Oidium on grapes: signs and methods of treatment

A disease known to gardeners and gardeners called oidium causes a marsupial fungus. The disease damages the inflorescences, tendrils, leaves and berries of grapes, thrives in dry and hot climates, so in Russia the area of ​​its distribution is limited.

Oidium is known in all countries where grapes are cultivated, it is also called powdery mildew, linen, ashtray. The causative agent of infection in grapes is the fungus Oidium tuckeri.

The defeat in the early stages causes a drop in color, the affected shoots do not have sufficient strength for full ripening, and they may not survive the winter period. Infection with powdery mildew at a later date causes the berry to be coated with a gray-white bloom - all the same necrotic processes occur under it. The fruits begin to crack, the pulp exposes the seeds. If the infection has occurred after the formation of the fruit, then cracking does not occur. Instead, a cobweb ray-like bloom appears on the skin of the fruit. Plaque turns into a transit channel for the penetration of harmful pathogens - various kinds of rot.

In order for the fungus to multiply well, it requires appropriate conditions:

• temperature in the range of 20-25 degrees;
• high humidity at the level of 60-80%;
• dry weather with a long dry period.

At the same time, the minimum temperature for the rhizopus to grow and develop is minus 5 degrees. But at + 30 ° C and above, the fungus dies. The same happens if the humidity level drops below 40%. The mycelium safely survive the winter period in grape buds in order to begin their destructive activity in early spring. Powdery mildew infection is mainly exposed to:

• plantings growing on the banks of reservoirs;
• weakened plants lacking soil moisture;
• thickened plantings experiencing poor ventilation between plants;
• a vine that grows freely, without the formation of bushes on the trellis, which also stimulates increased moisture in foliage and shoots.

Powdery mildew (Oidium) was brought to the Eurasian continent from North America. Powdery was first discovered in England. This was recorded in 1845. It was after this date that the oidium marched triumphantly across the country, occupying the entire continent for five years. As a result, the infection turned into an epidemic, which scientists were able to stop, having discovered a means to combat this "scourge" - sulfur.

During the search for opposition, we found out what threat the oidium grapes pose:

• a sharp decline in productivity;
• unsuitability of grapes for consumption.

All affected areas must be removed, otherwise the pulp, juice, and therefore wine, will have an unpleasant taste and smell of mold. And the fact that infection with powdery mildew provokes the appearance of other pathogens is especially unpleasant.Powdery mildew peaks in mid-summer.

To confirm the results of a visual examination, studies are additionally carried out under a microscope. Cut damaged leaves are prepared: hyphae are separated from the leaf plate with a special needle. A drop of water is applied to a glass slide, hyphae are placed in it and examined under a microscope. Gifs with spores (air-conditioned) stand upright, and spores look like chains.

Preventive treatment of grape plantations is carried out in early spring, immediately after the growth of the vegetative mass begins. This is all the more necessary if the infection has already been observed. Over the years, the fight against powdery mildew has developed many folk methods of struggle, not to mention special fungicidal preparations.

Many people choose folk methods of dealing with powdery mildew. This type of counteraction to Oidium tuckeri attacks is used by active opponents of the use of chemicals on their own sites and fans of environmentally friendly products.

The effectiveness of such funds is noticeably inferior to fungicides, and the treatment has to be carried out several times, however, persistence and perseverance always lead to a positive result.

• Infusion of humus. A week before processing, it is necessary to fill the sifted humus with warm water, cork tightly and put in a dark place for 6 days. Then, after the expiration of the period, the resulting concentrate is filtered and used to treat bushes in cloudy calm weather, it is preferable to do this in the evening. Such spraying is carried out more than once - it is repeated a week later and for the last time - before the beginning of flowering. Particularly affected areas are treated weekly.
• Ash infusion. Half a bucket of wood ash is diluted with 7 liters of water. Next, the solution must be boiled for 20 minutes. After the composition is ready, it is diluted with 7 liters of water and liquid soap is added - 100 g. Treatment with this infusion is recommended to be carried out from the second half of the summer season once a decade.
• Soda solution. This composition consists of several components, it is absolutely safe and can be used during any period of the growing season (flowering, ripening). To prepare it, 5 tablespoons of baking soda are dissolved in hot water, 15-20 drops of iodine are added. The resulting composition is topped up with water, increasing it to 10 liters. After that, a solution of potassium permanganate is added, bringing the liquid to a light pink color. At the end, add 40 ml of dissolved laundry soap.The plantings are treated with soda solution 5 times per season, if necessary, the frequency is increased. The first treatment is carried out 7 days before flowering, then weekly.
• Infusion of horsetail. Horsetail is harvested just before cooking, crushed and filled with water, based on 100 g per 1 liter. The resulting mixture is infused for a day, then boiled for an hour and a half to two hours, filtered, cooled, diluted with water 1: 5 and treated with grapes. The procedures are carried out weekly throughout the growing season. The composition retains its properties for a week if stored in a cool dark place.
• Milk whey solution. The serum is mixed with water 1:10 and weekly sprays are carried out with it.

Measures taken:

• the choice of planting material is the first thing to pay attention to when organizing new plantings, preference should be given to varieties resistant to disease;
• compliance with the minimum distance between bushes and rows: thickening is one of the main provocateurs of the appearance of powdery mildew;
• mandatory timely pruning and pinching, as well as thinning of foliage in the area where the bunches are located;
• a garter, the correct formation of a bush, the organization of trellises and the most optimal arrangement of shoots on it.

Correct watering and weeding are no less important in the general complex of agrotechnical measures - the grapes do not like waterlogging, but need additional irrigation during the dry period. Weeding and mulching will help preserve nutrients in the soil for the vines and keep the soil from drying out and cracking.

The initial treatment is carried out during the swelling of the kidneys. It is during this period that iron sulfate is most well perceived by the plant in an acceptable concentration. Like all other foliar treatments, the procedure should be carried out early in the morning or in the evening in calm weather.

Re-spraying is carried out in the presence of 4-6 leaves on the shoot. This is the time to use sulfur, sulfur-containing formulations. If sulfur is used directly, then it must be ground and sieved, turning the substance into powder. Use 30-40 grams per bucket of water. Spraying with sulfur is not carried out in cold weather - the minimum temperature should be +20 degrees.

If a cold period is established, and it is necessary to get rid of the disease, you can replace sulfur with other drugs indicated in the table.

The main danger during spraying is the plant getting burns from the direct rays of the sun, which is why there are recommendations to spray in the morning or evening hours, when the sun's rays lose their strength.

The list of varieties that successfully resist powdery mildew is very large, so several can be cited as examples:

• Aligote;
• Kara Janjal;
• Semillon;
• "Merlot";
• Malbec;
• "Kishmish of the Vatican";
• all hybrids of the "Delight" variety;
• "Kishmish Zaporozhye";
• "White Miracle";
• Velvet Muscat;
• "Golden Don".

Since fungi from the Rhizopus family are one of the main enemies of grapes, attention is paid not only to the production of countermeasures, but also to selection work. Breeding resistant varieties is included in the list of desired results in the work of breeders.

For a high-quality counteraction to the attacks of fungal organisms, not only plant treatments are needed. Prevention is a mandatory measure, an effective and efficient method of preventing diseases at the site.

The list of preventive measures includes:

• mandatory collection and burning of foliage and diseased bunches;
• sanitary and shaping pruning, the use of copper or iron sulfate for the treatment of covering varieties, as well as adjacent soil.

The next video will tell you about the causes of infection and how to combat powdery mildew on grapes.