.
Simple recommendations for protection and timely prevention can reduce the risk of developing a disease not only with downy mildew, they will help to resist powdery mildew, other ailments, and protect plantings from pests.
Growing good grapes is not an easy task. Preventive treatment of plants will reduce the likelihood of disease. The vine requires careful careful maintenance, however, if it is possible to do this, when looking at the brushes filled with juice, the mood will surely rise.
And the health benefits of high-quality grape juice or homemade wine are superb.