Infection of grape vines with mildew can ruin the entire crop, so the harmful fungus is actively propagated.
But modern fungicide treatments are able to protect even varieties prone to disease.
Signs of mildew on grapes
On the foliage:
Primary signs of mildew: well visible yellow or brown spots on the leaves of the grape appear, seemingly oily in appearance. On young foliage, they are about the size of a penny, look like circles, on the old one, the angular patches affected by fungus stretch along the veins.
After a time, a mycelium appears in the form of a white cannon on the back of the stained areas.
Gradually infected leaves curl, curl.
Synonyms for the name mildew on grapes are: downy powdery mildew of grapes, Plasmopara Viticola, Plasmopara viticola Berl. et Toni, mildew, and transcription variants: mildew, mildew
On bunches:
Inflorescences acquire unhealthy yellowness. Brushes curled, turn brown. Not formed dry out.
Fruits that have managed to outgrow the size of a pea, but have not yet had good sweetness, become bluish in color, then turn brown and look like a blown-out ball with visible wrinkles.
Mycelium is equally well developed on all parts of the vine.
A photo
For more information, look like mildew grapes can be in the photo below:
And the following photo describes in detail the cycle of propagation of downy mildew:
The causes of the disease
Mildew - a formidable, rapidly spreading disease of European vineyards.
Develops due to fungus Plasmopar Viticola, which appeared in Europe in 1878 because of non-compliance with quarantine measures for wild grapes brought to French farmers by American seedlings phylloxera.
For two years, signs of infection of the vineyards with mildew were found not only in many vines in the south of France, but also in the plantings of Balkan and Caucasian wine-growers.
Fungal zoospores overwinter in the ground. On the vines fall along with sprays that form from raindrops hitting the ground.
Secondary infection from the sick area to the healthy, occurs both with rain and with the help of the wind.
From the moment the spore hits the leaves until the first signs appear, 4 days pass if the air temperature is above 24 degrees.
Methods of struggle and methods of treatment
The proper effect is provided only by timely preventive measures, since when spore falls into the leaves, it is incredibly difficult to fight the disease.
Required procedures:
The eradicating spraying of the soil under the vine should be carried out before the first spring rain, as soon as the vines are tied up and the soil is loosened. As a measure to combat mildew grapes use nitrofen, spreading 400 g per ten-liter bucket of water.
After tillage with a disinfectant, the soil is mulched. On the one hand, this will give an additional protective layer between the vine and the fungus hibernating in the ground, on the other hand, it will soften the blows of raindrops on the ground.
Treat grapes for mildew by foliar spraying with systemic fungicide Ridomilwhen 4 leaves appeared on the vine.
Back-spraying the crests of future clusters with Bordeaux liquid before the formed tassels begin to bloom will help to save the ovaries and protect against mildew before their maturation.
Prevention
To protect the grapes from mildew:
In the fall burn all affected foliage, shoots (if the disease has already manifested itself on the vine).
For sanitization spray the soil: iron or copper sulphateBy making the composition according to the instructions, these folk remedies help to fight the mildew of the grapes and slow down the spread. In the spring, the soil is sprayed with a fungicide immediately after loosening the soil under the grapes.
Even mildew-resistant grape varieties are treated at least twice: first along the first leaves, then along the yet not flowered tassels, after having removed excess foliage (if any) from the bush.
Do not let the overgrown vines prone to excessive foliage formation. When planting seedlings, make sure that the ridge was not thickened.
Do not plant specimens without immunity to mildew, if you are afraid that you will not be able to spray them in a timely manner. Make sure the plants get enough potassium.
When mildew appears on grapes in the neighboring area, urgently need preventive treatment on their vines, so secondary infection is possible with the help of the wind.
Copper-containing solutions can be replaced with drugs: Ditan M-45, Mancotseb, Polycarbacin. This method will help to save grapes from mildew, which are sensitive to elevated copper content in protective preparations.
In the rainy summer, the number of treatments is increased using contact systemic drugs: Oxyh, Ridopolich, Mitsu. The permissible number of treatments per season is 8 times.
A month before the crop ripens, the treatment against mildew is stopped.
Vulnerable varieties
The most mildew-sensitive grape varieties:
- Cardinal
- Iranian Shahin
- Kishmish radiant
- Early Magaracha
- Special
- Rizamat
Grape mildew is an insidious disease, only “waiting” for the gardener to make a mistake and delay with preventive measures against this American fungus. Therefore, if last year the disease took away a part of the harvest, then the next year, be vigilant. Do not let the spores, wintering in the ground and fallen leaves, which remain viable for 5 years, again "eat" your grapes.
