Mildew and oidium on grapes: causes and control measures

A healthy, beautiful vineyard is the pride of any gardener, paying back all the costs of effort and money. But 2 insidious enemies of grapes can interfere with enjoying the harvest, from the names of which any knowledgeable person will shudder – mildew and oidium. This couple of fungi can ruin life for more than one season. Adds problems that a beginner can confuse them and, having missed precious time, treating grapes for the wrong disease, lose the crop. Timely detection of the disease is half of the successful fight against it. We will tell you what these “monsters” are, how to distinguish them, what to do so that the risk of meeting them is minimal.

Mildew and oidium on grapes: causes and control measures

How to distinguish diseases from each other?

To distinguish between these diseases, you need to understand what each of them is and what unique signs it has. Let’s start with mildew.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Mildew

She is also downy mildew, downy mildew or peronospora viticola de Bary. The disease was brought to Europe (south of France) from America at the end of the XNUMXth century and quickly became a problem for the entire continent. Mildew became one of the key causes of the crisis and decline of vineyards in the late XIX – early XX century.

This disease is the most common in cultivated grapes. Its causative agent is the fungus-like organism Plasmopara viticola, which is part of the class of oomycetes.

Mildew zoospores love a drip-humid environment, which makes the period of heavy rains the most favorable time for the spread of infection. The most dangerous period is the end of spring and the beginning of summer. The fungus overwinters in the soil and the foliage remaining on the ground, it enters the plants with rain spray. The incubation period of the disease is 12-18 days. After this, asexual sporulation of pathogens begins.

Mildew develops rapidly – a healthy plant the next morning can already be completely affected by the disease. Mildew affects all green parts of grapes. Even if the disease does not kill the bush, it will negatively affect the taste of the berries, reducing sugar content and acidity.

In addition, the transferred disease affects the winter hardiness of the plant.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Symptoms are as follows:

  • the upper side of the leaves becomes oily, yellow, covered with reddish or brown spots;
  • a barely noticeable fluffy whitish coating forms on the underside of the leaves;
  • young leaves wither and fall off as the disease develops;
  • characteristic signs of mildew on grape leaves at the end of the growing season – the rapid death of the leaf and sporulation on its back side;
  • a thick white coating forms on inflorescences and berries;
  • young berries darken and fall off, mature ones shrivel and turn blue;
  • depressed light spots form near the stalks;
  • shoots become covered with gray and brown spots, begin to dry out.

All European varieties of grapes are extremely susceptible to mildew, while American varieties have significantly higher immunity.

Among the resistant varieties are the Vostorg group, the varieties Aladdin, Talisman, Galahad and Harold.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Oidium

Oidium is a disease called powdery mildew in other cultures. Fungal disease, the causative agent is Uncinula nector, a marsupial fungus. Like mildew, it came to Europe from North America, but it happened almost half a century earlier – in 1845.

The oidium causative agent loves heat, the most favorable temperature for the development of the fungus is 25-30 ° C. The incubation period is 7-14 days. The infection lives in the soil, affected buds and shoots. If the planting is dense, and there are already a lot of leaves on the grapes, oidium can very quickly destroy the entire vineyard.

Diseases can be facilitated by tying grapes to old, rotting trellises and a sudden change in weather.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

The symptoms are:

  • affected foliage looks curly;
  • the leaves are covered with a whitish-gray bloom, spreading over the entire surface of the leaf over time;
  • the upper part of the stems, clusters and inflorescences are covered with an ash-like coating;
  • inflorescences and berries affected by the fungus dry up;
  • brown spots form on the shoots;
  • young berries crack;
  • an unpleasant odor emanates from the plant, similar to that of a rotting fish.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Oidium affects all varieties of grapes, but European ones are most susceptible to it. The varieties Vostorg, Talisman, Timur, Alexa, Kishmish Zaporozhsky, Victoria, Kavkaz, Golden Don, New York Muscat, Mars, ” Alden Amethyst”, “Lancelot” and others.

The diseases are not as similar as it might seem at first glance. They differ in symptoms, they have different pathogens. But the common thing remains that they are able to completely destroy the crop, if you do not engage in prevention and do not start treatment on time.

Now let’s move on to the main question – how to treat plants affected by this scourge.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Mildew treatment

It is necessary to fight against mildew in a complex way, combining the proper care of the vineyard, preventive measures and chemical methods of protection. It is important to remember that it is necessary to process grapes from mildew, alternating means with different active ingredients, otherwise the fungus will develop resistance.

For a long time, copper was the main active ingredient, but now quite a few other active ingredients have appeared on the market. Popular mildew treatment regimens are the use of a mixture of Bordeaux and colloidal liquid, a decoction of lime with sulfur, and various fungicides, which will be discussed below.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Fight against oidium

The main enemy of oidium became known in the XNUMXth century. They turned out to be sulfur. Accordingly, if the measures for the prevention of mildew and oidium are almost the same, then when choosing chemistry for treating plants, you will encounter differences. The ideal option would be to spray the bushes with compounds that include both sulfur and copper or a fungicide.

Spraying bushes with sulfur remains a fairly popular method of treating and preventing oidium. When working with sulfur, it is important to remember a few nuances.

  • Sulfur treatment is effective only at an air temperature of at least 20°C.
  • Do not use sulfur in the sun – there is a risk of burning the leaves.
  • Damp sulfur cannot be used.

The development of the disease is not affected by the use of growth stimulants, although there is a misconception among gardeners that these substances can promote the development of the fungus.

It’s not about stimulants, but about their effect – the development of dense foliage, which needs to be thinned out more often than it was done before the use of the drug, which the vineyard owners forget about.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Preparations

Let’s go through the main drugs recommended for the prevention and treatment of mildew and oidium.

  • Pennkozeb – contact fungicide with the addition of trace elements. Suitable for treating mildew.
  • «Topaz 100 ES» – a drug that gives the maximum effect in the treatment of fungal diseases of grapes. The effectiveness of its use at a concentration of 2,5 ml per 10 liters of water is 80%.
  • “Ridomil Gold MC, VDG” – systemic-contact two-component fungicide. Recommended for preventive treatment of grapes from mildew after the flowering period.
  • Concento – although this fungicide is used to treat late blight, it can also help in the fight against mildew.
  • Horus – a systemic agent of local action used in the fight against fungi.
  • inkstone – a classic drug with a wide spectrum of action. Important! It is not used together with phosphorus-containing products.
  • Copper sulfate – Another old friend of gardeners. Contains, as expected, copper.
  • Talendo – but this drug is relatively new and not familiar to everyone. Effective for prevention.
  • Ecosil – a fairly light drug. It is used to regulate plant growth, but can also be used to strengthen the defense of grapes, as it has some fungicide properties.
  • “Karatan” – a narrowly targeted contact preparation for the treatment and prevention of oidium, inhibits the growth of the pathogen fungus.
  • “Switch” – a systemic contact antifungal drug.
  • Azophos – an environmentally friendly antifungal drug of a new generation.

We will talk about the frequency of processing below, but for now we recall that the last time pesticides can be used in the vineyard is a couple of months before harvest.

Folk remedies

If you are afraid to use chemicals, you can take a chance and try to cope with diseases with folk methods. Here are the best ones that have stood the test of time.

Mildew and oidium on grapes: causes and control measures

From mildew

Extract from wood ash

Composition:

  • 1 l of sifted ash;
  • 50 g of laundry soap;
  • 10 L of water.

Dissolve the ash in water and let it brew for 5-7 days. Strain. Add grated soap.

Process the grapes with the composition every 7 days until the end of autumn.

Mildew and oidium on grapes: causes and control measures

From the oidium

Mowed grass

Composition:

  • grass;
  • a bucket of water.

The cut grass should be raked into a heap. When a grayish mold appears on it, place it in a bucket and fill it with water. Hold on for a couple of hours. Strain.

The composition must be regularly sprayed with grape bushes until the beginning of autumn.

Mildew and oidium on grapes: causes and control measures

Mildew and oidium on grapes: causes and control measures

Mullein

Composition:

  • 2-3 kg of mullein;
  • 1 teaspoon of urea;
  • a bucket of water.

Soak the mullein in water for 2-3 days. Strain the resulting infusion. Add urea.

Treat the grape leaves on both sides with the tool.

Mildew and oidium on grapes: causes and control measures

Маргацовка

5 g of potassium permanganate should be diluted in a bucket of water, sprayed with grape bushes.

Mildew and oidium on grapes: causes and control measures

Milk

1 liter of milk or whey is poured into a bucket of water. The leaves are sprayed with the mixture.

In addition to these recipes, for prevention, you can use an infusion of garlic or iodized salt. If the infection is detected at the initial stage, you can try to cope with it with a solution of soda at a concentration of 0,5%.

Baking soda can slow down the development of fungus.

Mildew and oidium on grapes: causes and control measures

Preventive measures

Unfortunately, there is very little chance of coping with these sores without using chemistry at all. But it is possible to strengthen the protection of plants with proper care and timely prevention. Disinfection of vines and soil with vitriol at the beginning of spring, contrary to popular belief, is not an effective protective measure – the same oidium develops in the depths of the kidney, from where it is very difficult to expel it by washing.

From time to time, in dry weather, you need to pluck a few grape leaves, especially if they have suspicious spots on them. Plucked leaves should be placed upside down on a damp sheet of paper.

If a plaque appears on the back of the spots, the plant is affected by mildew.

Mildew and oidium on grapes: causes and control measures

The main measures are as follows.

  • Do not plant varieties with varying degrees of protection against mildew and oidium in the immediate vicinity. This will complicate the processing of plants.
  • Give preference to varieties with greater resistance, since there are enough of them.
  • Landing should not be too thick.
  • Stepchildren must be removed in time.
  • Do not oversaturate the soil with fertilizers with a high nitrogen content.
  • Rotting berries, rotten foliage, other waste should not be left lying near the bushes.
  • The fragment must be done in a timely manner so that the crowns are ventilated.

Mildew and oidium on grapes: causes and control measures

Regarding preventive treatment with contact and systemic fungicides, it should be done 3 times:

  • with a length of young shoots of 15-20 cm;
  • just before flowering;
  • when the berries are the size of a pea.

In mid-May, if the temperature reaches 13 ° C, after the first heavy rain, additional processing is mandatory. If the grapes were hit last year, then another spraying is done when 3-4 leaves appeared on the bushes, regardless of the air temperature. The main means used for preventive spraying: “Switch”, “Karatan” and “Talendo”.

Do not forget about the timely prevention of fungal diseases, properly care for plantings. Then the meeting with the “sores” will take place for the vineyard with minimal losses, and the planting will continue to please with a harvest and a healthy look.

Mildew and oidium on grapes: causes and control measures

Anna Evans

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