Content
Grape chlorosis is a disease, the main symptom of which is yellowing of the leaves due to the destruction of the green pigment - chlorophyll. The disorder may be due to micronutrient deficiency or viral infection. In the first case, foliar and root feeding is carried out, in the second, the bush has to be destroyed.
Why is chlorosis dangerous?
Chlorosis is a general name for diseases that have similar symptoms but different causes. It affects the leaves of grapes and other crops. It can also spread to shoots and bunches. The danger of chlorosis is that it can lead to several adverse consequences:
- disruption of root nutrition;
- lagging bushes in development;
- decrease in yield;
- deterioration of resistance to adverse conditions, diseases and pests.
When the first signs of chlorosis are detected, it is necessary to clarify the cause, since treatment depends on this. Next, you need to treat the grape bushes with foliar fertilizers, fungicides, or solutions prepared independently according to folk recipes.
Causes of grape chlorosis
The causes of grape chlorosis may be associated with infection and a lack of various microelements. In the first case, the virus penetrates through the soil or through carriers (insect pests). As a result, spots of rich green color appear on the leaf plates. In this case, over time, the plant can infect neighboring bushes, which is dangerous for the entire vineyard and other crops.
Non-infectious chlorosis of grapes is associated with a deficiency of certain elements. It is especially often observed on heavy clay soils, infertile soils with high pH (7.5 or more), i.e. in an alkaline environment. In this case, malnutrition of grapes may be associated with a lack of one or several microelements at once - sulfur, magnesium, zinc, nitrogen and others.
The main reasons that provoke the development of the disease include:
- soil alkalinity;
- clay soil;
- increased content of calcium hydroxide (slaked lime);
- damage to shrubs by disease carriers (soil nematodes, worms);
- unbalanced feeding;
- long-term adverse weather conditions.
There are also objective reasons for grape chlorosis. For example, certain varieties are more susceptible to this disease than others. These include:
- Riesling;
- Black sultana;
- Pinot Franc;
- Saperavi;
- Pinot noir;
- Traminer;
- Aligote and others.
The disease primarily affects the leaves
It is associated with prolonged exposure to stress factors on shrubs (sharp temperature fluctuations, drought, heavy rains, violation of watering norms). The main treatment measures are compliance with growing rules and regular fertilizing.
Types and symptoms of chlorosis
Depending on the cause, there are two types of chlorosis:
- Infectious - also called yellow mosaic.
- Non-infectious - occurs due to a lack or complete absence of compounds of phosphorus, iron and other elements.
In the first case, the main symptom will be the appearance of lemon-yellow or pale spots on the surface of the grape leaf blade. They alternate with green areas, resulting in a kind of “mosaic” pattern. Then the leaves begin to shrink, become deformed, and the edges become asymmetrical.
Infectious (viral) chlorosis of grapes can be detected visually
The first symptoms of damage appear already when young leaves form in April. Then the green color is restored almost completely, and you might think that the disease has stopped. Yellowness remains only along the main veins of the leaves. In fact, the virus continues to infect tissues, and new symptoms appear quite quickly:
- the bush lags behind in development and becomes weak;
- shoots are formed with short nodes;
- pea berries (they become smaller);
- unattractive bunches.
As for the signs of non-infectious chlorosis, they depend on which element is missing. The main symptoms are described in the table.
Type of chlorosis | External signs |
Iron | The foliage turns yellow, but the veins remain green; young leaves are affected first |
Magnesium | The leaves first change color at the edges, after which the disease spreads to the entire surface. The plate may take on a reddish or orange tint |
Sulfuric | Yellowing of the veins, then all leaves. Young leaf blades are the first to suffer |
Nitric | The veins turn white, after which the entire leaf loses color (from the central part to the edges). Leaf blades dry out and fall off |
Calcium | Falling flowers and buds, poor ovary formation |
Methods to combat grape chlorosis
Chlorosis of grape leaves can be treated in different ways. First of all, you need to establish the cause. If the pathology is associated with the spread of a virus, it is almost impossible to cope with it. All that remains is to cut down the bush, burn it, and also destroy fallen leaves and branches and water the tree trunk with a solution of potassium permanganate (1%) or a fungicide.
If the cause is related to a deficiency of an element, it is necessary to determine by external signs which substance the plant is lacking. Then foliar and root feeding is carried out. If it is not possible to reliably diagnose the type of chlorosis, it is advisable to apply a complex fertilizer containing 5-6 microelements.
The main method of treatment is foliar feeding.
Folk remedies
Folk remedies are safe and quite effective in the early stages of grape chlorosis. The following recipes are used for treatment:
- Spraying the leaves with a solution of potassium sulfate (70 g per 10 l) and citric acid (10 g per 10 l).
- Decoction of onion peels – 500 g per 10 l. Boil for a few minutes, leave for three hours, filter and begin processing.
- A solution of ascorbic acid (200 g per 10 l) and ferrous sulfate (100 g per 10 l).
- You can also dig rusty nails into the tree trunk circle or clean off the rust and apply it to the soil. This is an effective way to eliminate iron chlorosis deficiency.
Folk remedies have been used since the beginning of spring. In this case, the treatment should be carried out several times with an interval of five days until the symptoms are completely eliminated.If the yellow spots do not go away, it means that the grapes are affected by infectious (viral) chlorosis. The bush will have to be dug up and destroyed.
Biological preparations for grape chlorosis
Biological agents can be used to treat grape chlorosis. They are effective and safe for humans and plants:
- "Trichodermin";
- "Fitosporin M";
- “Respect 25%”;
- "Strekar" and others.
Fungicides
Treatment of grape chlorosis is carried out with iron sulfate. Other fungicides can be used:
- "Ferrovit";
- "Mik-Reak";
- "Ferrylene."
Agrotechnical techniques
To treat and prevent the disease, various agricultural techniques are used:
- If chlorosis of grape leaves appears even on rooted cuttings, this clearly indicates poor soil condition. The area should be dug up and covered with 5 kg of compost or humus per square meter.
- If there is a lot of clay in the soil, then before planting the seedlings, add up to 1 kg of sand or sawdust (per 1 m2).
- Laying a drainage layer during planting. If the soil is dense, it is advisable to use pipes and crushed stone.
- You can also plant a clover-grass mixture next to the vineyard - such plants help improve the soil structure.
- Compliance with watering norms, taking into account weather conditions and characteristics of the variety.
Grapes should be grown on fertile, loose soils
Preventative treatment
Treatment of grape chlorosis is quite effective, especially if the disease is not advanced. But in any case, it is easier to prevent the development of pathology than to deal with its consequences. The main preventive measure is the application of fertilizers, as well as disinfection of the soil.
The procedure is carried out in early spring, watering the tree trunk with a weak solution of potassium permanganate (concentration 1%).You can also use a solution of fungicide - iron, copper sulfate and other preparations.
As for fertilizers, they must be applied depending on the variety. The general diagram looks like this (quantities are given for a 10 liter bucket of water):
- In mid-April, add ammonium nitrate (10 g), potassium salt (5 g) and superphosphate (20 g).
- Before flowering, use mullein (3 kg) or an infusion of cut grass. However, it is not recommended to consume bird droppings.
- On the eve of the formation of the ovaries, potassium magnesium (10 g) and ammonium nitrate (20 g) are given.
- 2-3 weeks before harvest, superphosphate (20 g) and potassium sulfate (20 g) are added.
- The final fertilizing can be done in September, after harvesting. You will need to add a mixture of boric acid, potassium iodide (1 g each), manganese and zinc sulfates (2 g each), potassium salt (10 g) and superphosphate (20 g).
In spring and autumn, you need to prune old and diseased branches of the bush. It is equally important to carry out preventive treatments against pests that can carry the yellow mosaic virus. To do this, use biological, chemical insecticides and folk remedies (infusion of wood ash, tobacco dust, decoction of potato and tomato tops, infusion of wormwood and others).
Grape varieties resistant to chlorosis
Another effective preventative measure is to choose grape varieties for planting that are resistant to chlorosis. Experts recommend paying attention to the following varieties: Saint Laurent, Pinot Meunier, Chasselas, Portugieser, Müller-Thurgau, Elbling, Muscatel, Liebmerger and others.
Saint Laurent is one of the popular grape varieties resistant to chlorosis
Conclusion
Grape chlorosis most often has non-infectious causes. If you do several treatments with complex preparations, the symptoms of the disease gradually disappear. If a bush is infected with a virus, it must be dug up and burned so that neighboring plants are not harmed.
