Diseases of grapes: what are they and how to fight

Mildew

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

In humid and warm weather, white mushroom fluff soon forms on the underside. A little later, the inflorescences affected by the disease become brown and dry. The berries that appear become bluish, after which they turn into wrinkled brown ones, which is clearly visible in the photo.

This ailment is capable of infecting the vineyard due to such a pest as a fungus belonging to the group of false powdery mildews. This dangerous pest can spend the winter season in fallen leaves, taking the form of spores that germinate in spring, especially in the presence of high humidity. The incubation period of infection in normal weather is approximately 15 - 18 days in mid-May, 12 - 15 at the end of this month, 12 - 14 at the beginning of 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 shoots, it will multiply at night, at temperatures above +12 degrees. The cycle of development of this disease can be repeated about 6 - 8 times a year.

European grape varieties are highly susceptible 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 strengthened with care measures. Cleaning of fallen leaves and plowing have proven themselves excellent in this matter. Also, to combat the disease, the 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. Bordeaux liquid was once considered the most effective remedy for protection and treatment, and copper is still often used by experienced gardeners today. Modern drugs to combat the disease do not contain copper, such fungicides are well suited for regular vineyard treatment. Among them are the funds "Ridomil Gold", "Acrobat MC", "Quadris".

Mildew Disease Video

Oidium

Diseases of grapes in our article are also represented by another dangerous disease called powdery mildew (powdery mildew). This disease, like the previous one, was imported from North America, and already in 1852 it caused a lot of trouble in the wine-growing sector of 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 bloom 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 crops, apple trees, roses, gooseberries.It lives and multiplies on the surface of the plant, then the cells die off and become a mosaic of dark brown color. The incubation period can be from 7 to 14 days, much here depends on the temperature indicators. The fungus thrives in damp and moderately warm weather. In the winter season, it is stored in the kidneys. It is capable of affecting all varieties of European grapes available today.

One of the most 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 helps to destroy the fungus. For the treatment of grapes, it is necessary to transfer it to the form of steam and carry out pollination at a temperature of + 18 degrees and above so that sulfur penetrates into the bushes. Also, in our time, preparations that combine sulfur and an organic fungicide have proven themselves well. Means against powdery mildew, which you can see in the photo - a special contact fungicide based on colloidal sulfur "Tiovit Jet", a systemic fungicide "Topaz", as well as the drug "Skor".

The first treatment is carried out, focusing on the timing of the lesion with this ailment last season. Often spring treatment 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 process the culture in warm, dry weather with a suspension of colloidal sulfur. The period between the last treatment of the vineyard and the harvest should be approximately 56 days. It is recommended to spray the bushes every two weeks.

White rot

This disease can affect the ridges and berries of various grape varieties. The causative agent of the infection rarely infects the leaves, more often you can see longitudinal cracks on the branches, dark spots in the form of rings, ulcers with influxes. A couple of days after heavy rainfall, you can visually notice yellowed berries, which then turn pink-blue, drying ridges, pycnidia of white rot. All this is well shown in the photo, which will help you not to make a mistake with the diagnosis. Berries and bunches diseased with white rot pose a danger to healthy future shoots, since they fall off at the end of the growing season, and the infection remains well 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 you cannot harvest cuttings for seedlings from grape bushes suffering from white rot, as they will root and grow poorly.

After the hail, it is necessary to urgently process the vineyard with the help of such drugs as Fundozol or Kolfugo super. If there are previously sick bushes or varieties that are unstable to disease, experts advise, for protection, to carry out several treatments with the above preparations of grape berries. Preparations that 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 can then normally overwinter.

Gray rot

On the territory of Europe, this harmful representative of fungal pests has existed for many years. Gray rot can affect not only all grape varieties, 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 annual wood. In cold, damp weather, bloom can be seen on young shoots and buds.The berries infected with the disease first become gray-brown, and in wet weather a gray bloom appears, while the bunch is a mushy, ugly lump, which is clearly visible in the photo. In dry weather, the first shriveled berries appear, and when the ridges of the bunch are damaged, it is visually visible that they become greenish-brown in color, and then they can fall off.

The causative agent of the infection can develop even at not very high temperatures. The fungus spends winter on the surface as well as inside the bark, which is one year old. If it has settled well inside the bush, then, subject to high humidity, after 5 days, conidiophores will appear, which will cause a gray bloom. Treatment of this disease is very troublesome, since drugs that affect the causative agent of the infection are best used in advance and constantly.

Soap and Bordeaux liquid used many years ago are today recognized as ineffective, therefore, drugs such as Benomil, Derozal, and Cercobin are used to combat the disease. They get inside 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 products give good results if applied regularly and every two weeks until mid-August. Gray mold damage can also be reduced by shaping, weed control, and by providing the shrubs with adequate growth and development.

Black rot

It manifests itself mainly on the shoots and leaves of plants. Symptoms of the disease begin to appear in May - June, while black or chlorotic spots are clearly visible, as shown in the photo. Over time, they acquire larger sizes, 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 feature of the disease is the whitish-gray color of the wood. The process takes place in the autumn-winter period, all the shoulders, and even the trunk of the culture, can dry out. Most often, the disease affects young shoots in early spring, when it rains outside and the air temperature is about +5 degrees. Berries, when the grapes are affected by black rot, acquire a light brown and then dark purple color.

Symptoms of the disease can appear on leaves and shoots 3-4 weeks after the fungus begins to actively multiply. 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 last 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 will appear. Such drugs as "Tiovit Jet", "Ridomil Gold", "Skor", whose action is aimed at combating infectious agents, have proven themselves well in the treatment of a dangerous ailment.

Chlorosis

Occurs in the presence of an alkaline reaction. Yellowing of the leaves is considered to be characteristic signs of the appearance 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. Not only rainy, but also cold weather is favorable for the spread of chlorosis. In those years when there are more dry days, this ailment appears on grapes much less often. In addition, chlorosis is thought to be caused by iron deficiency.

Almost all varieties of our favorite grapes are equally susceptible to this ailment.In the old fashioned way, many gardeners prefer to use copper sulfate to combat this disease, and also lubricate bark sections in the autumn, spray them 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 all this 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 iron deficiency 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 grape varieties should be expected if not only the cultivation of varieties susceptible to it is avoided, but also the soil conditions are improved, and shallow cultivation is carried out on potentially dangerous soils, and alkaline compounds are avoided when mineral dressing is applied. ...

Video "How to protect grapes from disease"

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