The causative agent is the marsupial fungus Podosphaera leucotricha Salm. from the order Erysiphales. The disease is widespread in Ukraine, Transcaucasia, Central Asian republics, the North Caucasus, and Moldova. It affects both fruit-bearing and young trees, especially saplings and seedlings in nurseries.
The first signs of the disease may appear very early - at the end of April, in years less favorable for its development - somewhat later (in early or mid-May).
A grayish-white coating appears on young leaves, shoots and inflorescences, which covers the entire apical rosette. This is the so-called primary infection. Then, within 15-20 days, the spores scatter and infect healthy leaves (secondary infection). The appearance of a secondary infection is noted at the end of flowering or immediately after it - spots with plaque on the underside of the leaves, which is usually observed in May-June. The plaque covers the apical part of the shoot.
The disease reaches its maximum development at the end of July. When the buds are laid, the pathogen penetrates them, the mycelium persists until the spring of next year and is the source of the primary infection.
Affected leaves curl, harden, and fall off prematurely. The shoots do not grow, bend and gradually die. On flowers, the disease appears on the buds in the form of a white or dirty-grayish coating. They do not form fruits. A characteristic rusty net appears on the affected fruits, resembling cork tissue formed from mechanical damage, or a net from spraying with fungicides. Fetal development slows down. When infected early, the ovaries fall off.
On the mycelium in spring and summer, conidial sporulation develops, consisting of conidiophores and chains of conodia. The shape of the conidia is ellipsoidal, size 28-30×12 µm. They are spread by wind, insects and cause secondary infections. The incubation period of the disease lasts 4-10 days. Infection occurs especially quickly in warm weather with rain, heavy dew and fog. The development of conidial sporulation can last 45-100 days or more.
By the end of summer, the mycelium becomes denser (mainly on young shoots and petioles), turns brown, and marsupial sporulation appears on its surface, visible to the naked eye in the form of black dots. Cleistothecia with forked and tortuous appendages, dark brown, spherical, 75-100 µm in diameter, contain one bursa (50-70×45-50 µm in size) with 8 spores. The saccospores are unicellular, oval, colorless, 20-25x12-14 µm in size. The marsupial stage of the fungus does not develop infection of great importance, since by spring the cleistothecia are destroyed under the influence of other microorganisms.
The pathogen is preserved during the winter exclusively by the mycelium in the fruits and buds of the affected shoots, from where in the spring it spreads to young leaves, flowers and shoots.
After harsh winters usually the development of powdery mildew is weakened due to the freezing of the mycelium overwintering in the buds. The absolute minimum air temperature (below – 23 °C) and the number of days with temperatures lethal for mycelium can be used as indicators for predicting the intensity of development of the primary infection. The temperature factor is the main factor for weakening the development of powdery mildew in the northern fruit growing zone.
In dense gardens, powdery mildew develops more intensively, since due to poor ventilation of the plantings, the content of conidia in the air sharply increases and its relative humidity is higher. Such gardens require more intensive protection and annual removal of affected shoots.
In young orchards, the intensity of the spread of the disease is 1.5-2 times higher than in fruit-bearing orchards, and in nurseries it is 3-15 times higher than in young orchards, and almost 25 times higher than in fruit-bearing orchards; due to chronic infection, apple tree productivity decreases by more than 20%, seeds - by 50%.
In addition to the apple tree, powdery mildew affects the pear tree, but less strongly.
The varieties Idared, Boyken, Jonathan, Renetnoe Duki, Ondine, Charivne, Yaskrave, Papirovka, Pepin saffron, Renet Landsberg, Renet Simirenko, Cortland are strongly affected by powdery mildew, weakly - Spartan, Enort Kav, Antonovka vulgaris, Calvil snowy, Anise velvet, Melba , Stark, Boskopskaya beauty, Liberty, Freedom, Welsey, Starkrimson, King David, Starking, Wagner, Richard, Zarya Altai, Kiev winter, Auxis, Glory to the winners, Doneshta, Sary Sinap, Renet Champagne. No disease was detected on the varieties James Grieve, Priscilla, Alkmene, Chernomorskoe, Olimpiyskoe, Maya, Aport Zimniy, Grushovka Moskovskaya, Ukrainian Rosemary, and Ukrainian Pineapple. Various resistance of the same variety was observed depending on growing conditions.
Based on resistance to powdery mildew, apple tree rootstocks are divided into immune, relatively resistant and highly susceptible.
Unfortunately, many gardeners are well aware of this plant disease - powdery mildew. She meets on garden trees and bushes, on vegetable crops(cucumbers, zucchini, squash), as well as on many flowers, even indoor ones. Today, all methods of combating powdery mildew can be divided into three groups: the use of fungicides, biofungicides and folk remedies. Read about each of these methods in this article. We will also talk about the prevention of powdery mildew on garden and indoor plants.
Powdery mildew on pumpkin leaves. © Scot Nelson
What is powdery mildew?
What does it look like: Powdery mildew can be recognized by a grayish-white coating or characteristic dark brown balls on the surface of leaves and young stems. Over time, the plaque becomes denser and then turns brown.
What caused: Powdery mildew is a mycelium that lives off the plant. The dark brown balls are her spores.
Pathogens: The name of the disease reflects a description of the symptoms of infection common to different types various imperfect fungi. For example:
- Uncinula necator - causes powdery mildew on grapevines;
- Sphaerotheca mors - on gooseberries;
- Erysiphe graminis - on grain crops;
- Sphaerotheca pannosa forma persicae - on peach;
- Erysiphe communis - on sugar beets;
- Sphaerotheca pannosa Lew. var. rosae Voron. - on a rose;
- Erysiphe cichoracearum, Sphaerotheca fuliginea - on cucurbits.
Why is it dangerous?: Plants lose decorative look. Severely affected plant parts stop growing, turn black and die. Diseased inflorescences do not form ovaries. Even a seemingly minor damage leads to a sharp decrease in winter hardiness of shoots and buds, and as a result, their freezing.
Powdery mildew on tomato leaves. © Scot Nelson When appears: Infection begins in early summer, when spores are released from the fruiting body of the overwintered mushroom.
What contributes: Powdery mildew develops during hot, dry times with sharp fluctuations in temperature and humidity. Sometimes after over-application nitrogen fertilizers, after severe rejuvenating pruning, which significantly reduces the resistance of plants.
How it spreads: By wind or splashing water when watering. In direct contact with a plant of the same species.
Vegetable crops of the pumpkin family suffering from powdery mildew very often lose 50% of their yield, and the quality of the fruit also decreases. It should be noted that cucumbers grown in greenhouses are more affected by the disease in drafts, poor lighting, when the physiological state of the plants deteriorates. As a result, the cucumber's resistance to disease decreases. As a rule, the first outbreaks appear near doors and windows. Entire vines die from the disease, and within a short time all planted plants may die.
Powdery mildew on begonia. © Scot Nelson Prevention and methods of combating powdery mildew
It is important to carry out control measures on time; delay threatens the spread of infection over large areas. Since the evil fungus overwinters on plant debris, the first and necessary measure to combat powdery mildew is cleaning and burning plant waste and crop rotation. Use of resistant and weakly affected plant hybrids.
Overfeeding plants with nitrogenous fertilizers, especially during budding, increases the risk of powdery mildew. Against, fertilizing with phosphorus and potassium fertilizers increases resistance to the powdery mildew pathogen.
The appearance of the disease on currants and gooseberries causes curvature of the shoots, which are stunted in growth, the leaves become small, ugly and, after some time, dry out. On gooseberries, in addition to the shoots, the fruits are also affected; first white and then darkening spots form on them. They stop growing, shrink and may fall off.
The development of the disease is promoted not only by humid, hot weather, but also by excessive application of nitrogen fertilizers and severe anti-aging pruning, which significantly reduce the resistance of plants.
An important condition for combating the disease is spring cutting of affected ends of shoots on gooseberries and currants. Fertilizing with phosphorus and organic fertilizers. During the periods before flowering and after harvesting the fruits, plants need to be treated with fungicides.
On the apple tree, leaves, flowers, and young shoots are affected. Leaves stop growing, curl and fall off. Affected shoots and buds freeze in winter, and the winter hardiness of trees sharply decreases. Powdery mildew is more pronounced on old trees, in neglected, unpruned gardens, and on plants located on southern and southwestern slopes.
In strawberries, raspberries, and rose hips, all above-ground organs become diseased, most often the leaves become coarser, their edges curl in the shape of a boat, exposing the underside, which over time acquires a bronze tint. In late summer - early autumn, such leaves are especially noticeable. A slight powdery coating forms on the berries, and they acquire a specific mushroom smell.
Flower leaves affected by powdery mildew darken and fall off.
On trees, it is necessary to promptly cut out the affected shoots and treat them with fungicides during the bud extension and release phases.
Browning of an apple due to powdery mildew. © Alan Biggs
Use of fungicides
Chemical measures to combat powdery mildew, when applied in a timely and correct manner, are quite effective.
Fungicides (fungus - fungus and caedo - kill) are chemicals used to combat fungal diseases of plants.
Of the modern fungicides against powdery mildew, it is worth noting the following drugs: Bayleton, Zato, Quadris, Rayok, Skor, Tilt, Topaz, Topsin, Tiovit Jet, Fundazim, Fundazol.
There have been cases of the emergence of fungal races resistant to chemicals on some crops, so the development of varieties resistant to powdery mildew is an extremely pressing issue.
Use of biofungicides against powdery mildew
Biofungicides are biological preparations that are designed to protect plants from fungal diseases. They contain live bacterial cultures that suppress the proliferation of pathogenic fungi.
Due to the fact that biofungicides are environmentally friendly, they can be used even during the period of fruit ripening. They are less effective than chemicals, and their effect is limited in time. They are used repeatedly.
The most well-known biofungicides against powdery mildew: Fitosporin-M, Alirin-B, Gamair, Pseudobacterin-2, Planriz.
Powdery mildew on cabbage leaves. © Scot Nelson
Folk remedies against powdery mildew
1st recipe: Dissolve 4 grams of soda ash in 1 liter of water, add 4 grams of soap. Stir thoroughly and spray the plants 2 times at weekly intervals.
2nd recipe: Pour 0.5 cups of ash into 1 liter of boiling water, leave for 2 days, strain, add 4 grams of soap, previously diluted in water. Treat twice with an interval of 7 days. In case of severe damage, more treatments may be required.
3rd recipe: Fresh mullein. To prepare the product you need 1/3 of a bucket fresh manure pour in cold water and leave for 3 days, stirring occasionally. Then filter through a thick cloth and dilute with water in a ratio of 1:10. Plants should be sprayed in the evening to avoid sunburn. A fresh infusion is prepared before each treatment.
4th recipe: Fermented water. To combat powdery mildew, you can use any garden weeds; with their help, the so-called fermented grass is prepared. To do this, fill 1/2 a bucket of finely chopped weeds to the top hot water, mix and leave for several days, then strain through cheesecloth. Spray in the evening.
5th recipe: Sour milk or kefir (yogurt). The spray preparation is prepared from separated fermented milk whey, it is diluted in a ratio of 1:10 with cold water and mixed until a homogeneous solution is obtained. Ready solution fill the sprayer and treat the plants.
We hope that the methods described above for combating powdery mildew will help you fight this unpleasant plant disease. But remember that the best remedy The fight against any disease is prevention.
Powdery mildew is fungal disease, caused by microscopic fungi living in the soil. The disease affects almost all crops, manifesting itself in the form of a white powdery coating on different parts plants. Leaves infected with powdery mildew gradually turn yellow and curl, and new ones appear already deformed. The disease covers large areas, causing the plant to die without timely treatment. Without action, it quickly spreads and infects other crops.
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Description of the disease
The first sign of powdery mildew infection is a whitish coating of mycelium on various parts of the plant. It is the result of the activity of powdery mildew fungi, which invade the culture tissue. In just a few days, the disease affects the lower tier of leaves, they lose turgor, turn yellow and gradually die.
Powdery mildew when zoomed in
If you examine the affected area under magnification, you will notice the formation of ulcers under the attached mycelium. Its cells corrode leaf tissue, so the plant looks sick. White plaque interferes with normal photosynthesis, which further aggravates its condition. To save the plant, it is necessary to get rid of the fungus at the first sign of infection.
Conditions for the occurrence of the disease
Powdery mildew fungus is very common in soil, but the disease occurs only when suitable conditions. In warm and sunny weather and compliance with all rules of agricultural technology, the fungus does not manifest itself. For the development of a colony the following are necessary: favorable conditions:
- Cool weather with high humidity and little sunlight. Such conditions are especially dangerous for plants located outside or on the balcony. For indoor crops, this parameter is not so important.
- High nitrogen content in the soil.
- Too dense plantings.
- Failure to comply with the watering regime. The plant can be watered too often when the earthen ball is still wet, or it can be filled with plenty of water after a long break when the soil is dry. This disrupts the immunity of the crop and creates favorable conditions for the fungus.
The disease can develop when powdery mildew spores are transferred through the air from neighboring specimens or when watered with contaminated water. Sometimes touching is enough sick plant hands, and then touch the healthy one.
Elimination of powdery mildew
The fight against this disease must be carried out comprehensively. First of all, it is necessary to correct errors in caring for the plant:
- Watering can be done only after the soil has dried;
- until the plant is completely healthy, spraying should be avoided;
- until the disease is eliminated, you need to move the culture to a brighter place, if possible;
- plantings that are too dense must be thinned out and leaves touching the ground must be torn off;
- refuse to fertilize during illness, and during the recovery period of the plant, use exclusively potassium-phosphorus fertilizers.
Without correcting errors in care, all further treatment methods will be useless, and symptoms of powdery mildew infection will appear regularly.
How to cure vegetables
Powdery mildew can appear on various vegetable crops. Before use chemicals or folk recipes It is necessary to remove all diseased parts of the plants, and dig up the soil around them if possible.
If white coating appeared on cucumbers, treatment with sulfur powder will help. For every 10 m², use 25 to 30 g of product. A good result is obtained by treatment with a solution of colloidal sulfur, for the preparation of which 30 g of the drug is diluted in 10 liters of water. A lasting effect can be obtained by using modern fungicides - "Oxychom" or "Topaz", which must be used in accordance with the attached instructions.
Powdery mildew on tomatoes can be eliminated by spraying with a solution of sodium humate once every 14 days. At the first signs of infection, a 1% solution of “Baktofit” gives a good result if you treat the diseased plant with it three times with an interval of 7 days. Treatment can be carried out with fungicides such as Quadris, Privent, Strobi or Topaz. To improve the “adhesion” of the solution to the treated plant, a small amount of silicate glue or laundry soap shavings is added to it.
If signs of infection are detected on zucchini, the area should be sprayed with Carboran, Kefalon or sodium phosphate, diluting them according to the instructions. Treatment is carried out once a week.
To destroy signs of disease on eggplants, you can use a solution of soda ash at the rate of 25 g per 5 liters of heated water or any modern fungicide. It is required to carry out 4 or 5 treatments every 10 days.
Peeling strawberries
With this disease, a white coating appears on strawberries on the underside of the leaves. Gradually they curl and acquire a bronze tint. Powdery mildew most severely affects the central part of the leaves and the mustache. In the presence of fungus, berries acquire a moldy smell and become covered with a white coating.
To prevent infection, strawberries need to be thinned and planted on time. For treatment, bushes must be treated with a 1% solution of colloidal sulfur. After flowering or harvesting, you can use Bayleton or Switch according to the attached instructions. When processing, not only the upper part of the leaves is affected, but also the lower part.
How to cure flowers from powdery mildew
The fungal disease affects not only vegetables or berries; flowers can also suffer from it. In mid-summer, a whitish coating can be seen on phlox. In this case, all infected parts must be cut off, and severely damaged plants must be completely destroyed. The remaining specimens should be treated with a 1% solution of colloidal sulfur. To prevent flower beds, it is necessary to mulch with peat or humus. Early spring in order to prevent the disease, it is necessary to carry out 3 treatments of phlox with a 1% solution of Bordeaux mixture with an interval of 14 days.
To prevent the development of powdery mildew on roses, the ground around the bushes should be cleared of weeds and loosened in time. In the fall, after sanitary pruning, all plant remains must be burned and the soil must be dug up. At the first signs of disease, the bushes should be treated with Fitosporin-M, Maxim or Fundazol. In spring and autumn you can use the following solution:
- 10 liters of water;
- 15 g copper oxychloride;
- 50 g soda ash;
- 300 g green soap.
To combat signs of disease on petunia, all infected parts of the flower are first removed and burned. After this, drugs such as “Skorom”, “Topaz” or “Previkur” are used. If a fungal infection appears on flowers grown in pots or containers, it is advisable to change top layer soil onto soil that has been treated with Fitosporin-M.
On violets and violas, the disease spreads to the buds, foliage and stems. This usually happens due to heavy dew or when the soil is oversaturated with nitrogen. For treatment, it is necessary to use a solution of soda ash with the addition of soap or modern means- “Morestan”, “Kuprozan”, “Zineb” or “Topsin-M”.
Folk remedies against fungus
On initial stage illness or as preventive measure treatment with folk remedies gives very good results. If the pathology is in an advanced stage, then it will not be possible to completely get rid of the fungus on plants using such methods.
Among the most famous folk remedies are the following:
Name Preparation How to use Soda ash and soap solution 5 l hot water; 25 g soda ash; 5 g liquid soap. Dissolve drugs in water Cool the solution, spray the plant and top layer of soil. Treatment is carried out every 7 days 2-3 times Copper-soap solution Dilute 5 g in 250 g of hot water copper sulfate. In another bowl, dissolve 50 g of soap in 5 liters of water. Carefully pour the first composition into the second, stirring constantly The resulting emulsion is sprayed on infected plants. A total of 2–3 procedures are performed with an interval of 1 week. Soda-soap solution Dilute 0.5 tsp in 4 liters of water. liquid soap and 1 tbsp. l. baking soda Spray the plants with the solution. Carry out 2–3 procedures with an interval of 1 week Potassium permanganate solution Dissolve 2.5 g of potassium permanganate in 10 liters of water Spray the plants with the prepared solution. Perform 2–3 procedures every 5 days Serum solution Dilute whey with water in a ratio of 1:10 When the serum gets on the plant, it forms a film that makes it difficult for the fungal colony to breathe. With this treatment, the plant receives additional nutrition. Spraying with a whey solution is carried out only in dry weather. Treatment requires 3 treatments every 3 days Horsetail herb decoction Pour 100 g of fresh grass into 1 liter of water for a day. Then boil for 2 hours, cool and dilute with water in an amount of 1:5 For prevention, spraying is carried out regularly - in spring and summer. For treatment at the initial stage, 3-4 treatments are carried out every 5 days Mustard solution Stir 2 tbsp in 10 liters of hot water. l. mustard powder The cooled solution is sprayed or watered on the plants. Ash-soap solution 1 kg of ash is stirred in 10 liters warm water and leave for 3 to 7 days, shaking occasionally. Then the liquid is poured into a clean container, leaving the ash suspension in the bucket. Add a small amount of soap The resulting solution is sprayed on the plants every 3 days. The remaining ash suspension is diluted with 10 liters of water and the bushes are watered Cow dung infusion Rotted manure is mixed with water in a ratio of 1:3. Insist 3 days The resulting infusion is diluted in half with water and sprayed on the plants. Garlic infusion Grind 25 g of garlic and add 1 liter of water. Insist 1 day After filtering, the bushes are sprayed with the solution
A dangerous fungal disease that can harm plants and completely destroy the crop.
How to protect plants from it?
Powdery mildew is caused various types microscopic powdery mildew fungi. It usually affects plants in warm, humid weather at +18...+25 degrees. The fungus actively develops when high humidity air on the dry surface of fabrics in dry weather, without precipitation.
At high average daily temperatures it also develops in conditions of low air humidity.
Spores do not need liquid moisture to germinate, so rain, watering and washing the leaves can stop the spread of the disease.
Powdery mildew affects many crops. The symptoms of the disease (as well as the principles of combating it) are the same in each case. Each pathogen specializes in only one or several plant species. Therefore, there is no need to be afraid that oak powdery mildew will spread to phlox, gooseberries and cucumbers.
Why is powdery mildew dangerous?
Powdery mildew always appears on young plant tissues - leaves, green shoots, petioles, green berries. Further development diseases leads to deterioration of decorativeness, poor winter hardiness, and berry bushes- loss of harvest.
The mycelium, which looks like a thick web, grows quickly, and the spores easily scatter in the form of a white powder similar to flour. When powdery mildew develops during flowering, normal pollination does not occur, so the berries are formed ugly, covered with plaque, and acquire a mushroom taste and smell.
The concentration of spores in the air and the risk of plant infection constantly increases from spring to mid-summer. However, in most plants by this time the leaves are covered with a protective waxy coating - cuticola, and it becomes difficult for fungi to penetrate into living tissue. If measures are taken in time, the disease can be stopped. The infection persists in plant debris and in the roots of affected shoots.
Prevention of powdery mildew
- Mixed planting of unstable crops (phlox, roses, delphinium), refusal to grow a monoculture in one place.
- Creating conditions for plants to freely circulate air. Be sure to break out excess shoots and tie them up.
- Timely removal of shoots with signs of disease, plant debris, fallen leaves.
- Deep tillage of the soil for annual flower and garden crops, as well as between rows.
- Balanced feeding. From the second half of summer - reduce the dose of nitrogen fertilizers. During an outbreak of powdery mildew activity (usually late June - early July), it is better to feed the plants with phosphorus-potassium fertilizers, foliar microelements, and add wood ash.
- Regular watering, sprinkling of leaves and crowns can weaken and even stop the disease. Leaf resistance decreases during drought or due to insufficient watering (for example, caragana, common barberry, maple get sick faster in sandy soil with a lack of moisture).
- Preventive autumn and early spring soil treatment in tree trunk circles with copper-containing preparations.
- Selection of resistant varieties.
- Before flowering and immediately after harvesting, spray the plantings with a soap-copper emulsion (20 g of soap and copper sulfate per 10 liters of water).
- At the initial stage of powdery mildew on shrubs and roses, ash is a great help: the bush is sprayed with water, dusted with ash, and after a couple of hours the plant is thoroughly washed with water again.
- ! Do not use chemicals during the berry ripening period. Potassium permanganate (5g per 10 liters of water) - even for a couple of days, but stop the disease immediately before ripening.
Control measures
Sulfur preparations have been used for a long time to combat powdery mildew. In a fine dispersed form, sulfur is absorbed by fungal cells and, turning into hydrogen sulfide, acts on them as a toxin. Before the leaves bloom, treat the plant with Tiovit Jet or Cumulus DF. Treat bushes with sulfur-containing preparations in the morning or evening hours, since in hot weather burns may occur on leaves and berries. “Talendo” and “Karatan” are good for prevention.
The development of powdery mildew can be suppressed by spraying plants with special preparations based on triazoles (Topaz, Horus, Skor); diseased leaves are first removed before treatment.
The easiest method to combat powdery mildew- weak urea solution. You need to spray in the evening after sunset along the lower and top side leaves.
Repeated spraying with fungicides is carried out after 10-14 days. For greater efficiency It is recommended to alternate medications. Please pay attention special attention trimmed hedges and risk-group plants.
Folk remedies for combating powdery mildew
1. 10% aqueous solution of milk or (to save) whey - spray the grapes once a week and fruit bushes. The milk fat, or possibly whey protein, then serves as food for microorganisms that compete with the powdery mildew for space and eat its spores.
2. Daily infusion of ash(half a bucket of ash per 7 liters of water). Before spraying, dilute with water (1:1) and add 100 g of “green soap” as an adhesive. Water the bushes with a watering can, thoroughly wetting the leaves and clusters. Some colleagues do not infuse the ash, but boil it for 20 minutes.
3. Concentrate of saprophytic microflora. In the spring, fill a 100 liter barrel with 1/3 of the sown humus, fill it with warm (+20...+25 degrees) water, cover it with burlap and keep it warm for 5-6 days, stirring constantly. After 5-6 days, the concentrate is filtered through cheesecloth and poured into a sprayer. For prevention Plants are treated at the "green cone" stage on cloudy days or in the evening. The second treatment is a week later, another one is before flowering.
