Content
Grape diseases most often appear due to a lack of nutrients and improper care. To prevent or cure diseases, you need to study their symptoms and characteristics.
What are the grape diseases?
Grape diseases can be divided into two main groups:
- Infectious. This category includes ailments that occur due to infection with fungal spores or viruses.
- Non-infectious. Such diseases develop on poor soils or due to violation of the rules of care; the plant’s endurance decreases and productivity deteriorates.
Infectious diseases are more dangerous because they are difficult to treat and can completely destroy plantings.To eliminate non-communicable diseases, it is usually enough to reconsider the approach to agricultural practices.
Fungal diseases of grapes
Most often, grapes suffer from infections caused by pathogenic fungi. Diseases usually develop in acidic and waterlogged soils.
Mildew
Among the main diseases of grapes one can note mildew, or downy mildew, which becomes active in the spring at temperatures above 10 °C. It appears as oily light yellow spots on the leaves; over time, they turn into a dry coating on the underside of the leaves. An advanced disease can also affect ripening fruits.
In the early stages, mildew can be cured by spraying with fungicides. It is recommended to use Antrakol, Profit Gold and Ridomil in accordance with the instructions.
Regular weeding of the area and mulching the soil helps to avoid mildew infection.
Oidium or powdery mildew of grapes
Oidium, or powdery mildew, is a fungal disease that leaves a grayish dry coating on the plant plates. Over time, the spots spread to the inflorescences and fruit clusters, small berries quickly die, and large ones crack and begin to rot. The leaves become deformed and become curled. The grape disease appears in the summer, usually in warm, damp weather.
You can cope with the disease with the help of drugs Thanos, Horus and Topaz. To prevent the disease, it is recommended to regularly thin out the plantings, tie the vines to trellises and loosen the rows.
Grape bushes that are not regularly pruned are especially often affected by oidium.
Anthracnose
A dangerous fungus affects the leaves and shoots of grapes. First, brown spots appear on the infected areas, and then the vine begins to crack and gradually die. Dark dots with a black border appear on the berries.
It is recommended to treat grapes for the disease with the drugs Acrobat, Horus and Ridomil. For prevention, it is useful to use Bordeaux mixture. The grapes are sprayed on the leaves at intervals of 1-2 weeks.
The fungus that causes anthracnose overwinters on the affected organs of grapes and can remain active for up to five years.
Alternaria blight
A fungal disease affects green vines and berries. It appears as brownish spots on the leaves with necrotic areas in the center; over time, the plates darken and become moldy. Fruits with Alternaria blight are first covered with a shiny film, and then acquire a brown-gray coating. The crop becomes unsuitable for consumption.
It is necessary to combat grape disease from early spring and throughout the season. The bushes are sprayed with Quadris and Skor, as well as Bordeaux mixture. For prevention, it is necessary to carry out sanitary trimming of plantings annually and remove all plant debris from the site in the fall.
Alternaria blight develops in conditions of heat and high humidity
Black spot (Phomopsis)
A fungal disease leads to the appearance of reddish spots on shoots and leaves; over time, the marks darken and then become discolored. The berries are colored and deformed, and then fall off the brush when touched by the comb. Against the background of black spotting, productivity is greatly reduced.
The disease is difficult to treat, so it is recommended to preventively spray the plantings with Bordeaux mixture and prevent the appearance of fungus.If Phomopsis does develop, severely damaged plants are removed from the site, and the remaining ones are treated with Skor, Horus or Topaz according to the instructions.
Phomopsis infects grapes during the flowering period, but the first symptoms usually appear only by August
Gray rot
Gray rot develops on young buds and shoots and quickly affects all annual branches and green leaves. Leaves a coating on the underside of the plates, on the inflorescences and fruit clusters. When a grape bush is severely affected by the disease, when touched it seems to release a cloud of dust. Gradually, the affected areas of the plant darken and dry out.
The preparations Topaz and Horus are good means of protecting grapes from disease. To prevent the disease, it is important to prevent the soil from becoming waterlogged, since the fungus usually appears in cold and rainy weather.
Grapes especially often suffer from gray rot after careless grafting.
Black rot
With black rot, light brown spots with a dark rim and dots in the center appear on the leaves. The berries suffer from disease mid-ripening. First, a white spot appears on the skin, and then a brownish ring forms around it. Within ten days, the fruit dries up and turns into a dry black mummy filled with fungal spores.
In the early stages, rot can be cured with Ditan, Strobi and Polyram. It is better to remove severely damaged bushes from the site in order to preserve neighboring plants, since the fungus quickly spreads from diseased specimens to healthy ones.
During the first five weeks after flowering, grapes are immune to black rot.
White rot
A grape disease in autumn or late summer attacks half-ripe fruits.At first, small pink spots appear on them, but after a few hours the infected berries wrinkle and darken. Varieties with thin skin and juicy pulp suffer especially often from the disease; the infection quickly spreads throughout the bunch, and a characteristic smell of rot appears.
If affected by the disease, the affected hands are removed and urgently treated with Fundazol or Bordeaux mixture. Preventive spraying is recommended in hot weather and in case of mechanical damage to the fruit.
White rot most often develops on grapes due to sunburn.
Cercospora
The fungal disease manifests itself as an olive bloom and dark spots on the underside of the leaves. Ripening berries wrinkle and harden, and the quality of the harvest and its volume drop significantly. If left untreated, the affected parts of the grapes die. The disease develops most quickly at a temperature of about 30 degrees and in insufficient lighting.
For the treatment of cercospora, Bordeaux mixture and systemic fungicides are used. Severely weakened plants are removed from the site.
Cercospora blight usually affects old or weakened grapes
Verticillium
Verticillium, or wilt, affects grapes in early summer and leads to lethargy and discoloration of shoots. Gradually, the branches die, and spots similar to burns appear on the edges of the leaves. The disease spreads from bottom to top. Berries with verticillium dry out and become mummified, although they can remain on the bushes for a long time.
There are no reliable methods of treating grape disease, so affected plants are simply pruned radically. The most effective prevention of the disease is to till the soil before planting bushes.Typically, wilt spreads to grapes from contaminated soil.
Verticillium fungus can survive up to ten years in soil and plant debris
Viral diseases of grapes
Viruses do not infect grapes as often as fungi, but are considered more dangerous. It is almost impossible to cure affected plants; usually the bushes are either completely eliminated or healthy parts are used for propagation.
Mosaic yellow
Mosaic usually appears in the spring immediately after the leaves bloom. The plates of the plant become yellow in color. In summer, the grape disease may subside a little, and the natural green color will be partially restored, but this will not mean recovery. In some cases, the leaves become deformed and double shortened internodes appear on the shoots, but this does not happen with all varieties.
Viral mosaic leads to gradual degeneration of the vine, reduced yield and infertility of the grapes. The disease cannot be cured, so usually the bushes are eliminated after removing healthy apical shoots for further propagation.
Yellowness in grape mosaic can cover the entire leaf or appear in spots
Vein bordering
A viral disease affects grapes during grafting or through the soil. Symptoms of the disease are golden spots on adult leaves or yellowing of the veins; also, during the flowering period, the buds may dry out and fall off. The harm from the viral disease is that the grapes set fruit worse, the yield is reduced by up to 50%.
Vein fringing cannot be treated; affected grapes must be destroyed
Viral infectious chlorosis
Infectious chlorosis of grapes produces characteristic yellow spots and stripes on the leaves in early summer.It does not cause direct damage to the berries, but as the disease progresses, the bushes begin to bear fruit worse, the harvest becomes smaller and decreases in volume. Since the virus cannot be treated, the infected grapes are destroyed.
Viral chlorosis most often appears on grapes after vaccination
Short Knot
Grape disease can be recognized by linear or heart-shaped patterns on the leaves, shredded and curled leaf blades, and greasy spots with an unpleasant odor. The reason is viral infection of the roots - the plant does not receive enough nutrients. The berries become small, do not ripen completely and fall off prematurely. As with most viruses, the only way to control shortknot is to destroy the infected bushes.
When affected by short-nosed grapes, grapes additionally suffer from insects due to the appearance of a sticky coating.
Necrosis
The viral infection affects the blood vessels of the grapes and disrupts the nutritional processes. The leaves of the plant turn white and die, gradually the bush begins to rot and dies. When affected by necrosis, the grapes are radically cut off or completely removed from the site and burned.
Necrosis disrupts the processes of photosynthesis in leaves and shoots of grapes
Bacterial diseases of grapes
In accordance with the name, bacterial diseases of grapes are provoked by bacteria entering the tissues of the bush. Typically, diseases develop against the background of fungi or mechanical damage to fruits, shoots and root systems.
Oleuron's disease
With Oleuron's disease, black spots appear on the leaves and shoots. The nodes of the grapes become brittle, the buds become deformed, and the buds darken.The development of the shrub slows down, and the yield falls.
In the first stages of the disease, sulfur preparations and Bordeaux mixture 5% can be used. An advanced bacterial infection requires complete destruction of the bush.
Oleuron's disease develops in cold rainy weather and against the background of late frosts
Bacterial cancer
Grapes suffer from bacterial cancer when immunity decreases and after winter shoots freeze. The disease can be recognized by the formation of tubercles on the branches, a decrease in the number of ovaries and drying of the leaves along the edges. As the disease progresses, photosynthesis processes are disrupted and the grapes stop developing.
In the early stages, you can cope with bacterial cancer with the help of the drugs Fitoplasmin and Fitoflavin
Bacteriosis of berries
Among grape diseases in July, bacteriosis is especially dangerous. It develops during the formation of the ovaries and appears as yellow spots on the fruits, which gradually turn into brown-purple dents. The pulp dries out, and in just a week the harvest becomes unfit for consumption.
Most often, bacteriosis occurs when growing grapes under bright sun. It is impossible to cure affected fruits, but the disease can be prevented by providing the bushes with shelter from direct ultraviolet rays.
As part of the prevention of bacteriosis, it is necessary to prevent mechanical damage to the berries
Non-communicable diseases
Hot or too humid weather, lack of water and nutrients in the soil, freezing and sunburn lead to deterioration in the health of grapes. There are several of the most common non-infectious diseases.
Chlorosis
Chlorosis develops against the background of a lack of iron, boron, zinc or manganese.It is expressed in yellowing of the leaf plates between the veins, the shoots of the plant become fragile, and flowering stops. You can get rid of the problem by fertilizing with iron sulfate and complex minerals containing essential microelements.
Chlorosis develops when excess nitrogen is added to the soil.
Comb drying out
The disease can be recognized by dehydration and drying of the ridge of the fruit cluster. Against the background of the disease, the berries develop worse and become smaller, and do not ripen to the end. The disease appears due to infrequent fertilizing and deficiency of potassium and magnesium in the soil.
To prevent the ridge from drying out, it is necessary to add potassium especially often in rainy weather.
Ovary abscission
The ovaries crumble before berries form due to overfeeding with nitrogen, moisture deficiency and lack of pruning of bushes. The grapes do not have enough nutrients for high-quality fruiting, or all resources are directed exclusively to the growth of leaves and shoots.
When the ovary sheds, you need to reconsider the approach to watering and apply potassium-phosphorus fertilizer
Prevention of grape diseases
Grape diseases and the fight against them cause a lot of trouble. It is easier to prevent the occurrence of diseases than to save plantings. To prevent diseases it is necessary:
- choose zoned hardy varieties for a specific region;
- plant grapes in well-lit areas;
- do not allow the soil to dry out or become waterlogged at the roots of the plant;
- regularly feed the grapes and carry out preventive treatments with fungicidal preparations;
- thin out plantings, avoiding thickening;
- Perform preventive pruning annually and remove weak, dry vines.
In winter, it is important to provide good shelter for the grapes to prevent the shoots from freezing. Before planting new bushes on the site, you need to thoroughly disinfect the soil from possible fungi and pests.
Conclusion
Grape diseases can cause serious damage to the crop and lead to the complete death of individual plants. It is recommended to pay special attention to the prevention of fungi and viruses, since treatment is associated with significant difficulties.
