Prevention and treatment of anthracnose on grapes

Recently, viticulture has become available in many territories of Russia, where previously they did not dream of cultivating vines. But after the culture, in a rather harsh climate, infections traditional for fruit vine, for example, grape anthracnose, adapt. Breeders are breeding varieties that are resistant to natural conditions, but there is no vines immune to the disease yet.

Causative agent

"Coal" disease (anthracnose - from the Greek. Anthrax - coal), black spot - this is the name of the most dangerous infection, the causative agent of which is the melanconia fungus. Spores of Gloeosporium ampelophagum are active at temperatures from 3-5 to 35-40 degrees. That is, the range is so wide that, waking up with the first warmth and an abundance of thawed moisture, the mycelium begins a new life cycle.

Throughout the summer, during prolonged rains, the fungus that has fallen on grapes actively reproduces on all green parts of the vine:

• leaves,
• escapes,
• berries.

Hail, often during heavy rainfall, aggravates the situation: mechanically damaged leaf plates and fruits become easy prey for the parasitic fungus.

In warm, damp weather, the incubation period of anthracnose is reduced to 3 days, and the number of generations increases to 30 per season. Only dry, hot weather stops the spread of infection.

The first autumn fogs are a favorable environment for the intensification of disputes. Affected shoots and berries are mycelium storage in winter. Sclerotia of the anthracnose pathogen on grapes is viable for about 5 years.

Infection results

The uncontrolled spread of the pathogenic fungus causes enormous damage to the grapes. If we imagine the harmful effect of the infection in numbers, then the average consequences of the defeat are as follows:

• the area of ​​the leaf plates absorbing sunlight is reduced by more than 2 times, i.e. the ability to photosynthesis is reduced by half;
• a quarter of damaged shoots die, the growth of the rest slows down by more than 5 times;
• the size and weight of individual berries and brushes as a whole decrease by 2–3 times, the sugar content in fruits is significantly reduced;
• "Coal disease" during flowering can destroy 100% of the crop.

To recognize the grape anthracnose in time and start treatment is a chance to save the plant and get a harvest.

Symptoms

Visually, black spot is determined on all aerial vegetative parts of the vine. Regular examination of the culture, especially during the period favorable for the spread of the pathogenic fungus, will allow to start the fight against the pathogen in a timely manner.

Leaves

Rounded brown necrotic spots, up to 5 mm each, gradually merge into larger ones, destroying the living tissues of the leaf plate. The edges of the markings become angular, the color is from light brown to bright, almost red. The center of the spot dries and falls out, resulting in through holes.

Inexperienced gardeners confuse hail damage with anthracnose ulcers. The difference is that the fungal spots are bordered by a black stripe, and their ragged edges are raised.

The younger the leaf, the more likely it is to be infected with anthracnose. The first ulcers appear along the veins. The sheet is deformed, its development stops. Older coarse greens, the age of which is 30 days or more, are subject to fungal infection much less often, so it is important to protect the vine at the beginning of the season, when there is an active growth of shoots.

Escapes

The fungus on young tender shoots leaves necrotic spots with a purple, almost black border.Cracks run along the stems from the affected areas, through which the infection penetrates deep into the tissues. Shoots corroded by spores to the core are not viable. They break or dry out. The same signs of anthracnose on the ridges, leaf stalks.

Berries

Anthracnose affects fruits at the very beginning of ripening. Dark brown spots have a characteristic black-purple frame, merge, forming one rounded or angular ulcer. The fruit becomes velvety within the border, bursts, deforms.

Prevention

Experienced gardeners have noticed that grape anthracnose affects first of all varieties that are resistant to traditional diseases of the culture - mildew, oidium. A vine with high immunity to these infections does not undergo preventive treatment, because the gardener is confident in the resistance of the variety. As a result, the fruit vine, unprotected from anthracnose, becomes a fertile environment for the spread of the parasite fungus. And the damage from it is much more significant than from diseases that the grape variety successfully resists.

Therefore, growers call for mandatory preventive treatment of all plants, regardless of their immunity to certain fungal infections. An effective measure to prevent grape anthracnose is treatment with a Bordeaux mixture (1%) and other preparations containing copper:

• "Poliram VDG",
• "Mancozeb",
• "Polycarbocin".

These are analogous fungicides - you can choose any of them. The first preventive spraying should be carried out at the stage of shoot growth up to 10 cm.

The listed drugs are used only for the prevention of anthracnose on grapes and are not suitable for the treatment of an active disease.

Adherence to agricultural practices contributes to the formation of a strong plant that can resist infection. Therefore, proper care of grapes is also the prevention of anthracnose:

• correct formation of the vine to avoid thickening, which will ensure adequate ventilation of the vineyard;
• treatment with fungicides before and after flowering;
• mandatory spraying of vines after hail with protective equipment;
• compliance with vineyard hygiene throughout the season (weeding, sanitary pruning, harvesting fallen leaves and fruits);
• removal of pathogenic organisms wintering on infected shoots and fruits from the territory of the vineyard together with plant waste in autumn;
• podzimnyaya processing of shoots and the soil under them with Bordeaux mixture (1%).

Grape anthracnose is very difficult to treat, so gardeners prefer to regularly carry out a set of protective measures to prevent the spread of the pathogen.

Treatment

The fight against infection begins with the removal of affected plant fragments: leaves, shoots, berries. It is impossible to reanimate them - it is more important to remove the spores of the pathogenic fungus from the vine. Cuttings from a plant affected by anthracnose must be burned.

There are no effective folk remedies against the causative agent of black spot, so you must immediately start treating the vineyard with fungicides. The following drugs are used:

• Fundazol,
• "Ordan",
• "Previkur",
• "Cabrio Top",
• "Abiga Peak" and others with a similar action.

The treatment must be repeated every 10-14 days, alternating preparations in order to exclude the addiction of the fungus to the action of the fungicide.

If the gardener had to deal with anthracnose on grapes, it is possible to process the plantings with Nitrofen. The drug is effective against fungal infections, but very toxic, therefore, compliance with dosages and safety precautions is mandatory. The procedure is carried out in the fall, when all work on the site is completed, or in early spring, when the buds are still in full bloom.

Grape anthracnose is a disease that is easier to prevent than to cope with during the growing season without loss of yield. Therefore, the vineyard owner should always be on the alert.