Diseases of grapes: what are and how to fight – plodovie.ru

Mildew

One of the most dangerous fungal diseases for grapes, which can be visually seen in the photo and pictures. This very unpleasant disease was brought to the territory of our country from North America. If timely measures are not taken to combat mildew, then you can end up losing more of the future crop. Signs of such a disease are the presence of yellow, oily-transparent spots on the surface of the leaves.

Under the condition of humid and warm weather, a white mushroom fluff soon forms on the underside. Somewhat later, diseased inflorescences become brown and dry. The berries that appear become a bluish tint, after which they turn into shriveled brown ones, which can be clearly seen in the photo.

This disease is able to affect the vineyard due to such a pest as a fungus belonging to the group of downy mildew. This dangerous pest can spend the winter season in fallen leaves, taking the form of spores that germinate in the spring, especially in the presence of high humidity. The incubation period of infection under normal weather is approximately 15-18 days in mid-May, 12-15 at the end of this month, 12-14 in early June, 9-10 in the middle, 6-7 at the end of June, and also about 5- 6 in August. When the fungus spreads to healthy growth, it will begin to multiply at night, at temperatures above +12 degrees. The cycle of development of this disease can be repeated about 6 – 8 times a year.

Varieties of European grapes show a high degree of susceptibility to this disease. American varieties are considered the most not susceptible to this disease. Mildew treatment is usually carried out with the help of modern chemicals and enhanced with care measures. Cleaning of fallen leaves and plowing have proven themselves in this business. Also, to combat the disease, grapes are processed before and after the flowering period.

Young plantings and vineyards should be sprayed approximately every 10 days, and from mid-June every 7 days. Once upon a time, Bordeaux liquid was considered the most effective remedy for protection and treatment, and copper is often used today by experienced gardeners. Modern drugs to combat the disease do not contain copper in their composition, such fungicides are well suited for regular treatment of the vineyard. Among them are the funds “Ridomil Gold”, “Acrobat MC”, “Kvadris”.

Video “Mildew Disease”

Oidium

Diseases of grapes in our article are also represented by another dangerous disease called oidium (it is also a real powdery mildew). This disease, like the previous one, was brought from North America, and already in 1852 it caused a lot of trouble in the field of viticulture in France. Its presence is evidenced by such signs as shoots that have curly leaves, lag behind the rest in growth and development, and are covered with a grayish-white coating on top. Soon, the diseased clusters begin to die off, and the berries become dry, which is very well shown in the photo.

The causative agent of the infection is a fungus, which is also dangerous for cereals, apple trees, roses, gooseberries. It lives and multiplies on the surface of the plant, then the cells die off and become a dark brown mosaic. The incubation period can be from 7 to 14 days, a lot here depends on temperature indicators. The fungus feels great in damp, as well as moderately warm weather. In the winter season, it is stored in the kidneys. Capable of infecting all varieties of European grapes available today.

One of the effective means of protection can be called a normally ventilated formation of grapes, which can prevent the strong spread of pests. In this case, copper and fungicides are not needed, since sulfur works best, which contributes to the destruction of the fungus. For the treatment of grapes, it is necessary to transfer it into the form of steam and carry out pollination at a temperature of + 18 degrees and above in such a way that sulfur penetrates into the bushes. In our time, preparations that combine sulfur and an organic fungicide have also proven themselves well. Means against oidium, which you can see in the photo – a special contact fungicide based on colloidal sulfur “Thiovit Jet”, systemic fungicide “Topaz”, as well as the drug “Skor”.

The first treatment is carried out, focusing on the timing of the defeat of this disease in the past season. Often, spring processing is combined with spraying against other pests of various grape varieties. If even small signs of powdery mildew are found on unripe berries, it is necessary to treat the culture in warm, dry weather with a suspension of colloidal sulfur. The period between the last treatment of the vineyard and harvest should be approximately 56 days. Shrubs are recommended to be sprayed every two weeks.

White rot

This disease can affect the ridges and berries of grapes of various varieties. The causative agent of the infection rarely affects the leaves, more often you can see longitudinal cracks on the branches, dark spots in the form of rings, ulcers with swells. A couple of days after heavy rainfall, you can visually notice yellowed berries, which then turn pink-blue, drying ridges, white rot pycnidia. All this is well shown in the photo, which will help you not to make a mistake with the diagnosis. Berries and clusters infected with white rot are a danger to healthy future shoots, as they fall off at the end of the growing season, and the infection is well preserved in the ground. The causative agent of the virus is active under conditions of high humidity and temperatures above +24 degrees. The life cycle of a fungus is divided into parasitic and dormant phases.

You should know that it is impossible to harvest cuttings for seedlings from grape bushes suffering from white rot, as they will root and grow poorly.

After the hail, it is urgent to carry out the processing of the vineyard with the help of drugs such as Fundozol or Colfugo Super. If there are previously sick bushes or varieties that are resistant to the disease, experts advise to carry out several treatments with the above preparations of grape berries for protection. Preparations, which include copper, are not able to independently restrain the development of the disease. Another important measure for the prevention of the disease can be called the exclusion of contact of berries and brushes with the ground, since, as mentioned above, it is in it that the fungus is then able to normally overwinter.

Gray mold

On the territory of Europe, this malicious representative of fungal pests has existed for many years. Gray rot can affect not only all varieties of grapes, but also many other crops. This is the only parasite that remains on a diseased bush for a whole year, affecting all its green parts and one-year-old wood. Under the condition of cold damp weather, a plaque can be seen on young shoots and buds. The berries infected with the disease first become gray-brown, and in wet weather a gray coating appears, while the bunch is a mushy, ugly lump, which is clearly seen in the photo. In dry weather, the first shriveled berries appear, and when the ridges of the bunch are damaged, it is visually seen that they become greenish-brown in color, and then may fall off.

The causative agent of infection is able to develop even at a not very high temperature. The fungus spends the winter on the surface, as well as inside the bark, which is one year old. If he settled well inside the bush, then, under the condition of high humidity, after 5 days, conidiophores will appear, which will cause a gray coating. Treatment of this disease is a very troublesome business, since drugs that act on the causative agent of the infection are best used in advance and constantly.

The soap and Bordeaux liquid used many years ago are today recognized as ineffective, therefore, drugs such as Benomyl, Derozal, Cercobin are used to combat the disease. They penetrate the bush and heal the plant from the inside. Chemical control of the disease includes treatment with contact fungicides such as Ronilan and Rovral. These remedies give good results if applied regularly and every two weeks until mid-August. Gray mold infestation can also be reduced by shaping a tall trunk, controlling weeds, and providing the bushes with a normal size area to grow and develop.

Black rot

It appears mainly on the shoots and leaves of plants. Symptoms of the disease begin to appear in May – June, black or chlorotic spots are clearly visible, as shown in the photo. Over time, they become larger, and the leaf blade becomes curly, then tears appear on it, and as a result, the leaves turn yellow and fall off.

On the shoots, signs of the disease appear at the end of flowering, most often affecting the first 6 internodes. A characteristic sign of the disease is the coloring of wood in a whitish-gray color. The process takes place in the autumn-winter period, all shoulders can dry out, and even the trunk of the culture. Most often, the disease affects young shoots in early spring, when it rains outside and the air temperature is about +5 degrees. The berries, when grapes are affected by black rot, acquire a light brown, and then a dark purple color.

Symptoms of the disease can appear on leaves and shoots 3 to 4 weeks after the fungus begins to multiply actively. Treatment of all grape varieties involves chemical protection with modern fungicides. Much here depends on the degree of damage to the vineyard by this disease in the past season. The first few treatments are recommended to be carried out at the moment when about 40% of the buds have already blossomed, and at least three leaves have appeared. Well proven in the treatment of a dangerous disease such drugs as “Thiovit Jet”, “Ridomil Gold”, “Skor”, the action of which is aimed at combating infectious agents.

Chlorosis

Occurs in the presence of an alkaline reaction. Yellowing of the leaves is considered characteristic signs of the onset of the disease, and in severe forms, old leaves become almost colorless. Young leaves acquire a lemon color and, like shoots, lag behind in normal growth, and over time, both of them die off.

Experts believe that the cause of such a disease is the presence of insoluble lime in the ground. Favorable for the spread of chlorosis is not only rainy, but also cold weather. In those years when there are more dry days, this disease appears on the grapes much less frequently. In addition, chlorosis is considered to be caused by iron deficiency.

Almost all varieties of our favorite grapes are equally susceptible to this disease. In the old fashioned way, many gardeners prefer to use copper sulfate to combat this disease, and also lubricate sections of the bark in the autumn, spraying using iron salts. When using such a long-proven method, they take 100 grams of vitriol, mix them with 20 grams of ascorbic acid, dissolving it all in 10 liters of water. For each bush, about 10 – 40 liters of such a solution are needed. Much depends on how old the bush is, and how great the lack of iron is.

Modern drugs “Chelate” and “Fetrilon” work better than the old methods, so experts advise using them today to effectively combat chlorosis. A long-term result from the use of these pest control agents in all varieties of grapes should be expected if not only the cultivation of susceptible varieties is avoided, but also the soil conditions are improved, and in potentially hazardous soils, shallow treatment is carried out, and alkaline compounds are avoided when mineral dressings are applied. .

Video “How to protect grapes from diseases”

From the video you will learn tips from experienced gardeners on how to properly protect grapes from diseases and pests.