Oidium (pepelitsa), or powdery mildew, is a fungal disease that causes great damage to vineyards and can ruin the crop. However, timely measures and preventive measures reduce the level of risk. It is important for hosts to know which drugs should be used to prevent and control the disease, if the grapes have already become infected.
Oidium - powdery mildew
This disease was brought to Europe (England) from North America. In the middle of the XIX century, it spread to the European vineyards. In the years 1852-1854 he destroyed the harvest in France. After they found a means of combating oidium — sulfur — they managed to stop the spread of the disease.
Powdery mildew infects all grape varieties in Europe. Relative stability is characterized by the varieties “Aligote”, “Merlot”, “Malbec” and some others. They do not have high resistance to Chidonnay, Cabernet-Sauvignon oidium, etc.
When grape shoots start growing, some of them stop growing. The first characteristic symptoms appear:
- foliage begins to curl,
- on it appears a bloom in the form of gray-white dust, which since the beginning of summer affects both sides of the sheet,
- foliage becomes yellow, necrotic,
- the patina extends to flowers and clusters that look as if they have been sprinkled with flour,
- dark spots appear on the shoots, which gradually cover the entire surface,
- tissues of shoots turn black and die off in some places, the smell of rotten fish appears.
Further development of the fungus leads to:
- the death of infected inflorescences,
- the drying of grapes that were previously affected by the disease,
- the cracking and drying of small fruits, the exposure of seeds.
From the leaves Oidium goes to the berries
Description of the pathogen
A fungus of the genus Uncinula, an obligate parasite, appears and develops on the surface of grapes. Thin hyphae attached to the appressorium are attached to it, which form the dusty deposit of a characteristic gray-white shade.
When feeding, the fungus injects haustoria into the cell structure of the plant's epidermis. The affected cells die, forming a mass of dark brown color. The wind carries the conidia of the fungus to the non-infected parts of the grapes. The development of the disease contributes to dampness (humidity 80%, rain) and increased atmospheric pressure. Among other favorable conditions for the fungus - poor ventilation area.
The incubation period of the disease is from a week to two weeks (depending on air temperature). Parasitic cells develop better at 20 degrees, but growth begins at 5 degrees.
Uncinula Fungus - the causative agent of oidium
The chemical that is particularly toxic to the parasite is sulfur. Fungal cells absorb it and die due to the harmful effects of hydrogen sulfide. Neither blue vitriol, nor fungicidal preparations of organic origin, through which winegrowers fight mildew, do not have a detrimental effect on the fungus.
In order to properly act on the parasitic cells, sulfur from the solid state is converted into vapor. This is possible at temperatures of 18 degrees and above, which means the inefficiency of the method in the cold. One procedure will be enough from 100 to 200 grams of sulfur.
Another condition is the size of the sulfur particles, which must be ground very finely. To preserve the properties of the fineness of the substance is stored in a dry closed place.
Spray sulfur on all green parts of the grapes. It should not be used in the heat, because it can burn foliage and fruit. It is better to carry out treatment in the evening or in the morning.
If you choose sulfur-containing combination preparations for spraying (“CabrioTop”), then you can also use them as a means to combat mildew. They are mixed with other fungicides and insecticides. Such solutions rain will not wash away easily.
Sulfur is an effective remedy against oidium
In addition to sulfur and sulfur-containing substances, they fight the disease by means of preparations that are used after the completion of the flowering stage:
- "Karatan" - only after the end of flowering.
Means "Fundazol" does not have an effective effect on adult vines, but is used for use on seeds, chips and seedlings. If last year's oidium, then spring spraying by “Horus” is recommended. The same remedy (or "Strobe") is used in cold weather.
Drug Topaz - one of the chemical agents against oidium
How and when to process
The time of the first processing time is determined in accordance with the scale of the last year infection. With a strong spread of fungus, the grapes are processed after the beginning of the growing season in spring. The fight against oidium is combined with treatment against other diseases and pests.
If the affected area is limited, then the spraying procedure is combined with the first time treatment against fungal mildew disease. In the future, each such operation is carried out together with measures to combat mildew.
When the slightest trace of gray bloom appears on the young fruits, they are immediately pollinated with sulfur, waiting for a dry and warm day. If it is cold and damp, it is treated with a suspension of colloidal sulfur (0.2 percent) or antifungal preparations based on organic matter. Then the clusters are washed.
It is important to keep the waiting time - the time between the last procedure performed and the approximate harvest day. For sulfuric products it is 56 days, and for fungicidal substances it is indicated in the instructions. Grapes, which are constantly affected by oidium, are pollinated or sprayed at intervals of two weeks.
The berries, which form a dense brush, are carefully processed so that the substance penetrates between the fruits. Dipping bunches in a solution of colloidal sulfur helps.
If the cluster is not sprayed carefully, the oidium will spoil the berries
It is important to take measures in advance that will reduce the level of risk and intensity of infection. This will help reduce the effects of chemicals. As measures to prevent the fungus in the greenhouses burn sulfur checkers:
- in the fall, before sheltering,
- in the spring - right after the bushes are opened.
Vines to be cut into cuttings and already prepared chubuki are also placed in the premises to be processed. Greenhouses are closed for two days, then air. On the open ground, the bushes bend down to the ground, cover with polyethylene and burn the saber inside.
Also used mixtures - for processing before flowering:
- water - 8 liters
- “Ridomil Gold” - 2 packs,
- "Topaz" - one ampoule,
- "Ekosil" - forty drops.
For the second preventive procedure, when the fruits grow from a pea, the same composition is taken, but instead of “Ridomil Gold”, “Ordan” is used (25 grams). After 20 days, perform the third operation, using the same mixture.
Doses of substances that are used for prophylactic purposes are one and a half or two times lower than medicinal ones. After the measures taken to prevent infection with oidium, it is possible to obtain healthy strong chubukov.
As a fight to prevent oidium should be mentioned:
- airing the grapes
- autumn harvesting of fallen leaves and other plant residues,
- time spent feeding.
Ecosil is used to prevent oidium.
Also recommend the use of organic products - concentrated saprophytic microflora. For cooking, one-third of the humus is poured into a one-half capacity, which is sieved beforehand. Then add warm water (from 20 to 25 degrees) and cover with dense material. incubated for 5-6 days and periodically mixed. Next, filter and the resulting liquid sprayed plants. The second time spraying carried out in a week, then - before flowering.
Another option is ash infusion (volume - half a bucket) for seven liters of water. Stand a day, then diluted with water one to one and add 100 grams of green soap.
You can also use fresh manure or straw waste, for each part of which take three parts of the water component. Insist on three days. After filtering diluted with three times the volume of water.
Oidium is a xerophytic fungus that spreads rapidly and affects all above-ground parts of grapes. However, the risk of its occurrence and the degree of damage that it causes to a vineyard can be reduced by taking preventive measures and preventing it in time.
Oidium is a fungal disease.affecting shoots and leaves. If conditions are favorable, then it goes to the inflorescences and does not allow them to fully develop and ripen.
Powdery mildew does not spread on dried shoots and leaves, but lives only on living tissues. In the form of mycelium, oidium is located in the cracks of the bark, on the kidneys and winters there. The spores of this disease persist on the leaves and shoots all season. It multiplies very quickly, forming new spores, and spreads throughout the bush, and then moves to neighboring plants.
In regions where spring is early and warm, powdery mildew is activated very early and affects newly grown young shoots. In colder climates, this disease wakes up when leaves appear on a bush.
The biological method of struggle consists in preparation in the spring of saprophytic microflora from humus.
This is done like this.:
- In the 100-liter barrel pour humus, so that he took her third part.
- Fill with water heated to +25 ° C.
- Cover with sacking and, regularly stirring, wait 6 days.
Sulfur is fatal to the parasite. The fungus absorbs it and dies. From the oidium on the grapes for treatment dissolve 100 g of sulfur in water (10 l), and for the prevention - 40 g. This is best done in the morning or in the evening, as in the heat of sulfur burns leaves and fruits. This method works at temperatures above +18 ° C. If the temperature is lower, you can use sulfur-containing drugs, such as "CabrioTop".
There are grape varieties resistant to fungal diseases. These are “Aligote”, “Rkatsiteli”, “Kishmish”, “Merlot”, “Sauvignon”.
Oidium - a malignant fungus, quickly spreading over all above-ground parts of grapes. If measures are taken in a timely manner, the risk of disease can be significantly reduced.