White bloom on grapes

The appearance of white bloom on the grapes is a sign of the disease. If you do not respond in time and do not take the necessary actions, then the vine may even die over time. In this article, we will take a closer look at the causes of white bloom on grapes, preventive measures and treatment.

Causes of appearance

White bloom can appear both on the leaves and on the berries. The root cause is usually various fungal diseases. If a white coating appeared on the green leaves, then the plant could become infected with diseases such as Alternaria, oidium, or downy mildew.

Grapes can become infected with a fungus due to several factors.

• The vine is fairly densely planted. With such a planting, the plants lack nutrients and sunlight, in addition, dew stays on the leaves for a long time.
• Not enough fertilizer. Usually, grapes cannot grow on poor soil, they soon turn yellow and may die altogether. It is the diseased bushes that are covered with fungus. For normal development, grapes need mineral fertilizers. It is worth remembering that excess can also be a cause. For example, a large amount of nitrogen ensures the active growth of greenery, as a result, soft shoots are prone to diseases.
• Lack of proper soil care. Gardeners recommend in the fall, when the berries are harvested, to dig all the soil under the vine to a depth of 30 cm, while leaving the lumps. But weeds all need to be removed. In the spring, the soil needs to be loosened, in addition, this procedure must be performed in the summer to remove the crust after the rainy season, since it is this that prevents the supply of oxygen. And be sure to fertilize the soil with mineral and organic additives.
• The presence of weeds and last year’s foliage. Fallen leaves are not recommended to be left under the grapes, they must be immediately collected and removed, because they may contain insect larvae or fungal spores. In addition, the foliage retains moisture, and in such an environment fungus usually develops.
• Lack of sunlight and fresh air. Usually, in such conditions, the grapes begin to fade, microorganisms begin to multiply on its leaves.
• Bad weather. The plant thrives in areas with limited rainfall. Grapes are not afraid of drought. But nighttime light rains and warm daytime weather contribute to the development of fungal diseases. If the air temperature rises above +30 degrees, then the possibility of infection is significantly reduced.

Important! If the grapes are covered with a white coating at the beginning of the summer period, then there is only one explanation – few chemicals were used in the spring. If the air temperature is about +25 degrees, and the rain lasts more than 6 hours, then these are optimal conditions for the development of fungal diseases.

It is necessary to familiarize yourself with the main diseases, a sign of which is the formation of white plaque on the grapes.

• Oidium. This disease can affect all varieties of grapes without exception. Initially, small white spots become noticeable on the buds, then they appear on leaves, berries and shoots. Over time, the leaves, and inflorescences, and shoots dry out. White spots are already turning into plaque, it seems that the grapes are sprinkled with flour. Anamorphic marsupial fungus is the causative agent of this infectious disease. It reproduces quite actively at high humidity and warm air temperatures, and in winter it is in the waiting phase, nestling in fallen leaves, and attacks again in spring.

• Mildew, or downy mildew. This disease is manifested by the formation of a white fluff on the back of the leaves, later the plaque turns brown. The causative agent of this disease is the fungus Plasmopara viticola. With the development of the disease, not only leaves suffer, but also shoots, inflorescences and ovaries. Poor ventilation, high humidity and warm temperatures are the main causes of this disease. The spores of the fungus can be carried by the wind. The basic rules of prevention, including treatment with Bordeaux liquid, will help prevent the development of the disease.

• Alternaria. With this disease, silvery spots form on the leaves. A metallic sheen appears on the berries, their taste changes. In winter, fungal spores remain in the upper layer of the soil, and in spring they again infect the plant. In addition, this disease can develop on apple trees, potatoes and tomatoes. Gardeners recommend processing “Trichodermin” to cope with alternariosis.

• Aspergillus rot. This disease usually appears on the berries, which are covered with light spots. This kind of rot becomes very active in the heat, when the air temperature exceeds +30 degrees. Initially, the berries begin to crack, then they turn white and turn brown.

• Felt mite, or grape itch. The first signs are white formations on the back of the leaves, which look like felt. When the saliva of the tick hits the leaf, a white fluff is formed, which eventually becomes brown. Ticks mainly affect the lower leaves, but with a strong infection, they can rise higher. These parasites are capable of carrying various infectious diseases. Usually, a tick is visible on a leaf, so when it is detected, it is recommended to proceed to active actions. It can winter in grape buds, and give up to 7 generations per season. Acaricides help to cope with this pest.

• Gray rot. This disease is primarily dangerous for red grapes, since the rot destroys the coloring pigment. In case of damage, the entire bush suffers, a gray or brown tint is formed. If you do not fight this disease, the berries will rot. First of all, unripe fruits that are already spoiled by caterpillars, as well as overripe berries, suffer. In hot weather, gray rot becomes less active.

An excellent preparation is Bordeaux liquid in tandem with liquid soap. If the disease is recognized in the spring, then drugs containing copper can be used.

• Chlorosis. The absence of the required amount of iron is commonly called iron chlorosis. Usually light spots form on the leaf around the veins. It is recommended to spray the grapes with a 0,5% solution of iron sulfate. The reason for the development of chlorosis can be excessively alkaline soil.

Treatment

If a white coating has become noticeable on the grapes, you should immediately proceed to active actions. If fungal diseases are the cause, then the affected parts must be removed. And then it is recommended to treat the vine with fungicides. Many gardeners use a sulfur solution to process grapes, as it is one of the safest.

If the disease has not yet had time to strongly affect the grapes, then the sulfur solution will allow you to defeat the white bloom.

To prepare this solution, you need 10 grams of sulfur per 30 liters of water. The solution should be thoroughly mixed, strained and poured into a sprayer. They need to process both leaves and clusters. External factors must also be taken into account. So, the air temperature should be above +20 degrees on the day of processing, then the sulfur will begin to evaporate, forming a kind of cloud. To avoid sunburn on the leaves of the plant, treatment should be carried out only on a cloudy day, preferably in the morning or evening.

If the disease has spread throughout the grapes, strong chemical fungicides should be considered. It could be Thanos or Ditan.

But they can be used no later than a month before harvest.

If you are looking for biological products that do not harm the environment, then you should opt for products such as Albit, Novosil, Guapsin or Trikhovit. If you are interested in folk remedies, then soda, potassium permanganate, wood ash, whey or iodine are usually used.

To prepare a solution of ash for processing grapes from white plaque, you need to take 1 kg of wood ash in a bucket of water. Further, such a solution should be infused for 72 hours. After that, 1 liter of solution is added to a bucket of water, laundry soap (3 tablespoons), then filtered and proceed to spraying.

preventive measures

To prevent the appearance of white bloom on the grapes, it is recommended to perform the following preventive measures:

• grapes need sanitary pruning, which must be done every spring and autumn;
• all damaged and dead branches should be removed;
• you need to provide good ventilation, so the branches should be tied up;
• all fallen leaves and berries must be removed every autumn so that fungal spores do not accumulate in them;
• cultivation should be carried out every spring and autumn;
• every month it is recommended to spray the vine with a 1% solution of copper sulfate;
• grapes do not like heavy watering, it can only be produced when the soil has become dry about 5 cm deep;
• it is recommended to regularly carry out mineral top dressing using foliar and root methods;
• for preventive purposes, it is worth spraying the vine with a solution of potassium permanganate, for this, 1 potassium permanganate crystals are required per 10 liter of water, the solution should be a pale pink hue, the treatment should be carried out before the grapes bloom;
• if there are already infected plants, then they need to be dug up and burned, and then they dig up the soil, treat it with fungicides and wait 2 years;
• if the grapes are ill with chlorosis, then you need to create maximum air permeability, the soil should be drained and a little expanded clay should be applied, while manure should be abandoned, lupine or alfalfa should be planted nearby, the root system can be treated with iron sulfate, and the leaves with iron chelate;
• for preventive purposes, grapes are treated with fungicides such as Strobi, Falcon or Topaz, about 7 days before flowering should be re-treated, before wintering Bordeaux liquid is used for spraying.