Most grape diseases can destroy the crop or significantly reduce the quality characteristics of the berries. For this reason, the fight against them is extremely important. Among the diseases, mildew of grapes is most common. The treatment of this disease is carried out in accordance with the methodology of the fight against fungal infections of plants.
Plant disease is a consequence of infection. The cause of the development of pathogenic microbes may be the transmission (infection) to a healthy plant of microorganisms from the patient. Also, the development of diseases is affected by the climate, soil characteristics and other conditions for the growth of plant crops. Pest microorganisms can develop in the soil, in damaged areas of a plant, or under the influence of adverse weather conditions. The most dangerous for the grape family are parasitic fungal microorganisms. Fungal
plant diseases are caused by phytopathogenic parasites.
We protect grapes: diseases and treatment with mildew
A particular danger of fungal diseases is the rapid spread of infection. They can cause significant damage to the plant in a few weeks and dry the bushes of grapes within 1-2 seasons. The rate of spread of the disease depends on the type of infection and weather conditions. For example, mildew (powdery mildew fungus) actively spreads in rainy weather, while oidium (fungus unzipped grapes) completely stops development during rain.
Disease control measures should take into account the prevalence of infections in the growing area. In the middle and southern strip of Russia, grapes are most often sick with mildew. The treatment for a fungal infection is as follows:
- preventive measures - spraying with antifungal drugs, pruning unnecessary shoots, grapevine garter, removing diseased leaves and branches, removing weeds, etc .;
- maintaining and strengthening the agricultural background;
- preventing the spread of diseased plants and fruits - quarantine.
Mildew is the most dangerous fungal disease
Mildew - powdery mildew, the causative agent of which is the fungus of the plasmopar vitikol. This type of disease poses the greatest danger to European grape varieties. The parasitic microorganism affects all the greenery of the vine: deciduous cover, vegetative organs, inflorescences and fruits.
Affecting inflorescences and berries, the fungus completely destroys the crop. The deciduous cover of the vine bushes dries under the influence of the fungus, after which it falls. A sharp reduction in the area of deciduous surface disrupts the process of proper ripening of fruits. The berries of diseased bushes lose their nutritional value and sweetness, the wine made from them tastes sour. The diseased vine matures poorly, this negatively affects the bush's resistance to winter cold.
The fungus, affecting the plant, is especially actively developing on young inflorescences from individual pedicels or ridges. Affected areas turn brown, all the ovaries with inflorescences located below die. Under the influence of rain, the fungus actively spreads and destroys the plant.
Mildew Distribution Terms
Fungal infection hibernates in the form of spores on fallen grape leaves and soil. In the spring, when the soil becomes very wet, and the air temperature holds at 7-8 days at 10 degrees, the fungus spores swell and germinate.
When they are in a humid environment or rain puddles, they begin to grow actively. In the process, they form a living environment for the formation of zoospores (zoosporangia). After the zoospores are formed, they are carried by the wind to the bushes, and the fungus begins to parasitize, infecting the grapes with mildew. Treatment, a description of the disease and its prevention are discussed below.
Description mildew
Visually, the development of the disease begins with small yellow spots, over time covering the entire area of the leaf. A sign of the spread of the disease is the appearance of a white gun in the lower part of the leaf formed after rain. Infected leaves turn completely yellow and die. You can recognize mildew on the vine by spots that look like small dots of a brownish hue.
The microorganism presents the greatest danger to young inflorescences, since sporulation of the fungus forms on their surface. Young inflorescences die under the influence of mildew - the berries turn black, wrinkle and crumble. The spread of the disease stops when dry, hot weather, air temperature above 30 degrees.
General rules for controlling the disease
If grapes are infected with mildew, treatment is carried out by spraying with a pesticide that destroys the primary foci of infection. Before the grapes begin to bloom, the bushes are sprayed with antifungal mixtures. The next stage of spraying begins immediately after the beginning of flowering and the appearance of small berries (the size of a match head). Consider methods of combating the disease in more detail.
Methods of counteracting mildew
The main stage of the organization of the struggle is to ensure conditions that impede the development of the disease. Infection that promotes the development of mildew lives in places of high humidity, in lowlands, which for a long time delay rain puddles, dew and fog. A set of agrotechnical works contributes to better ventilation of plants and eliminates the accumulation of excess moisture near grape bushes.
As has been said, spores mildew winter in fallen grape leaves. In the fall, after harvesting, the fallen leaves must be burned.
Spraying grape bushes with poisons that destroy fungi is the most effective way to preserve the crop. As a rule, they are produced with a 1% solution of Bordeaux fluid. For the first spraying, a solution of 0.5% is used, subsequent processing is performed with increasing concentration from 0.75% to 2%. The low content of the active substance prevents the antifungal solution from burning leaves and shoots infected with mildew of grapes. Treatment (the photo below shows the process) involves spraying grape bushes with a tank mixture in order to prevent infection.
Antifungal mixtures for spraying grapes
There are various folk methods and drugs to combat mildew of grapes. Treatment with folk remedies is effective as a prophylaxis. An effective method of treatment is spraying with solutions containing active chemical components. Antifungal solutions contain zinc and copper sulfate. The most affordable and effective drug is a solution of Bordeaux spray liquid.
Mixtures containing various components for spraying plants are called tank. Tank mixtures for the treatment of mildew grapes contain the active substance - copper sulfate. A mixture of Bordeaux liquid consists of a suspension of slaked lime in lime water and copper sulphate.
Characteristics of the active component of the Bordeaux mixture
It should be remembered that a solution in a concentration of more than 3% copper sulfate is able to burn the surface of grape leaves. The main active component of Bordeaux liquid is characterized by rapid dissolution in water, so rains in a short time remove the healing mixture from the surfaces of the grape bush.
To keep the solution of copper sulfate as long as possible on the surface of the plant, it must be mixed not with water, but with milk of lime. Lime neutralizes the acidic reaction of copper sulfate, the liquid becomes viscous and sticky. Adhering to the
leaves of grapes, the substance lasts longer on the surface under the influence of rain.
In order to effectively combat the grape mildew, treatment should be carried out with a product that is prepared according to technological standards. The quality characteristics of all components are important.
Paying attention to the main active ingredient - copper sulfate, you should make sure that the powder does not contain any impurities, and its color is bright blue. Slaked lime is suitable for both slaked and quicklime. However, it is better to extinguish during the preparation of the solution. It is freshly slaked lime that provides the best adhesion of the drug to the surface of grape leaves.
The proportions of the solution Bordeaux mixture
All preparations for the treatment of mildew in grapes have a predetermined safe concentration of the active component. The concentration of copper sulfate in a solution of Bordeaux mixture can be from 0.5% to 3%, a higher content of active substance will burn the leaves. To prepare 10 liters of the drug with a concentration of 1% of the active substance, you should take 100 g of quicklime and the same amount of copper sulfate. Mixing is carried out in a container, the material of which is resistant to chemical reactions and does not interact with the components of the solution. The best option is a glass or ceramic container, the use of galvanized or metal containers is unacceptable.
To prepare the mixture, copper sulfate is diluted with one liter of hot water. As soon as the powder has dissolved, another 5 liters of cold water is poured into the container. Separately, the quenching of 100 g of prepared lime is performed, after which the rest of the water is added and the volume of the lime solution is adjusted to 5 liters. The drug is filtered lime. A solution of copper sulfate is gradually added to the obtained milk of lime. The process of combining the components is accompanied by constant stirring.
It should be noted that a solution of copper sulfate is added to the lime solution, and not vice versa. With an incorrect sequence of actions, the resulting suspension will be ineffective in combating mildew, the active components will precipitate.
Characteristics of a properly prepared drug
The Bordeaux fluid solution, which is prepared in accordance with the technology, has a blue color and mucous structure, sticks to the fingers. Color may indicate the concentration of the active substance. For example, green indicates that copper sulfate is added in excess, and when sprayed, the liquid will burn the grape leaves.
Sick grapes mildew? Treatment: how to treat Bordeaux mixture?
It should be remembered that only freshly prepared solution is suitable for processing grapes. Bordeaux liquid during storage loses its beneficial properties and becomes neutral for parasitic fungi.
If a visual examination found that grapes are sick with mildew, treatment with a solution of Bordeaux mixture is the best solution. To ensure the safety of the prepared product, a metal nail is immersed in it for a short time. If when removing the nail it is not covered with a coating, the solution is safe for plants. The appearance of small grains on the surface of the nail will indicate a low quality Bordeaux fluid and a high content of the active component. In this case, it should be further diluted with a lime solution.
However, Bordeaux mixture prepared in accordance with the technology is also capable of harming the grapes, if spraying is carried out on a hot day after heavy rain. In order to minimize the risk of burns in plants, the treatment is carried out at dawn or during sunset.
Prevention of viral and fungal diseases of grapes
The maximum effect is given by measures for the prevention of fungal and viral diseases. Prevention is carried out during the three seasons: spring, summer and autumn. During this time, plant growers water the bushes, cut the vine and strengthen the agricultural background, fertilizing the soil.
Before spraying the grapes, it is necessary to remove the damaged leaves, trim the excess shoots and tie up the vine. Garbage in the form of foliage and shoots affected by the disease is necessarily burned, preventing the development of infection.
Grape Care Before Harvesting
It is extremely important to perform mildew treatment on grapes in July. In the summer, before harvesting, the main spraying of bushes is carried out by plant growers. The treatment schedule with a solution of Bordeaux mixture - every 3 weeks, starting from the first of July. Spraying grapes with antifungal drugs ends in the first ten days of August and is not conducted until the vines are pruned.