Pathogenic microbes often attack plants in the garden. Diseases have different origins. The cause of grape Alternaria blight is saprophytes - fungal microorganisms. In recent years, abnormal heat has led to the spread of the problem in many regions of the country. Therefore, it is important for gardeners to know the symptoms of the appearance and methods of controlling parasites.
Description of the disease
The environment for the proliferation of fungal mold is high air temperature combined with high humidity. Such conditions often occur in regions traditionally suitable for growing grapes.
The causative agent of the disease is dangerous, first of all, to weakened plants. Fungal spores quickly spread throughout the above-ground part of the vine and cause necrosis of leaves and fruits.
How do signs of grape Alternaria blight appear?
Symptoms of grape damage by pathogenic microbes appear in the spring. May thunderstorms and air temperatures above 26 °C create favorable conditions for spore damage. The vine and leaves are covered with a silvery coating and yellowish spots. As the disease progresses, the light spots darken and then turn black. The shoots gradually dry out.
In summer, Alternaria also affects grape fruits. At the same time, the berries wrinkle, acquire a gray tint and lose their taste.
Signs of the disease are often confused by beginning winegrowers with traces of oidium. To ensure the diagnosis is correct, the shoots are placed in a humid environment. Fungal plaque quickly covers the entire branch of the plant.
Methods of treating the disease
Treatment of Alternaria begins immediately to prevent crop loss and death of the grape bush.
Chemicals
To combat fungal diseases, preparations containing copper are chosen. Stages of preparing a product for treating plants:
- Slaked lime is diluted in a separate container and filtered.
- Filter the copper sulfate solution.
- Combine the resulting mixtures.
Grape growers also use other chemicals for spraying. It is recommended to treat a diseased crop according to the following scheme:
| Processing times | Means used |
| During the period of swelling of the buds after gartering the shoots (from March 20 to April 10) | Prevention with copper-containing fungicides |
| After the leaves appear (from April 25 to May 10) | "Trichodermin" |
| Before the fruits ripen (every 2 weeks, starting from the last days of May) | Use one of the drugs: “Rapid”, “Quadris” or “Cabrio-top”, as well as “Skor” |
Spraying times vary depending on weather conditions. And the procedure must be repeated if it rains immediately after processing the grapes.
Folk remedies and recipes
At the early stage of the disease, traditional methods are also effective for treating Alternaria.
Mullein infusion
To prepare the mixture, you need to pour about 3 kilograms of manure into a bucket of water. The resulting composition is left to infuse. After 3 days, the solution is filtered and then the vines are treated.
Manure for spraying is not used fresh, but after a short pause to avoid burning the leaves. The folk remedy for Alternaria blight is popular in small private vineyards, and even in large farms engaged in mass cultivation of the crop.
Potassium permanganate solution
The product is prepared by diluting 5 grams of potassium permanganate in 11 liters of water. Agronomists advise observing the dosage so as not to burn the surface of the leaves. During preparation, focus on the color of the solution. The required concentration gives the liquid a faint pink tint.
The entire grape bush is sprayed with potassium permanganate, not just the affected shoots. Early shoots are watered at the root.
Liquid from milk
Sometimes a mixture of milk and water is used to combat Alternaria. The proportions for preparing the solution are 1 to 10. The composition is poured into the sprayer 30 minutes after stirring. The above-ground part of the grapevine is processed. Heat activates the development of bacteria, which displace fungal spores.
The effectiveness of the method is not very high. This method of treatment is used for early detection of the disease.
Laundry soap with soda ash
Regular laundry soap also copes with Alternaria grape blight. To treat fungus, stir 30 grams of the product in a bucket of water and add the same amount of soda ash. The mixture forms a film on the leaves that inhibits the spread of spores. And the alkaline environment destroys pathogenic bacteria. It is useful to repeat spraying after 10 days.
Prevention of infection
Prevention of grape Alternaria disease involves comprehensive measures:
- Mechanical methods to prevent the disease include regular pruning of infected shoots followed by burning.
- Agronomic methods mean the use of fertilizers and concentrates with microorganisms. Useful substances will strengthen the plant’s immunity and prevent harmful bacteria from developing.
- Chemical prevention involves treating the vines with copper preparations. Experienced winegrowers alternate copper sulfate with a 2% solution of Bordeaux mixture.
Additional measures include the addition of mineral complexes, timely watering and loosening of the soil. Removing weeds from the site will have a beneficial effect on the development and ripening of grapes.
Resistant varieties
Some grape varieties have strong immunity to diseases.Alternaria rarely affects such plants. Gardeners advise growing Rkatsiteli or Traminera. Cabernet Sauvignon and Riesling are resistant to pathogenic microbes. The Amur varieties have proven themselves well - Triumph, Proryv. Marinovsky or Amethyst grapes do not cause problems.
Preventive measures help avoid problems with growing crops. At the first suspicion of Alternaria blight, treatment of the plant should be started immediately. An advanced disease will make it impossible to harvest a good harvest of healthy and tasty berries.
