Powdery mildew on an apple tree: reasons, how to fight and what to do for treatment

The most common disease that significantly reduces the yield of fruit trees is powdery mildew. Heat-loving plants grown in temperate climates are at risk, but with uncharacteristic temperatures for the region and increased average annual humidity, powdery mildew appears on apple trees, the most traditional fruit tree in the temperate climate zone.

What is this disease

Fungal disease of garden fruit trees, shrubs, root crops has several names, the most common are:

• bel;
• powdery mildew;
• ashtray.

What looks like a white coating on leaves, flowers, fruits, is the mycelium of microscopic fungi, multiplying exponentially, every day a colony of pathogenic fungi captures more and more surface areas of leaves, bark and other outer parts of the plant.

Spores are easily carried by wind and insects, which, if one tree in the area becomes ill, threatens to develop into a real epidemic of the entire garden.

A fungal disease develops on the bark, leaves and fruits. If at an early stage of defeat in the fight against this scourge, you can save most of the crop, then with the disease of the apple tree at the stage of fruit ripening, losses can be up to 80% of the crop.

Who is the causative agent

Powdery mildew is caused by marsupial fungi of the order Erysiphaceae (erizifaceae), there are more than 700 species that cause powdery plaque - 100. Erysiphe, which causes Oidium, also belongs to this class.

Powdery mildew fungi - pyrenomycetes, each of the agricultural plants is susceptible to damage by representatives of a certain species:

• Blumeria graminis parasitizes cereals.
• Trifolia precipitates legumes.
• Sphaerotheca mors-uvae harms gooseberries and black currants.
• Betae threatens sugar beet yields.
• Cichoracearum spoils potatoes, tobacco, pumpkins.
• Sphaerotheca thrives on roses and other ornamental shrubs.
• Uncinula necator prefers grapes.
• Podosphaera is a common threat to fruit trees, including apple trees.

A feature of parasitic mealy fungi is that their colony lives only as long as the plant is alive. Attached to the surface of a leaf or stem in early summer, fungi will die with it.

Parasitic activity of fungi

Mycelium of disease-causing fungi, superficial with appressoria (suckers). To attach to the leaves, the fungi germinate into the plant cells in short hyphae with haustoria. During the growing season of plants, fungi reproduce by conidia (asexual stage), in a tropical climate it may be the only one. Conidia are arranged in islands or chains.

In a temperate continental climate, mushrooms have 2 stages of development - asexual and sexual (marsupial).

Like all mushrooms, erysiphaceae have fruiting bodies - cleistothecia. On a spherical fungus with a concave apex, there are appendages in the form of simple or branched outgrowths. Each of them contains from 1 to 22 asci, they, in turn, are a container for 2-8 ascospores. With such fertility, the mycelium will conquer the entire fruit tree in a matter of days, if preventive and therapeutic measures are not taken in time.

Distribution area

The mycelium of marsupial fungi that cause leucorrhoea does not tolerate severe frosts, the mycelium can overwinter, provided that it is located deep in the bark of a tree affected in the previous season. Based on the harsh climatic conditions - severe frosts, short dry hot summers, fruit trees grown in Siberia and other northern regions are least affected by powdery mildew.

Practically powdery mildew on fruit trees can be found in any corner of the world, the largest affected areas are observed in countries with a temperate continental climate.

The higher the humidity of the air and soil, the less sunny days in summer, the higher the risk. The most favorable conditions for the spread of pathogenic fungi are the B altic states, the northwestern regions of the Leningrad region and the Moscow region. A little lower, powdery mildew causes damage to the crops of the Krasnodar Territory, Kazakhstan, Uzbekistan, Ukraine, Belarus, and Moldova.

Main causes and factors in the development of the disease

The disease spreads conidially between plants, methodically capturing all new areas on the leaves and bark of an infected tree and neighboring stone fruit, berry, fruit trees and shrubs.

Create a favorable environment for mycelium:

• soils with poor water conductivity;
• lack of sunlight at high air temperatures;
• mild winters with thaws;
• a warm, swift spring after a snowy winter.

Under such natural conditions, mycelium will develop rapidly. During the spore maturation stage, wind and heavy rains will favor breeding and disease transmission.

Signs of tree infection

A white translucent coating formed on the shoots, leaves at the stage of the appearance of the first leaves is a sign of the manifestation of the disease. At the same time, buds that have not yet blossomed begin to wither, deform, turn brown, wither and fall off.

The lesions only initially look white, the development of the disease is evidenced by a denser silver coating, which it seems due to the formation of cleistothecia.

At first, these are rare black dots, at a later stage, the fungal coating becomes brown. White bloom on fruits is a short-term phenomenon. Apples affected by the fungus acquire brown woody spots and veins on the skin.

What is dangerous for a tree

Despite the fact that plaque can be easily wiped off leaves, shoots and even bark, the disease has already affected the epidermal cells of the plant - it has sprouted in them.The hyphae and haustoria remaining inside continue to parasitize, due to which, after a while, the spot becomes gray, brown or purple. The mushroom picker takes all the vital juices from its donor - the leaves dry up, the ovaries do not have time to form, and the existing fruits fall off prematurely or lose their presentation, do not gain the standard weight for the variety.

The mycelium of fungi that cause powdery mildew on apple trees most often does not survive the winter, but under favorable breeding conditions, it can destroy a young seedling that has not grown stronger due to the compaction of the mycelium. Adult apple trees with chronic dew cease to bear fruit long before the end of the characteristic term for the variety.

Note: The incubation period is 4-9 days.

Preparations for powdery mildew on an apple tree

Universal remedy for fungal infections and pests of fruit trees - colloidal sulfur.Trees are sprayed with a two percent solution during the budding period, until the cup of flowers opens. At the end of flowering, for preventive purposes, treatment is carried out with a one percent composition.

When treated with a universal fungicide - Bordeaux mixture, a 3% solution is taken for the first spraying, a 1% solution is required for the second. To effectively protect apple trees from re-infection, the Topaz penconazole preparation is recommended, it penetrates deep into the tissues of the tree and fights the pathogen from the inside, and not just the superficial manifestations of the disease.

Just like Topaz, gardeners are in demand:

• granular urea;
• "Impact";
• Cumulus;
• Tebuconazole;
• "Topsin";
• Fitosporin.

In the absence of specialized chemicals at hand, there are several options for treating an apple tree when the first signs of an ashtray are found.

Folk remedies

Three simple recipes have long been used effectively by amateur gardeners. Proportions recommended for 10 liters of water:

1. 50g soda ash with 40g grated laundry soap.
2. 3 g potassium permanganate (potassium permanganate);
3. "Hom" - copper oxychloride, 40 g.

These products in combination with dressings give a good preventive effect, when a disease occurs, such spraying gives a delay to the gardener for 3-4 days. Severe lesions must be treated with specialized means. Sometimes it makes sense to sacrifice one season's harvest to save a tree.

Control measures

In addition to spraying fungicides three times a season, top dressing must be strictly dosed. Nitrogen fertilizers increase the ability to develop not only agricultural crops, but also the fungi parasitizing them - if the recommended norms of nitrogen fertilizers are exceeded, the mycelium will spread especially quickly.Potash and phosphorus fertilizers reduce its vital activity.

Prevention at the stage of the initial cycle of vegetation is important, but how to deal with powdery mildew during fruit ripening? Folk remedies do not affect the quality of fruits, with an increased risk of infection of the plant with powdery mildew, it is recommended to spray apple trees with potassium permanganate or a solution of soda with laundry soap once every 10-14 days.

If the tree is infected, the manifestations of the disease are not only on the leaves, but also on the branches, trunk, then you can’t do without Topaz or a fungicide similar to it in action. The first 2 sprayings are carried out at intervals of 3-4 days. Further, until the fruit ripens, it is necessary to carry out prophylaxis.

Treatment of an adult tree

Processing a tall apple tree with a dense crown is difficult, spraying is carried out not only on the surface of the leaves, it is necessary to process the branches, trunk, lower part of the leaves.This will require an assistant pumping the solution, and personal protective equipment - goggles, a suit that protects parts of the body as much as possible.

What to do with an apple tree when a whole branch of an adult plant is affected? It is easier to remove and burn it; in such a case, a stepladder, pruner, hacksaw, garden pitch should always be at hand. To prevent the development of powdery mildew after winter from mycelium that has overwintered in the soil:

• Mulch is removed from under the tree.
• In the spring and autumn, whitewashing of the trunk is carried out.
• No last year's leaves and fruits should be on the site.

Disease manifestations on apples do not affect taste, but apples will be less juicy. If it is possible to overcome pathogens with the help of folk remedies or gentle dosages of chemicals, then the crop can be used for food.

Attention! You can find out after what processing apples are suitable for eating on the packaging of professional products. The manufacturer's instructions will be relevant if the recommended proportions are strictly observed during use.

How to save young seedlings

To protect apple seedlings during the planting season, they are soaked for a day in a weak solution of potassium permanganate (potassium permanganate). Water should acquire a light pinkish tint, a strong solution can cause burns, the plant will hurt. To improve the survival rate of a seedling, it is better to use growth stimulants, and it is better to refuse nitrogenous top dressing, because in the first season they do not expect a harvest from an apple tree (on any rootstock).

Prevention

When choosing a site for planting, avoid proximity to plants affected by the fungus, protect it from the leeward side, but do not plant it in the shade of a house or a monolithic fence. Be sure to observe the specific height of the intervals recommended for fruit trees.

Required thinning of the crown, removal of affected and old (non-fruiting) branches, cleaning of fallen leaves and fruits, mulching and whitewashing, application of potash and phosphorus fertilizers.

How to fertilize an apple tree in the fall against the disease?

1-1.5% sodium phosphate solution strengthens the plant, helps to form strong, he althy buds, strengthens the plant's immunity to disease.

Seasonal processing

Phosphate spraying of apple trees and other fruit trees is carried out after harvest, but until the leaves have fallen and turned yellow. The solution is absorbed through the leaf plates, thereby protecting the plant from infection with powdery mildew and other fungal diseases after winter.

On varieties of late-ripening apple trees, the leaves fall off before the tree is harvested, in this case, phosphate must be applied through the soil with the last watering of the season. Thinning the thickening crown of a tree prevents the rapid spread of the disease, whitewashing the trunk makes it difficult for hyphae and haustoria to penetrate into the bark of the plant.

Powdery mildew resistant varieties

For the resistance of the apple tree to certain strains of diseases in plants, as in all living organisms, the gene that is most powerful in apple trees of breeding varieties is responsible:

• Amulet;
• Argo;
• Gloucester;
• Duet;
• Marshmallow;
• Golden summer;
• Carmen;
• Red poppy;
• Red Amber;
• Kupava;
• Linda;
• Mutsu;
• Orion;
• Palette;
• Prestige;
• Dawn;
• Redfri;
• Fannel;
• Union;
• Talida;
• Talisman;
• Fortune;
• Fairy.

This is not a complete list of powdery mildew resistant apple trees. For each of the regions, other varieties with high resistance rates can be found in local nurseries. When choosing an apple variety, it must be remembered that immunity to one disease in an apple tree can be offset by weak resistance to other types of pathogens.

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