Most grape diseases can destroy the crop or significantly reduce the quality characteristics of the berries. For this reason, fighting them is extremely important. Among the diseases, mildew of grapes is the most widespread. The treatment of this disease is carried out in accordance with the method of combating fungal infections of plants.
Plant disease is the result of an infection. The reason for the development of pathogenic microbes may be the transmission (infection) of microorganisms from a sick plant to a he althy plant. Also, the development of diseases is influenced by climate, soil characteristics and other conditions for the growth of plant culture. Microorganisms-pests can develop in the soil, on damaged areas of the 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 of mildew
Special dangerfungal diseases is the rapid spread of infection. They are able to cause significant damage to the plant in a few weeks and dry the grape bushes within 1-2 seasons. The rate of spread of the disease depends on the type of infection and weather conditions. For example, mildew (downy mildew fungus) actively spreads in rainy weather, while oidium (vine uncinula mushroom) completely stops development during rain.
Disease countermeasures should take into account the prevalence of infections in the growing area. In the middle and southern strip of Russia, mildew grapes are most often sick. Treatment for a fungal infection is as follows:
- preventive measures - spraying with antifungal drugs, pruning of unwanted shoots, tying up the vine, 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 is powdery mildew, the causative agent of which is the Plasmopara Viticol fungus. This type of disease poses the greatest danger to European grape varieties. The parasitic microorganism infects all the greenery of the vine: foliage, vegetative organs, inflorescences and fruits.
Attacking inflorescences and berries, the fungus completely destroys the crop. Deciduous cover of vine bushesunder the influence of the fungus, it dries up, after which it falls off. A sharp reduction in the area of the deciduous surface disrupts the process of proper ripening of the fruit. The berries of diseased bushes lose their nutritional value and sweetness, the wine made from them tastes sour. A diseased vine ripens poorly, this negatively affects the bush's resistance to winter cold.
The fungus, affecting the plant, develops especially actively on young inflorescences from individual pedicels or ridges. The areas affected by the disease turn brown, all ovaries with inflorescences below die. Under the influence of rain, the fungus actively spreads and destroys the plant.
Mildew distribution conditions
Fungal infection overwinters as spores on fallen vine leaves and soil. In the spring, when the soil becomes very wet, and the air temperature stays at 10 degrees for 7-8 days, 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, description of the disease and its prevention will be considered further.
Description of mildew
Visually, the development of the disease begins with small yellow spots, covering the entire leaf area over time. A sign of the spread of the disease is the appearance of a white fluff inthe bottom of a leaf that forms 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 poses the greatest danger to young inflorescences, since sporulation of the fungus is formed on their surface. Young inflorescences die under the influence of mildew - the berries turn black, wrinkle and crumble. The spread of the disease stops in dry, hot weather, air temperatures above 30 degrees.
General rules for disease control
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 start of flowering and the appearance of small berries (the size of a match head). Consider the methods of combating the disease in more detail.
Mildew countermeasures
The main stage of the organization of the fight is to provide conditions that prevent the development of the disease. The infection that contributes to the development of mildew lives in places of high humidity, in lowlands, which for a long time retain rain puddles, dew and fog. A complex of agrotechnical works contributes to better ventilation of plants and eliminates the accumulation of excess moisture near the grape bushes.
As mentioned, mildew spores overwinter in fallen grape leaves. In the autumn, after the end of the harvest,fallen leaves must be burned.
Spraying vine bushes with poisons that destroy fungi is the most effective way to preserve the harvest. As a rule, they are made with a 1% solution of Bordeaux mixture. For the first spraying, a solution of 0.5% is used, subsequent treatment is carried out with an increase in concentration from 0.75% to 2%. The low content of the active substance prevents the antifungal solution from burning leaves and shoots infected with grape mildew. Treatment (the photo below shows the process) involves spraying the vines with a tank mixture in order to prevent infection.
Anti-fungal mixtures for spraying grapes
There are various folk methods and preparations to combat grape mildew. Treatment with folk remedies is effective as a preventive measure. 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 Bordeaux spray solution.
Mixes containing various components for spraying plants are called tank mixes. Tank mixtures for the treatment of grapes from mildew contain the active substance - copper sulphate. A mixture of Bordeaux liquid consists of a suspension of slaked lime in lime water and copper sulfate.
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 can burnsurface of grape leaves. The main active component of the Bordeaux liquid is characterized by rapid dissolution in water, so rains quickly remove the medicinal mixture from the surfaces of the grape bush.
In order for the solution of copper sulfate to remain on the surface of the plant for as long as possible, it must be mixed not with water, but with milk of lime. Lime neutralizes the acid reaction of copper sulfate, the liquid becomes viscous and sticky. Adhering to the leaves of grapes, the substance stays on the surface longer under the influence of rains.
In order to effectively fight grape mildew, treatment should be carried out with a product that is prepared according to technological standards. The quality characteristics of all components matter.
Paying attention to the main active ingredient - copper sulfate, you should make sure that the powder does not contain foreign impurities, and its color is bright blue. Lime for the solution is suitable for both slaked and quicklime. However, it is better to perform quenching during the preparation of the solution. It is freshly slaked lime that ensures the best adhesion of the drug to the surface of grape leaves.
Proportions of Bordeaux mixture solution
All preparations for the treatment of mildew in grapes have a specified safe concentration of the active ingredient. The concentration of copper sulphate in a solution of Bordeaux mixture can be from 0.5% to 3%, a higher content of the active substance will burn the leaves. To prepare 10 liters of a preparation with a concentration1% 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 whose material 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 dissolves, another 5 liters of cold water are poured into the container. Separately, 100 g of prepared lime is quenched, after which the rest of the water is added and the volume of the lime mortar is adjusted to 5 liters. The lime preparation is filtered. A solution of copper sulphate is gradually added to the resulting 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 the fight against mildew, the active components will precipitate.
Characteristics of a properly prepared preparation
A solution of Bordeaux liquid, which is prepared in accordance with the technology, has a blue color and a mucous structure, sticks to the fingers. Color can signal the concentration of the active substance. For example, green indicates that copper sulfate is added in excess, and if sprayed, the liquid will burn the grape leaves.
Sick mildew grapes? Treatment: how to carry outBordeaux mixture treatment?
It should be remembered that only a freshly prepared solution is suitable for processing grapes. During storage, Bordeaux liquid loses its beneficial properties and becomes neutral for parasitic fungi.
If, upon visual inspection, it is established that grapes are sick with mildew, treatment with a Bordeaux mixture solution is the best solution. To ensure the safety of the prepared product, a metal nail is briefly immersed in it. If the nail is not covered with plaque when the nail is removed, the solution is safe for plants. The appearance of small grains on the surface of the nail will indicate the low quality of Bordeaux liquid and the high content of the active ingredient. In this case, it should be further diluted with lime mortar.
However, the Bordeaux mixture, prepared in accordance with the technology, is also capable of harming the grapes if spraying is performed on a hot day after heavy rain. To minimize the risk of plant scorching, spraying is done at dawn or at sunset.
Prevention of viral and fungal diseases of grapes
The maximum effect is given by measures to prevent fungal and viral diseases. Prevention is carried out during the period of three seasons: spring, summer and autumn. During this time, growers water the bushes, cut the vines and strengthen the agricultural background by fertilizing the soil.
Before spraying the grapes, it is necessary to remove damaged leaves,trim excess shoots and tie up the vine. Garbage in the form of diseased foliage and shoots must be burned to prevent the development of infection.
Caring for grapes before harvest
It is extremely important to carry out mildew treatment on grapes in July. In summer, before harvesting, plant growers perform the main spraying of bushes. The schedule for processing with a Bordeaux mixture solution is every 3 weeks, starting from the first days of July. Spraying of grapes with antifungal drugs is completed in the first decade of August and is not carried out until the vines are pruned.
