Cucumber powdery mildew: causes and ways to combat it

Cucumber powdery mildew treatment and prevention

Powdery mildew (scab) is a plant disease caused by microscopic fungi, often damaging greenhouse cucumbers and the open ground. The fungus responsible for infecting this particular plant is Oidium erysiphoides. The mycelium usually develops in June and affects first the leaves, then the stems and fruits. Timely treatment and preventive measures can help keep the crop and reap the fruit.

Cucumber powdery mildew

How does powdery mildew look like on cucumbers

The disease on cucumbers is easy to recognize by the following characteristic signs:

  • Small white or red spots on the lower leaf plates;
  • The plaque on the petioles, stems;
  • The size of the spots increases, merging;
  • Leaf plates, shoots in white dust;
  • spots turn brown;
  • leaf plates curl, quickly dry up;
  • fruits are deformed, cracked;
  • shoots dry out, darken.

Spores of the fungus look like small brown balls. Wet microclimate in the greenhouse creates the most favorable conditions for its development. Therefore, cucumbers there are more susceptible to disease. The fungus usually overwinters in the vegetation uprooted in the fall. With the onset of spring heat, it wakes up, clinging to the surface of leaf plates and getting drunk on their juice. Its spores germinate quickly, the higher the humidity, the faster, 3-7 days.

Powdery mildew is caused by the fungus Pseudoperonospora cubensis. It is characterized by yellow-green irregular streaked spots on the leaves. Then they become oily, brown. A white-purple patina appears on the underside of the leaf plates. After a few days, the leaves wither away.

If no control measures are taken, the bushes will quickly die.

Causes of fungus: rainy, foggy weather, temperature fluctuations, dense planting, soil with high nitrogen content, frequent watering with cold liquid, untidy weeds in the beds.

Prevention of powdery mildew on cucumbers

To prevent the disease, vegetable gardeners should follow the basic rules:

  • Plant cucumbers in the same plot with a difference of four years (crop rotation);
  • constantly remove the remains of weeds;
  • disinfect the soil with potassium permanganate in the fall;
  • Treat seeds with preparations “Gransil”, “Trichodermin”.
  • Keep the temperature in the greenhouse above +20 ° C;
  • Water bushes under the root with warm water;
  • sprinkle with special preparations (Quadris);
  • Fertilize vegetables moderately;
  • Water, avoiding contact with the leaves and stems;
  • Do not plant vegetables in lowlands, shade;
  • disinfect seeds;
  • fertilize in moderation.

For prevention, seedlings can be sprayed with topaz, strobilus, manganese. Plants should not be planted too densely to ensure air circulation, otherwise the fungus will quickly spread to the other bushes.

Combating powdery mildew on cucumbers

In order to detect the appearance of the fungus in time, it is necessary to periodically inspect the bushes. This way it is easier to get rid of it in the early stage of the disease.

If the fungus is detected, watering and feeding the plants stop, the infected bushes are removed and burned together with the root system. If the plaque is still on the underside of the leaves, they are cut off and destroyed. Plants weed, remove old, diseased parts, cut flower stems. Folk remedies or fungicides are effective treatments.

Biological preparations are popular: Albit, Alirin-B, Gamair, Tiovit Jet. They do not contain toxins and do not harm plants. They are also used for prevention at different stages of development.

False powdery mildew or peronosporosis is destroyed only by chemical means: HOM, Abiga-Pik, Ordan, Quadris, Consento, Previcur.

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Folk remedy for powdery mildew on cucumbers

In the first stage of the disease, folk methods of control are effective. To get rid of the fungus, bushes are sprayed with prepared solutions, mainly in the evening:



application, frequency

Chemical preparations against powdery mildew on cucumbers

In neglected cases, chemical preparations are used, and the vegetables should not be eaten for about 20 days after treatment.

The drug



Mr. Dachnik recommends: Mildew-resistant cucumber varieties

To ensure that the harvest does not suffer, gardeners choose varieties that are immune to powdery mildew and other diseases. Parthenocarpic hybrids are popular now, they tolerate temperature changes well, do not need pollination, and grow in greenhouse conditions and in the open ground. These include:

  • Regina plus F1;
  • Arina F1;
  • Zador F1;
  • Adam F1;
  • Alex F1;
  • Herman;
  • Amur;
  • April;
  • Artist.
  • competitors;
  • creeps F1;
  • spring;
  • Natalie;
  • Phoenix Plus;
  • Tasty;
  • Yerofei;
  • Neshinsky.

Newly bred varieties:

Preventive measures and resistant cucumber varieties can help you avoid fungal diseases and get a good harvest.

What does powdery mildew look like on cucumbers and how to treat it?

Cucumber powdery mildew often affects cucumbers grown both in greenhouses and outdoors. To save the harvest, it is important not only to fight the fungus in time, but also not to forget about preventive measures.

disease description

Powdery mildew, also known as ash, occurs on cucumbers due to the activity of the fungus Oidium erysiphoides, the microorganisms of which are transmitted by airborne droplets. In the greenhouse, the first signs of the disease usually appear on bushes near windows, broken windows or doors that are not closed tightly. In the open ground, the first to contract the disease are plants planted in shady, humid, and crowded places. The disease can appear in any month of the “active” season, i.e., from May to September, although the highest risk is in midsummer. In most cases it occurs a few days after heavy rains. Optimal conditions for fungus development are air temperature of 20-27 degrees and humidity of 50%.

The plant in the first stage of the disease looks as if its leaves are slightly powdered with white flour. By the way, the first signs appear about 4-5 days after infection. Later, the amount of plaque increases, whiteness “crawls” to other leaves and even stems. The upper part of the leaves is covered with small white spots, and the lower part is covered with a loose layer of the same color. If you look closely at the leaf, you can see dark balls on the board – a receptacle with mushroom spores. After they mature, drops of liquid resembling dew are found in this place. The diseased plant is soon covered with rust spots. Gradually their area increases, the plates curl, dry out, and crumble.

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The disease develops “from the bottom up”, i.e. first the first leaves are affected, and then the plant is absorbed completely. If the gardener does not notice the disease in time, even the fruits themselves can die: Due to the disturbance in the absorption of nutrients, they stop growing, and the taste becomes bitter. The fungus pathogen overwinters in the soil and can even exist on plant waste for about 7 years, so it is extremely important to carry out preventive measures to destroy the focus of infection.

It is worth noting that true powdery mildew must be distinguished from improper mildew. Irregular powdery mildew is caused by the appearance of the fungus peronospora. The disease is provoked by high humidity, as in the rainy season, but also requires low temperatures. The symptoms of false powdery mildew are different from the real one: yellow-green spots on the outside of the leaf plates, which later become brown oily, and their turns are covered with a gray-purple plaque. This disease affects only the leaves and plates of the crop, but it also leads to a decrease in yield.

Causes of appearance

Mildew on cucumbers usually appears due to weather conditions: after prolonged rains, temperature spikes or fog. Low light also contributes to the reduction of the immunity of the plant, although it may be sick. However, it is not unreasonable to add that improper care, and even initial planting, can make the situation worse and make infection more likely. Therefore, in powdery mildew” increase planting, frequent watering with cold water, weeding and oversaturation of the soil with nitrogen. Failure to follow the rules of agrotechnics and lack of phosphorus-potassium fertilization is also allowed.

By the way, non-compliance with the rules of crop rotation, that is, growing cucumbers in the same place, affects their immunity for several years.

Control measures

Against powdery mildew usually use folk remedies or with the help of purchased biological or chemical preparations. Experts recommend treating with chemicals only in extreme cases, as a significant part of it can remain in the fruit, which is used later. To act in a timely manner, it is important to regularly inspect the plantings and remind them that it is best to treat the early stage of the lesion.

Once the fungus is detected, the crop must be finished and fertilized. All infested parts are cut off and burned, and plantings are sealed.

Chemical preparations.

Chemicals should be used if most plantations have already fallen victim to mildew. When working with toxic substances, it is important to wear a respirator, gloves and protective clothing. Spraying cucumber is usually sufficient to kill fungi, spores. Against mold, you can use “Baileton”, which provides two months of protection of the plant from reinfestation, and “Topaz” begins to act in 4 hours: plants remain healthy for only a few weeks. The drug contains penconazole, which is dangerous to living things.

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Gertner and Tiovit Jet are used, which contains sulfur and scor, which also increases the bust of plantings. Of course, Fondazole can help, Benomyl of which inhibits the reproduction of fungi. You can treat infected seedbeds with a 20% solution of colloidal sulfur. Such treatment should be carried out in one day without interruption at an air temperature of 20 to 30 degrees.

It is important to note that sulfur is not suitable for treatment of cucumbers in the greenhouse, since even the standard concentration causes dangerous burns under such conditions.

Treatment of plants with toxic copper sulfate can also lead to the necessary results. As a rule, 100 grams of baking powder are added to 75 grams of the substance, according to which they are diluted in 10 liters of water.

Regardless of the chemical, it must be diluted with clean water in the specified concentration. This should be done in a dish not intended for food. Plants should be sprayed abundantly – the liquid should drip from the leaf plates, as after rain. To the culture does not become addicted, the means should be changed alternately. After the use of chemicals, even ripe vegetables can be eaten for about 20 days.

Biological remedies

In order to save cucumbers before mildew, you must first remove the damaged parts of the bush, and then spray the plant with biological preparations. The substances they contain do not inhibit the surrounding microflora, so the recovery of the culture is fast, and after a while new healthy sick leaves appear. Biological preparations are most effective in the early stages of infection. Albit will not only help to get rid of the fungus, but also to stimulate the emergence of new shoots and strengthen the immunity of cucumbers. It is useful to culture “Alirin-B” treated to restore the microbiological composition of the soil.

Well shows itself “Gamair”: it helps to combat powdery bugs, offers the necessary prevention, strengthens the immunity of the plant and makes the soil fertile. The most effective biological preparation is “Bactofit”. However, after its application, the fruit should be rinsed with clean water. Finally, the universal remedy “Fitosporin-M”, which is sold as a paste, powder or suspension, also helps to cope with the disease.

All of the above preparations are environmentally safe and can be used at any phase of plant development. However, to completely destroy the fungus, cucumbers have to be treated several times.

Folk methods

Not all gardeners risk treating cucumbers with chemicals and prefer to use folk methods – cheap and safe. With the help of food sod or mullein, you can be sure that there will be no toxins in the crop, but whether it will be possible to defeat mold is not so unambiguous. Very often leaves are sprayed in a ratio of 1 to 4, diluted with pure water. Such a remedy is first infused for several days, and then diluted again in the same proportions. Treatment of culture with mulchin can be carried out twice a month.

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A solution of marigolds is also popular. Half of a ten-liter bucket is filled with crushed flowers, and then the other half is poured with warm water. After a two-day infusion, 50 grams of soap shavings are added to the solution. This therapeutic agent is suitable for spraying plants that already suffer from brown spots. Manganese solution is prepared from 5 grams of potassium guilt and 10 liters of cooled water. The ready liquid is used for spraying from a sprayer, carried out after watering the plants. It can also be used to water the bushes under the root, calculating that for each cucumber wick there should be 500 milliliters of the agent.

A quick preparation is made of laundry detergent and wood ash. About 50 grams of shavings and 1.2-1.4 kilograms of powder are diluted in 10 liters of water. After stirring the mixture, it can be used to water the beds. Another recipe involves using 2 tablespoons of mustard powder and 10 liters of water, which are heated to 50-60 degrees. The resulting liquid can be used for root canal treatment, as well as for spraying.

Quite an effective remedy is maintained if 60 grams of baking powder and 50 grams of soap shavings are diluted in 10 liters of water. It can be used once every 7 days, but no more than three treatments during the entire growing season. It makes sense to dilute the components of “Gurkeno” with 10 milliliters of alcoholic iodine solution in 10 liters of water.

By the way, you can combine soap, iodine and milk in the recipe. In this case, 20 grams of shavings and 25 drops of iodine are stirred in one liter of milk.

A universal tincture of gufette is also suitable for fighting mold. For its preparation, kilograms of fresh green mass are poured with 10 liters of hot water. The remedy should be brewed for exactly one day, and then boiled for about 2 hours. After straining, the infusion is diluted with water in part 1 to 5. It can be used every 5 days, but no more than three times during the growing season. Weed infusion is suitable for daily treatment. Mowed grass should be watered with water in the proportion of 1 to 1, last three days and dip.

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You can spray the plantations with kefir or milk whey, which are diluted with water in the proportion of 1 to 10. By the way, 30-40 milliliters of ammonia are added. Ammonia reduces the acidity of the milk product and forms ammonium lactate, which in turn contributes to the formation of disease in the “competitors” of millanism. Sore plates must be removed from the bush before treatment begins. First, the solution is poured under the root, using the root zone, so that 0.5 to 1 liter per plant. Then the entire bush is sprayed from the ground.


One important preventive measure is the post-harvest treatment of the greenhouse, especially if the cucumbers in it got sick in the summer. The easiest way is to fumigate the room with a sulfur bomb or the use of preparations containing copper. Sulfuric acid pellets are effective against fungi and bacteria, but make the soil infertile. The same is true of copper-containing preparations. Since pathogens rarely live in the greenhouse itself, in principle, it is sufficient to wash it with a mop with plain water and a small amount of manganese. Water the soil with biological preparations that can kill pathogens but do not impoverish the soil. If there was mulch in the greenhouse, it should be burned.

In addition, a number of other measures should be taken. At the beginning of the season, seeds should be soaked in potassium permanganate or fungicide solution for about 30 minutes. Cucumbers should be watered with warm water, and the temperature in the greenhouse should not fall below 20 degrees. It is important to follow the rules of crop rotation (on the same plot the culture is placed at intervals of 4 years), annually change the topsoil and control the application of nitrogen fertilizers. When growing cucumbers in the open ground before planting seedlings, it is necessary to remove all the soil from the surface and water it with boiling water.

Seedlings should be placed so that in the future there was no overgrowth. It is necessary to weed in time, disinfect the soil in the fall with potassium permanganate, do not spray the leaves and stems when watering, do not plant cucumbers in shaded low-lying places.

Which varieties are resistant?

Another preventive measure is to buy varieties of cucumbers that are resistant to powdery mildew. The most effective in this regard are parthenocarpic hybrids, which tolerate sharp temperature changes, do not require pollination and are ready for cultivation both in the greenhouse and in the open ground. For example, Nemetsky, Amursky, Artiste, Arina F1 and Regina-plus F1 are suitable for planting. Of the bee-pollinated hybrids, Phoenix-plus, Competitor, Delicious, Natalie and Goosebumps F1 are deservedly popular.

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