An experienced farmer knows that an early and decent crop of cucumbers can only be obtained in greenhouse conditions. But sheltered soil is not always a guarantee of plant health. The review will discuss why white plaque sometimes appears on such cucumbers, how to deal with this problem, and even better - to prevent its occurrence.

Conditions in the greenhouse for the growth of cucumbers

The advantages of growing cucumbers in a greenhouse are obvious: under a protective film, a heat-loving and very tender plant, especially in the early stages of development, is not afraid of sudden changes in temperature and sudden cooling, which are so characteristic of variable spring weather.

However, not all gardeners know that the technology for caring for cucumbers growing in a greenhouse has features compared to growing this crop in open ground. These features are reduced to the following rules:

1. Lighting. With early planting of seedlings, the cucumber bed should be additionally lit, since natural light during this period is not enough for the development of the bush and the laying of greenhouses. To illuminate every 10 m², one 600 W lamp must be installed. If the area of ​​the greenhouse is less than 7 m², one 400 W lamp is sufficient. If there is not enough light in the greenhouse, it is necessary to adjust the temperature in the direction of its decrease. In this case, cucumbers will develop more slowly, but their immunity as a whole will not be affected.
2. Temperature condition. Directly depends on the phase of the vegetative development of the culture. So, at the stage of laying the seeds, the soil should be warmed up by at least + 24 ° C, the air should be about three degrees more, and there should be no differences between day and night temperatures. After emergence, the temperature of the air and soil should be approximately the same, at + 24 ° С, then after 5-6 days this indicator decreases by a couple of degrees. After landing at a constant place, the temperature of the air and soil (taking into account daily fluctuations) should be + 19 ... + 21 ° С.
3. Watering. In winter, the procedure is carried out in the morning on the brightest days. In the warmer months, irrigation frequency is about once every 2–4 days, depending on the light intensity. Water should always be warm.
4. Soil care. To prevent the development of fungal diseases of the root system, the soil on the garden bed must be carefully loosened after each watering (trying not to damage the surface roots of cucumbers) or use mulching technology.
5. Air humidity. At the stage of emergence of seedlings, this indicator should be 90–95%, however, after the formation of the first true leaf, the humidity decreases, but not more than 10%, otherwise the leaves are deformed and dry.
6. Ventilation. When growing in open ground, problems with stagnation of air in the garden cannot occur, however, when covering cucumbers with film, inexperienced farmers often forget about the need to regularly ventilate the greenhouse, which makes the plants sick.
7. Top dressing. The fertilizer application recommended for greenhouse cucumbers involves a fivefold implementation of this procedure during the season using organics (chicken droppings or mullein), as well as complex mineral fertilizers.

The reasons for the appearance of white plaque on cucumbers

White plaque on cucumbers can be a symptom of various diseases, however, if you try to systematize the most likely causes of culture damage by a particular disease, then in most cases these reasons are associated with:

1. Sunburned leaves. The problem arises due to improper watering, namely, dropping water on a leaf plate during the period when the plant is illuminated by the bright sun.
2. Violation of the temperature regime. At air temperatures below + 15 ° C, the development of cucumbers slows down, at + 10 ° C it stops. If the air heats above + 30 ° C, all the bush energy is directed to fight overheating. Both too cold and too warm air create stressful conditions for the culture, as a result of which it becomes less protected against pests and diseases of any nature - viral, bacterial, fungal.
3. Excessive or insufficient humidity. Too dry air weakens the protective properties of the bush, which is forced to spend all its strength on surviving in adverse conditions, however, increased humidity is also undesirable and dangerous, since it stimulates the development of most pathogenic fungi that are pathogens.
4. Excess or lack of moisture in the soil. The roots of cucumbers cannot extract the nutrients necessary for development, but when the water stagnates in the roots, their oxygen starvation occurs and, as a result, a decrease in plant immunity.
5. Incorrect top dressing. In particular, an excess of nitrogen in the soil makes cucumbers an easy "catch" for infections, however, and the lack of this element leads to weakening of the bush, which again increases the likelihood of infection.
6. Genetic characteristics of the plant. Different varieties and hybrids of cucumbers are not equally susceptible to various diseases, and therefore, they can feel differently on the same bed. In addition to variety, the quality of the seed material also affects the state of plant immunity. So, many pathogens of cucumber diseases, including those causing white plaque on leaves or fruits, have the ability to maintain viability in seeds for a long time. After these seeds germinate, the disease is activated.

Did you know? The longest cucumber in the world was grown in 2008 by a Briton named Alf Cobb - the length of the vegetable was 91.7 cm.

Diagnosis and treatment of white plaque diseases

White coating on greenhouse cucumbers often causes fungal diseases, namely:

• powdery mildew;
• white rot;
• downy mildew.

Powdery mildew

The causative agent of the infection, common not only among cucumbers, but also among all representatives of pumpkin, is the marsupial fungus Oidium erysiphoides Fr. In the southern regions, two other fungi sometimes cause the same symptoms on cucumbers - Sphaerotheca fuliginea Poll f. cucurbitae Jacz. and Erysiphe polygoni D.C.

Powdery mildew often affects cucumbers growing in the open ground, however, the disease can occur in greenhouses, more often, infection begins from those plants that are located closer to the doors or windows of the greenhouse.The likelihood of developing an infection increases with a combination of such factors:

• high humidity + relatively cool air (from + 16 ° С to + 20 ° С);
• low humidity + excess light.

The direct cause of the disease can be the physical presence of the pathogen in the soil, which is facilitated by growing cucumbers in one place for several years or ignoring weeding (powdery mildew pathogen winters on some perennial weeds, for example, plantain).

Important! The peak of infection occurs in the middle of summer, which is associated with the features of the life cycle of the pathogen fungi.

Powdery mildew can be distinguished from other fungal infections by the following signs:

• characteristic white coating on the inner side of the leaf plate, stem and petioles;
• light spots on the outer side of the sheet, arising as single, but very quickly merging into a single whole;
• leaf deformation (the surface of the plate becomes wavy, then bends and dries);
• the bush looks dehydrated;
• the fruits are poorly developed and have a bitter taste and a soft, sluggish structure.

If untreated, the bush gradually dries and dies.To combat the pathogen at an early stage, biological preparations have shown high efficiency:

• "Pseudobacterin-2";
• "Bactofit";
• "Gamair";
• Planriz.

To stimulate the plant’s own reserves for the fight against fungus, some farmers use non-toxic general strengthening agents such as Novosil or Immunocytophyte. If such measures do not give a result, you have to resort to the use of systemic fungicides.

Did you know? According to the US Environmental Protection Agency, pesticides provoke the development of malignant tumors. Among insecticides and herbicides, this danger is fraught with 30 and 60%, respectively, and among fungicides - no less than 90%!

White rot

The disease causes the fungus Sclerotinia sclerotiorum, which awakens with a combination of high humidity and cool air. Often affects cucumbers growing in heated greenhouses, where it receives an additional incentive for development in winter.The spread of infection is also facilitated by thickened planting and the close proximity of other crops also susceptible to infection. The fungus persists in the soil, but the lesion occurs through mechanical damage that occurs, for example, in the process of improper removal of stepsons.

In the future, the infection spreads very quickly, and the only way to stop this process is to immediately remove the affected parts of the plant.

Symptoms of white rot:

• a white coating, similar to flakes, appearing on the aerial parts of the bush and rapidly growing into large spots;
• softening and decay of the affected areas (infected fruits seem to be moldy);
• withering of individual lashes due to a violation of water metabolism;
• as the disease develops, the foci of infection darken and become dense.

For the treatment of the disease, Sumumlex or Rovral preparations are used. They must be mixed with water to the consistency of the slurry and treated with this tool the stems of the affected plants. In the later stages, the beds are treated with fungicides containing copper - “Ordan”, “KhOM”, “Abiga-Peak”, “Proton-Extra”.

False dew

The scientific name for the disease is peronosporosis. Its causative agent is the fungus Pseudoperonospora cubensis Rostowz from the oomycete class. For greenhouse cucumbers, the disease is no less dangerous than for plants grown in open ground.

Like powdery mildew, peronosporosis most actively develops in mid-summer, but in regions with a warm climate, the epidemic may begin earlier.With weak immunity, the plant dies 10-15 days after the onset of the first symptoms, namely:

• gray plaque on the back of the sheet plate;
• light or yellow spots of an oily structure on the front side of the sheet (spots have the shape of a circle or polygon, gradually increase in size and merge with each other);
• the darkening of the sheet plate and the acquisition by it of a characteristic brittleness, so strong that over time the sheet crumbles in parts to the very stalk under the influence of wind.

Peronosporosis is called downy mildew due to the similarity of the symptoms of these diseases.

You can distinguish them if you look closely at the color, shape and structure of the spots on the leaves:

Modern biologics and immunostimulants are used to treat peronosporosis. In addition to the aforementioned Gamair, Biktofita, Pseudobacterin-2, Planriza, Immunocytophyte and Novosil, this list can be supplemented with such means as Fitosporin-M, Trichodermin or Vitaplan.

An alternative is the use of more "heavy" fungicidal drugs.

How to deal with white plaque?

If the stems, leaves or fruits of greenhouse cucumbers are covered with white coating, there are two ways to deal with this problem - using modern pesticidal preparations or more gentle and usually environmentally friendly folk remedies.

Did you know? Studies conducted by Harvard University graduate school public health experts have shown sad statistics: work related to pesticides increases the risk of developing Parkinson’s disease in its executor by 70%.

The specific choice of the line of behavior depends on the farmer’s personal preferences, his financial capabilities, the particular disease and the degree of his neglect.

Chemicals for fighting

Since the diseases of cucumbers mentioned above are fungal in nature, fungicides are used to treat affected plants. Some agents, in addition to the fungicidal effect, also have insecticidal and / or acaricidal activity (effective against harmful insects and ticks), thus, processing can solve several problems simultaneously.The list of modern fungicidal preparations is wide. Among the drugs most often used to combat powdery mildew, white rot and peronosporosis, we can name the following:

• "Azocene";
• "Acrobat MC";
• Bayleton;
• "Quadrice";
• Cumulus
• "Kuproksat";
• "Privent";
• "Ridomil Gold";
• "Saprol";
• "Speed";
• "Gates";
• Tiovit Jet;
• "Topaz";
• "Topsin";
• "Fundazit";
• "Fundazole".

Important! Use these drugs should be strictly in accordance with the instructions, paying attention to how long after processing the cucumbers can be used as food.

In the process of spraying, it is necessary to carefully process the lower part of the leaves, and also not to forget about the surface of the soil around the bush, where most of the pathogen is concentrated.

Folk ways

Among the popular ways to combat white plaque on cucumbers, the following are popular:

1. Soapy soda solution. Finely grated laundry soap and baking soda are mixed with water in a ratio of 1: 1: 20. The finished preparation is sprayed with the affected bushes. After a week, the procedure is repeated.
2. Soap solution of copper sulfate. Liquid soap is added to the water in a ratio of 10: 1, as well as copper sulfate at the rate of 7 g per 10 l of solution. Mix thoroughly and spray the beds.
3. Potassium permanganate solution (2 g per 10 l of water). Used for foliar treatment.
4. A mixture of wood ash, ground chalk and copper sulphate. Chalk and ash are mixed in equal parts, after which copper sulfate is added to the resulting composition at the rate of 1 tsp. per 500 ml of the working mixture. This powder is sprinkled on the leaves and stems of the affected plants.
5. Milk serum. The liquid is mixed with water at a ratio of 3:10, copper sulfate is added to the finished solution at the rate of 1 hour per 10 liters and the bushes are immediately sprayed.
6. Horsetail decoction. Dry or fresh grass is poured with water (in the first case, the ratio is 1: 100, in the second - 1:10) and insist day. Then they are decanted, put on fire and evaporated for 2 hours. The cooled broth is diluted with water in a ratio of 1: 5 before use. Used to spray the beds.
7. Infusion of marigolds. Finely chopped plants, along with flowers, are poured with water in a 1: 1 ratio. They insist for two days, decanted, add 20 g of grated laundry soap and spray the cucumbers with the obtained product.
8. Dung infusion. Mullein is mixed with water in a ratio of 1: 3, insisted for 3 days, bred with 2 parts of water, filtered and treated the aerial part of the plants.
9. A decoction of garlic. 75 g of chopped garlic are added to 1 liter of water (you can use either the cloves or the stem), bring to a boil, let cool and decant. Bring the amount of solution to 10 l and use for spraying.
10. Milk solution with iodine. Low-fat cow's milk is diluted with water in a ratio of 1: 9. An iodine alcohol solution (about 10 drops per bucket) is added to the resulting mixture and immediately treated with the resulting plant preparation.
11. Wood ash. 500-600 ml of crushed ash is poured into 3 liters of boiling water, allowed to cool, 7 liters of water are added and used as a means for spraying cucumbers.

Did you know? You won’t surprise anyone with square watermelons today, but few have heard that cucumbers can have such a shape. Meanwhile, such a miracle of agricultural technology is gaining popularity in the United Arab Emirates.

Prevention of white plaque

Diseases that cause a white coating on the leaves and fruits of cucumbers are treated with varying degrees of difficulty: if some problems are easy to get rid of, then others are deadly for the plant, and sometimes even require the introduction of a long quarantine throughout the site. However, in both cases, the farmer’s losses will be much less if measures are taken in advance that reduce the risk of plant infection in the garden to a minimum. To do this, you must adhere to the following standard rules:

1. Responsibly approach the selection of cucumber varieties. Many modern hybrids have genetic immunity to most dangerous diseases, choosing them for planting, you can significantly save on the costs of prevention and treatment of plants.
2. Use only quality seed. - Do not try to grow seedlings from seeds obtained from weak or diseased plants. In all cases, except for the purchase of expensive seeds from leading European brands (the manufacturer of such a product carries out its full pre-planting treatment), perform a full range of reinforcing and disinfecting measures before sowing.
3. Follow established crop rotation rules. When planting the same or related crops in one place for several years in a row, the probability of plant damage by their characteristic diseases and pests increases many times. In addition, the soil on such beds loses exactly those nutrients that are needed for a particular culture.
4. Avoid thickening of the landing. The presence of sufficient space is a prerequisite for the development of the bush, providing it with full access to sunlight and nutrients in the soil, as well as the necessary ventilation.
5. Thoroughly disinfect the working tool before starting any garden work.
6. Weed beds regularly. Weeds, along with insects and birds, are the main "suppliers" of pathogenic microflora, which causes the most dangerous infectious diseases of garden crops. For this reason, it is recommended to remove such plants not only from the greenhouse itself, but also from the territory adjacent to it.
7. Conduct planned preventive treatment of greenhouse plants from pests. It is advisable to use biological insecticides and acaricides in this case - they are not dangerous to humans and do not harm the environment.
8. Ensure a stable microclimate in the greenhouse, avoiding overheating and waterlogging of the air. It is also important to organize an automated ventilation system inside the greenhouse, and if this is not possible, ventilate it regularly.
9. Prevent soil depletion in the greenhouse, timely make organic and mineral fertilizers according to the scheme recommended for growing cucumbers.
10. Water cucumbers only at the root (especially during the day), always using soft and warm water.
11. If foci of infection are identified on the bed, immediately remove the problem fragments (leaves, fruits), and in the case of infections that cannot be treated (for example, the tobacco mosaic virus) - remove the entire plant.
12. Do not leave any plant debris on the bed after full harvestif possible, planting green manure on the vacated area. It is also recommended that in the fall, bookmark future biopreparations for the prevention of fungal and bacterial infections, as well as against pests wintering in the soil.

Healthy cucumbers should have a beautiful green color. The presence of white plaque on the stem, leaves and, especially, on the gherkins is evidence that the plant is infected. It is dangerous to eat such fruits, so it is important to detect and stop the problem in time, and even better to organize care for the garden in such a way that there are no prerequisites for its occurrence.