Grapes, like any other plant, are prone to diseases, among which rot can be distinguished. It is not considered a common disease, but if the gardener has encountered it at least once, then it takes a lot of effort to get it out. In this article, we will look at the types of rot and how to treat it.
Description and types
The disease is caused by the pycnidial fungi Phoma reniformis and Phoma uvicola. The disease can destroy almost the entire crop, not only the clusters and the fruit-bearing vine are affected, but also the entire shoots. There are several types of rot. The most common among fruit crops is gray rot. It is a danger to all plantings in the garden. Sick grapes cannot be exported and stored. Without treatment, he can die completely.
Gray rot is immediately visible on the fruit in the form of purple spots that spread throughout the brush. Then it begins to die off when a dirty gray coating appears on the berries, which looks like velvet.
If the fungus appeared before the fruit ripened, still on the inflorescences, then they dry up before they start. Because of this disease, the taste of the berry is greatly reduced.
Black rot is very dangerous; vineyards that grow near water bodies are susceptible to the disease. Such rot appears due to mechanical damage to the trunk or fruit. Particularly dangerous are damages that are received in the evening or during a change in moisture and temperature. The disease affects the lower parts of the bush. External signs of the disease appear in May-June. White rot affects the crop by 50%, it can be identified by the light color of the peel, which eventually becomes brown-blue. The entire brush is covered as if with a velvet coating. The infected fruit is unfit for consumption, loses its sweet taste and becomes bitter, after a while the brushes dry out and fall off. Grape varieties that have thin skins are susceptible to acid rot infection. During the ripening period, the juiciest ripe bunches can be subject to the appearance of a fruit fly.
The insect not only feeds on the pulp of grapes, but also dilutes the environment for the occurrence of fungal infections. Signs of the disease can be seen by how the berry deteriorates, it becomes covered with red-brown spots, from which there is a sour vinegar smell. Aspergillus rot destroys the crop almost completely. All bunches of grapes are susceptible to the fungus. The disease is also dangerous for other healthy plants. First, the grape clusters lighten, and then acquire a dark color. The fruits shrink, and then crack, turning into a bluish-brown mass. Root rot is also a fungal disease, a feature of this type of disease is that it has several pathogens. These are pathogenic fungi of a different order. The fungus penetrates under the bark or vine of the grape, then into the trunk and completely resolves the wood. In a diseased plant, the trunk becomes brown.
Contributing factors
The main cause of rot is excessive moisture, which comes from prolonged rains or from excessive watering. The second important factor is the ambient temperature accompanying the fungus. Due to a glut of moisture, the berry swells and cracks. It is eaten by wasps and other garden pests, which contribute to the reproduction of the pathogenic environment.
Thanks to them, the pathogenic fungus enters the berry in the form of spores or mycelium. Due to moisture and weather conditions, it germinates in the plant and spreads to others. The external manifestations of the disease speak about the rate of spread of the fungus in the tissues.
As a rule, these signs are already visible at the end of the disease, when sporulation has begun. It is at this stage that the plant becomes a source of infection.
Main features
Symptoms of rot damage depend on the grape variety. The main manifestation is spots and rot on berries that are not typical for healthy grapes. Due to the development of pathogens, they soften, disintegrate and turn into a mushy mass of various colors. For example, due to gray rot, the berries are first covered with brown spots, and the leaves with a gray coating, then they completely dry out. If the disease began when the grapes were already ripe, then they are covered with dark spots, which then turn brown.
Signs of white rot are a white coating on the affected berries, which decrease in size, and the leaves also become infected and darken over time, then dry out. Sometimes such spots appear on the shoots. If you feel a pungent sour smell from the grapes and see the presence of a large number of midges or wasps, then this is a characteristic sign of acid rot damage to the culture. For root rot, the first sign of the course of the disease is that in the lower part of the bush the leaves become small and yellow, there is no fruiting. The fungus dies if the drought begins, but when moisture enters, it begins to grow again inside the roots of the grapes. In 2-3 years, you can lose a healthy plant.
Than to treat?
Preparations
- For the treatment of any type of rot, the most effective are chemicals. “Topaz” is a systemic fungicide against all types of rot, as well as fungal diseases. It can be used for both preventive and therapeutic purposes. Thanks to the active substance penconazole, the reproduction of the fungus stops by blocking the reproduction of spores. The agent is sprayed with a grape bush, thanks to which its components quickly penetrate into the tissues of the plant. He is not afraid of either temperature extremes or prolonged precipitation. During prophylaxis, the plant is protected for 8 weeks, and for medicinal purposes, its effect lasts up to 14 days. The drug is absolutely safe for humans and bees.
- Paracelsus fungicide can be used to control grape rot to save the plant. This universal systemic contact drug is used not only for treatment, but also for the prevention of the disease. The main active ingredient of the drug is flutriafol, which systemically and contactally fights the disease. When interacting with a phytopathogen, the drug disrupts the synthesis of the cell wall of the fungus and stops the growth of mycelium, and during evaporation a certain cloud is created around the treated culture, which protects the plant from the environment. The agent is absorbed into the tissues of grapes within half an hour after spraying and is evenly distributed inside all its parts, including new shoots. “Paracelsus” is resistant to rain and watering. Keeps the plant from pathogenic fungi and microbes for 45 days. The product interacts well with other pesticides.
- Fungicide “Buzzer” has pronounced protective properties that help not only prevent the disease, but also get rid of its manifestations. It contains fluazinam, which acts on the pathogen in two ways. It inhibits energy exchange in pathogen cells, stops spore germination and their vital activity. To start the action of the drug, you just need to spray it on the plant. Within 7-14 days, it will be protected from damage by rot and pathogenic fungi.
The drug significantly prevails over others, as it does not cause addiction and resistance in pathogen strains. The agent does not have a phytotoxic effect.
Folk remedies
In the fight against rot, you can also use folk methods that are effective only in the initial stages and for the prevention of the disease. Spraying can be done with manganese and soda. Manganese is added to a bucket of water so that it acquires a barely noticeable pink color. 70 g of soda is added to the same solution. The finished product is treated with a bush of grapes in dry and non-sunny weather.
Also, lactic acid bacteria are used to prevent the occurrence of rot. To do this, take whey and dilute it with water 1: 2. The plant is treated with the finished solution. An infusion of garlic is also used to fight the disease. To do this, garlic weighing 100 g is infused in 10 liters of water for a day, and then the bush is treated with a ready-made solution.
Prevention
To avoid the occurrence of the disease, it is necessary to carry out timely and regular preventive measures. The main condition for the healthy growth of grapes is timely pruning, which improves air exchange and access to light. There should be no weeds around the roots of the bush. If a lesion occurs, then it is necessary to dispose of diseased leaves and affected berries.
For preventive purposes, treat the vine bush with copper sulfate or other copper-containing preparation, especially if it has been a rainy summer or hail has passed. If you fertilize your grapes, then select the preparations wisely, do not add organic fertilizers. Watering should be carried out moderately and do it along with loosening the soil. The use of nitrogen fertilizers improves plant immunity.
Sustainable varieties
Grape resistance to rot is shown by red varieties, which contain some compounds that suppress the fungus. The thicker the skin of the berry, the less susceptible it is to infection. Sour varieties of berries are less affected by this disease. Therefore, the less sugar in the berry, the less risk he has to get sick. The lower the density of a bunch of grapes, the better it is ventilated and accessible to light, therefore, it is less susceptible to grape fungus.
The most resistant to rot are the following grape varieties: Riesling, Cardinal, Cabernet Sauvignon, Rkatsiteli and Merlot, Chardonnay.
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