In a short time, an entire vineyard can die from anthracnose on the grapes. Previously, winegrowers in the southern regions, where the climate was humid and warm, had to deal with this scourge. The problem is now increasingly encountered in temperate regions. Hybrids (varieties) with high resistance to oidium and mildew are prone to the disease.
Signs of anthracnose
In its advanced form, anthracnose grape disease affects the entire plant. Constant monitoring is necessary to avoid crop loss. Young leaves are the first to suffer.Small dark dots form on their surface. They quickly increase in size, turning into spots.
The color of the new growths on the leaves is brown, the edges are darker. Because of these spots, the disease is popularly called spotted anthracnose. The affected surface can cover the entire area of the leaf blade; its color becomes dirty pink over time.
Diseased leaves eventually dry out and fall off, the infection spreads further and spreads to the shoots. Brown spots appear on them, which grow wider and deeper, becoming dark brown. Cracks appear at the affected areas. If the days are dry and hot, the diseased shoots dry out and break. In rainy weather they begin to rot.
On berries, the infection manifests itself as round, concave spots. Their main color is brown, only the central part is purple. Sick berries dry out and fall off. Anthracnose on the racemes can be seen before the flowers bloom. Spots appear on them, the same as on the shoots. The part of the brush located below the spot dies. The one that is higher continues to develop, but does not produce a harvest, since the ovary falls off over time.
Causes of the disease
The causative agent of anthracnose is a fungus of several species: Kabatiella, Gloeoporium, Colletotrichum. All its varieties are very tenacious, they are not afraid of cold weather, the spores overwinter on plant debris and on diseased vines.
A fungal infection may not manifest itself for years, but its onset can be triggered by:
- improper pruning;
- mechanical injuries to shoots;
- bad weather (rain, hail);
- the soil is acidic, saline;
- lack of phosphorus and potassium in the soil.
Favorable environment for active growth of fungus — increased air and soil humidity and temperature conditions from 23 to 35 °C.
How to fight and how to treat
Only systemic control of infection guarantees the salvation of the vineyard from anthracnose. You should not give up when symptoms of the disease appear. You can cope with the fungus. You just need to know how to treat a diseased vine. Symptoms of anthracnose appear in the spring; treatment must be done immediately; all measures must be carried out before mid-summer.
Agrotechnical measures
Agrotechnical measures are the first method of treating anthracnose. It is especially effective if the vineyard area is small, each vine can be treated:
- cut out diseased hands;
- cut off the leaves;
- Cut off shoots with traces of the disease, grabbing up to 4 cm of a healthy area.
All trimmings should be poured into a polyethylene bag; they should not be thrown on the ground, as this may lead to further spread of the fungus. After completion of sanitary work, all plant debris must be burned.
To reduce fungal activity, reduce watering. As a result, the top layer of soil (1 cm) becomes dry. The row spacing is cleared of weeds, which also reduces humidity in the root zone. The final stage is feeding. To increase immunity, phosphorus-potassium fertilizers are applied.
Drugs
Now there are no problems with purchasing effective drugs against fungus. Grape growers prefer biological means. They work well against fungus, do not harm the environment (insects, soil), and are safe for humans and pets.
Popular drugs against anthracnose:
- "Plantrees";
- "Gapsin";
- "Mikosan."
The drugs from this list have been tested in practice by many winegrowers. No effect on the quality of the crop (taste, composition) was noticed. A positive effect on the formation and growth of shoots was noted. After treatment, the plants quickly restore the volume of green mass.Treatment with these drugs is carried out every 2 weeks.
Fungicides
For advanced forms of the disease, systemic fungicides against anthracnose are used. According to reviews, good results are achieved with the use of Ridomil, Fundazol, and Acrobat. You can treat vineyards with other preparations:
- Bordeaux mixture;
- "Fitosporin M";
- "Trichodermin";
- "DNOC."
The vineyard is treated in the spring, when the shoots have just begun to grow and do not exceed 10 cm. Treatments with a fungicide solution are carried out only in the evening and morning. This avoids sunburn of the leaves.
Traditional methods
Any experienced winegrower will say that treatment with folk remedies will not give positive results if signs of anthracnose appear on the leaves, shoots, and brushes. Spraying bushes with soda, kefir, potassium permanganate and other similar means is pointless.
There is no need to be afraid of chemistry, only modern drugs will help cope with the harmful fungus. Biological preparations, systemic fungicides and agrotechnical measures are the only correct ways to combat anthracnose.
Prevention
A well-groomed vineyard is less likely to suffer from anthracnose. Basic preventive measures: timely and correctly carried out sanitary and formative pruning (spring, autumn), in the summer - pinching. A neglected, thickened vine more often suffers from fungus.
All work in the vineyard is carried out with clean tools treated in a solution of potassium permanganate. Leaves and shoots can also be sprayed with the same composition before treatment. In spring, prevention is carried out in several stages:
- the first stage before flowering is spraying with Bordeaux mixture (1%);
- the second stage two weeks later with a solution of copper oxychloride.
Sulfur powder protects well against anthracnose. For prevention, they pollinate the vineyard in the spring. After summer thunderstorms and heavy rains, the bushes are sprayed with fungicide or Bordeaux mixture.
Autumn preventative work:
- application of fertilizers (potassium, phosphorus);
- sanitary pruning of diseased, damaged shoots, their destruction;
- raking and destroying all leaves;
- processing of row spacing (loosening);
- covering the soil with mulch.
Most commonly affected varieties
A variety resistant to mildew may be more likely to suffer from anthracnose. Experienced winegrowers have found that the varieties most susceptible to the disease are:
- Husayn;
- Isabel;
- Karaburn;
- Lydia.
Of the old selection varieties, the following are relatively stable: Riesling, Chassela Belaya, Saperavi, Cabernet-Sauvignon, Nimrang, and the hybrid form Viorica. Modern selection does not stand still. New varieties and hybrid forms of grapes are appearing, the resistance of which to anthracnose is not yet available in the scientific literature.
The choice of grape variety (hybrid) affects the health of the vineyard, but in practice, resistance to the fungus does not always correspond to that declared by the breeders. Only basic knowledge of vine care and preventive measures will help preserve the harvest.
