White bloom on bunches of grapes how to fight. Gray mold on grapes
Grapes are one of the most refined and capricious horticultural crops. It is affected by a number of fungal, bacterial and viral diseases that are difficult to treat. With untimely action, you can completely lose the vineyard. Very common on leaves and fruits white coating, which can signal various diseases of the plant. Let's try to figure out why a white bloom appears on the grapes. How to treat damaged bushes.
downy mildew
The second name for this common fungal disease of grapes is. Where there is a vineyard that is not well treated, including for preventive purposes, sooner or later mildew is diagnosed. The fungus settles on healthy tissues, forming a white coating. It is not easy to get rid of this misfortune, since the spores successfully endure the winter on fallen leaves and in the soil, and with the first warmth they begin active life. During the growing season, the mildew fungus can reproduce up to 20 generations of spores.
Outwardly, the manifestation of downy mildew is expressed in the appearance of white spots. In conditions of high humidity, they appear on the leaves. During the heat, spores slow down their activity, waiting for the most favorable period. Effective control of downy mildew requires mandatory preventive measures. The following preparations are suitable for processing: Antrakol, Khorul, Bordeaux Liquid, Kuproksat, Thanos. The first treatment of the vineyard should be carried out when the length of young shoots reaches 15-20 cm. The second treatment is carried out before flowering, the third - during the formation of the ovary.
powdery mildew
If downy mildew provokes a white coating on the leaves of grapes, then genuine powdery mildew is a white coating also on the fruits. The second name of this fungal disease is. You can diagnose the disease at the beginning of the growing season. On the bushes there are shoots that are very stunted with twisted leaves and partially or completely covered with whitish dust. Since June, a white coating appears on the inner surface of the leaves, and then on the outer. Affected inflorescences and clusters outwardly look like they are sprinkled with flour.
When the crop ripens, the fruits burst and begin to rot. The berries become soft and have a putrefactive taste, they are not suitable for food. If you do not take action, then you can lose not only the entire crop, but also lose the vineyard itself. Moreover, the spread of the disease is carried out from affected plants to healthy ones.
The optimal environment for the spread of oidium is warm and humid weather. The appearance of white plaque is only the initial stage of the progression of the disease. Subsequently, the entire vegetative (green) mass will darken and die, all this will lead to the complete death of the shrub.
When the first signs of the disease are detected, treatment should be carried out. For these purposes, drugs are optimally suited: "Strobe", "Thiovit", "Topaz", "Horus", "Thanos". Spraying is repeated three times with an interval of 10 days.
The main preventive measure to combat grape oidium is proper agricultural technology. Bushes should be well ventilated, for this you need to tie up shoots, remove stepchildren and remove weeds.
Alternariosis
This is another dangerous fungal disease, which in last years gaining more and more popularity, the second name is olive blotch. This fungal disease that affects fruits and leaves looks like oidium. After infection, on the 10-14th day, a silvery coating and mold can be seen on the leaves. If measures are not taken and white bloom covered the clusters, this is evidence that the crop has been ruined and the vine must be saved from death. Biological preparations, for example, "Trichodermin", are effective for the prevention of alternariosis. In the spring, treatment can be carried out as a protection. During the formation of the ovary, systemic fungicides are used: "Ridomil", "Kvadris", "Skor", "Rapid".
Prevention of fungal diseases of grapes
As mentioned earlier, prevention measures play a key role in the fight against fungal diseases in the vineyard.
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Among the diseases of a fungal nature, one of the most dangerous and widespread is the black spot of grapes (Phomopsis viticola Sacc.). The defeat of her is complex and covers all parts of the plant. This infection owes its speaking name to its specific symptoms: when infected, black blotches appear on the shoots and leaves of the grape bush. What to do if trouble came to the garden and the disease struck the plants? Is there an effective drug that allows you to get rid of the black spot found on the leaves and shoots of grapes?
History of the spread of the disease
The historical homeland of the disease is America. It was first identified and described by D. Rerik back in 1909. The spread of infection in European territories occurred in the second half of the 19th century, after its pathogen was brought there along with grape seedlings. When the vineyards were transferred to the standard culture, mass cases of disease damage appeared.
To date, the geography of the spread of infection is extremely extensive, it can be found in all areas of grape cultivation: in Moldova, Ukraine, Russia, in the North Caucasian lands and outside the Caucasus.
The disease has many other names, including
- death of shoots;
- cracking of the bark;
- dry arm;
- phomopsis.
The pathogenic reaction is caused by the imperfect fungus Phomopsis viticola. The most favorable for its development are cool climatic conditions with high humidity.
Signs of the disease
When grapes are infected with black spot, discolored areas appear on the bark of shoots that have had time to lignify in the first year of life and stems covered with perennial wood. At the initial stage of the development of the disease, such spots can be found in the area of the first 6-7 internodes. If the disease progresses, they move to other parts of the bush: fruitful links, sleeves, stems.
Under favorable temperature conditions (above 10˚C), in areas that have lost color, the formation of fruiting bodies of the fungus, pycnidia, which outwardly look like numerous black blotches, occurs. The penetration of mycelium deep into the bark leads to its decay, which significantly weakens the development of the entire plant, and in the future can cause the death of its individual arms.
On the green parts of the grape bush, the infection begins to appear in June. First of all, its signs are found on young annual plants, which are covered with small black-brown specks of a round or oval shape. With the growth of shoots, they also increase in size, often merging into oblong spots. The vine cracks, acquiring a light brown color from the inside. In this case, the edges of the affected area harden, resembling appearance scabs.
Gradually, signs of infection appear on the leaves of the plant. To a lesser extent, they are found on tendrils, ridges of grapes, flower caps, and berries.
On the leaves, necroses are formed, surrounded by a clarified tissue of a denser structure, having an oval or angular shape. Basically, they can be seen next to a powerful vein, which completely blackens. Due to the fact that the fabric of the sheet is stretched, it is deformed, often even torn. Heavily damaged foliage turns yellow and flies prematurely.
Mechanism of infection
In the spring, when the air warms up to a temperature of more than 8˚C and there is a water film, pycnidia release spores from themselves. Their distribution occurs with drops of water (in the rain, with heavy dew), they are also carried by gusts of wind and various insects. Once on the green areas of the plant, spores germinate. This process is possible if the temperature is 15-35˚C and the relative humidity is at least 85%.
Consequences of infection
If measures are not taken in a timely manner to combat this dangerous infection, more and more large areas will be affected by black spot on the grapes. After 5-6 years, a progressive disease will lead to the death of the plant. Due to the deep damage by the disease to the parts of the bush responsible for vegetation and generation, about half of the crop can be lost.
Due to deformations and ruptures of the leaf plate, photosynthesis is weakened. In the lower internodes of young annual shoots, which are especially strongly affected by fungi, up to 60% of the buds can die. The number of eyes decreases, and the shoots begin to develop in an inconvenient area where they are easily subjected to accidental breaking off - at the top of the fruit arrow. Affected shoots cannot be used to obtain seedlings, which complicates the propagation process.
Infection reduces the resistance of vine bushes to frost, which complicates the wintering of plants.
The greatest danger is the development of black spot during the growing season, especially when the bark of perennial bushes freezes in winter.
Features of some varieties
Some grape varieties have field resistance to infection. Among them:
- Cabernet Sauvignon;
- Taurida;
- Spark;
- Traminer;
- In memory of Verderevsky;
- Bastardo Magarachsky;
- Relay race.
Others require special attention, as the disease affects them greatly, for example:
- Saperavi northern;
- Italy;
- Dove;
- Mattress;
- Aligote;
- Dniester pink;
- Chaush;
- Karaburnu;
- Stepnyak;
Disease control measures
Control measures aimed at the destruction of fungal fruiting bodies and spores are more widely used, but they are not effective enough. For the prevention of the disease, spraying of grape bushes is carried out, using the drug DNOC or Nitrafen. During the growing season, Bordeaux liquid or its analogues (Mikal, Euparen, Efal) are used for these purposes. Such treatments should be started earlier than the fight against mildew and atracnose. As soon as the buds on the shoots swell, the plant is sprayed for the first time. After the appearance of 4-5 leaves, it is time for the second treatment.
When the bushes have faded, the timing of spraying to combat black spot coincides with the protective treatment of plants against downy mildew. During this period, it is permissible to use the same drug (suitable for the treatment of both phomopsis and peronosporosis).
If the lesion is severe, treatment is carried out according to the following scheme. In late autumn, after the grapes have been pruned or when the foliage has fallen from it, the plant is sprayed with copper-containing products, ensuring that the bushes are thoroughly washed. Sleeves with signs of drying are removed.
Black spot is a disease of grapes, whose treatment is quite laborious, therefore, infection prevention is required, in particular, treatment with contact fungicides (Maxim preparation, products containing such active ingredients as folpet, captan, propineb, triadimenol, mancozeb). Such disease control measures reduce the likelihood of primary infection of plants.
Allow to reduce the spread of infection agrotechnical measures to combat black spot.
Necessary:
- timely remove the affected areas of the plant, burning them afterwards;
- for laying young plantations, use only healthy planting material;
- monitor the condition of the bushes, properly form them, providing the plant good development and health;
- tie up shoots, not allowing them to lie on the surface of the soil;
- feed plants with balanced fertilizers;
- provide grape bushes with a sufficient amount of trace elements, especially zinc and boron.
Since black spot has a chronic form, it must be understood that the treatment of infection will be lengthy. It is impossible to completely get rid of the disease, even with numerous and thorough treatments in the autumn and spring, in a short time.
Like any fungus, botrytis prefers heat and high humidity. The pathogen infects weakened plants and, in the form of mycelium, winters well with grapes. If the summer resident is too lazy to remove fallen leaves and berries in the fall, they become a breeding ground for a fungal infection.
With the advent of spring, the mycelium and immobile spores grow and are carried by the wind in May. The rapid reproduction of the infection in the summer can completely ruin the garden, so you need to start fighting the signs of gray rot as soon as possible, using special preparations and folk fungicides.
The following factors increase the likelihood of infection:
- Damp weather;
- dense plantings;
- Inflated indicators of air humidity;
- Poor ventilation due to density and a large number of shoots;
- Cultivation of varieties characterized by a dense cluster and a sugar content index of more than 15%.
Symptoms of gray rot on grapes
The main localization of gray rot is the aerial part of the bush. Let's consider each department in order and describe the specific symptoms of gray rot on grapes.
On the leaves
Brown spots with bloom on the leaves of grapes are a clear sign of gray rot. The plaque consists of conidiophores - fungi that scatter motionless spores. In conditions of heat and high humidity, botrytis is manifested by drying and falling of infected leaves.
On the run
On the branches of the vine, a fungal disease causes necrosis of the woody part. Dead tissue has a brown tint and a gray coating. Rot gives the vine a yellowish color or makes it discolored.
On inflorescences
During the flowering period of grapes, gray rot spoils its buds. Inflorescences change their color, fade and fall off the vine.
On bunches
Fungal gray rot on grapes touches the legs of the ridges and inhibits the development of brushes. Berries quickly wither and dry out.
On fruits
It is easy to distinguish gray rot on grapes by several symptoms:
- The formation of round foci of purple color.
- Darkening of the skin and loosening of its structure.
- Fruit death.
A common symptom of gray rot for different parts of the grape is a gray fluffy coating formed by mitospores of fungal agents. Grape disease got its name precisely on this basis.
How to treat gray mold of grapes
Prevention and treatment of gray rot in grapes is carried out 4 times per season:
- When the plants have bloomed.
- When forming clusters.
- A month and a half before harvest.
- After the fall.
In the absence of natural risk factors for the development of a fungal disease, the grapes are processed twice - before closing in the brush and shortly before cutting the ripe bunches. With a high prevalence of botrytis in the region, leaves and buds are additionally processed before flowering.
Used against botrytis:
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More gentle options would be potassium iodide, diluted with water in a proportion of 2 g of the substance per 10 liters of liquid, and copper sulfate (15 g for each bucket of water). Spraying with Mikal, Antrakol and Folpan will also help protect grapes from gray rot. Some gardeners use a solution of baking soda and manganese crystals.
To rid the plantation of a fungal infection forever, it is important to prevent plants from getting used to drugs. To do this, when processing the garden, alternate spraying solutions.
Gray rot on grapes: how to deal with folk remedies
In order not to treat the fruit crop with chemicals, which, if mishandled, can lead to human poisoning and damage to plantings, we recommend using folk remedies for gray rot of grapes.
Here are a few recipes for an effective fight against botrytis:
- Iodine solution. 10 drops of iodine are diluted in a bucket of water and the plantation is sprayed weekly.
- Garlic infusion. During the day, 100 g of garlic peels are insisted on water heated to 40 ° C. The amount of liquid - 10 liters.
- Mustard infusion. Powder is poured hot water at the rate of 50 g of mustard per 5 liters of liquid. The solution is infused for 2 days and additionally diluted with water in equal proportions.
- A solution of baking soda. To increase the sugar content of the culture, eliminate the mycelium of the botrytis fungus and treat the oidium, the grapes are sprayed with 8 - 10% soda concentrate.
Preventive actions
Prevention of gray rot consists in regular spraying of grapes and a careful examination of weakened areas of plants and places of cuts after green operations. Since botrytis loves an excess of nitrogen fertilizers, this factor must be eliminated.
Experienced agronomists know that the primary infection of grapes with gray rot in the spring does not develop further if the weather is consistently dry in the summer. However, this is no reason to risk the condition of the vineyard and not protect it from the fungus. Neglect of therapeutic and preventive measures is fraught with decay of the ridges and the fruiting part of the vine.
So that shrubs do not grow, it is important to comply with the norms for planting young growth per unit area. With this approach, the nursery will be able to be well ventilated and protected from infection in a natural way.
Proper feeding and watering of grapes, as well as timely pruning, chasing, thinning the ovary, crown formation and spraying of shrubs, are an integral part of the fight against gray rot. The frequency of watering in order to avoid increasing the humidity in the garden should be determined by the stage of development of a particular bush.