7 main reasons for white plaque on cucumbers and leaves
Almost every gardener has to deal with a white coating on the leaves of cucumbers, their stems or fruits. The pathology is mainly fungal in nature - plant tissues are infected by fungi, causing the appearance of whitish, yellow and gray pubescent plaque. Let's figure out why a white coating appears on cucumbers, how dangerous it is, and whether powerful chemicals are always needed to get rid of it.
Causes of white plaque on leaves, stems and cucumbers
Cucumber is one of the most popular vegetable crops among gardeners. But often when growing, you have to deal with troubles in the form of a white coating on the stems, leaves and fruits. The reasons for this phenomenon lie in:
- sudden changes in average daily temperature;
- prolonged rains;
- watering with cool water;
- dense planting;
- high humidity in the greenhouse;
- violation of the rules of agricultural technology (weeding, loosening);
- lack of sunlight;
- excess nitrogen in the soil;
- lack of phosphorus and potassium.
Such disturbances in crop cultivation lead to the development of fungal diseases and the spread of insect pests.
Diseases and pests that cause white plaque
Diseases, causing the appearance of a whitish or yellow coating on the leaves of cucumbers, are mainly of a fungal nature (powdery mildew, peronosporosis, white rot, ascochyta). White mosaic refers to viral diseases.
Spider mites that feed on plant tissue also cause white spots to appear on leaves - the result of impaired photosynthesis in damaged areas.
Powdery mildew
Powdery mildew (ashtray, white) - a fungal disease that occurs when a plant is infected with ectoparasites. At the end of May - beginning of June, whitish mycelium begins to develop on young shoots and leaves. Small drops of sticky, cloudy dew appear on the plants.
The pathogen overwinters in the upper layers of the soil, on plant debris, and with the onset of spring it spreads from the lower leaves up the stems.
Signs:
- whitish coating on leaves and stems;
- brown balls inside plaque;
- drops of dew on the leaves;
- dry, curled leaves;
- rot on the fruit.
Without treatment, the plaque thickens, turns brown and spreads throughout the plant. The cucumbers look like they are covered in mold. These symptoms indicate the last stage of the disease. Treatment in this case is pointless.
The photo shows powdery mildew.
The table presents effective folk methods of combating powdery mildew.
| Recipe | Application |
| 10 liters of water, 1 liter of yogurt, kefir, whey. | Daily treatment of plantings is allowed until the disease is completely eliminated. |
| 1 liter of water, 0.3 tsp. soda ash, 25 ml of liquid soap. | Treat the plantings once every 7 days. |
| Leave 1 liter of wood ash in 5 liters of boiling water for 24 hours. | Treat bushes once every 7 days. |
| Mullein infusion 1:10, leave for 3 days | Water at the roots in the evening every 7 days. |
| Infuse 100 g of dried horsetail in 10 liters of water for 24 hours, then boil over low heat for 2 hours, strain and cool. Dilute with water 1:5. | Treat bushes once every 7 days. |
| Pour 0.5 buckets of marigold inflorescences with warm water, leave for two days, add 50 g of soap shavings. | Treat plants twice a week. |
Effective chemicals:
| Name | Application | Toxicity |
| "Topaz" | Dissolve 2 ml in 10 liters of water and add another 10 liters. Carry out the first treatment after the appearance of 8-10 true leaves, the second - at the beginning of flowering, 10 days after the first. | Not phytotoxic, not dangerous for birds, fish, beneficial insects and humans. |
| "Fundazol" | Dissolve 10 g in 10 liters of water. Carry out the treatment at least three times, every 10 days. | Moderately toxic to insects and humans. |
| "HOM" | Dissolve 40 g of powder in 10 liters of water, add 100 ml of skim milk. Spray once a week in the evening. | Not phytotoxic, not dangerous for birds, fish, beneficial insects and humans. |
| "Skor" | Dissolve 2 ml in 10 liters of water, treat three times with an interval of 10-12 days. | Not phytotoxic, not dangerous for birds, fish, beneficial insects and humans. |
| "Tiovit Jet" | Dissolve 30 g in 10 liters of water. Treat bushes 2-3 times per season. | Not phytotoxic, not dangerous for birds, fish, beneficial insects and humans. |
Downy mildew (downy mildew)
Downy mildew, or downy mildew, appears as white-yellow oil spots on the leaves of cucumbers. As the disease progresses, the back side of the leaves becomes covered with a purple coating. The spots gradually increase in size and merge. The leaves wrinkle, dry out and die. Without treatment, peronosporosis can completely destroy cucumber plantings.
Reference. Downy mildew appears only under favorable conditions for it - prolonged rains, watering with cold water, excess moisture in the soil.
Folk remedies against peronosporosis:
| Recipe | Application |
| 5 liters of water, 40 g of soda, 50 g of soap shavings. | Spray the soil and plants 4 times per season with an interval of 7 days. |
| 1 liter of skim milk, 40 drops of iodine, 25 g of liquid soap. | Spray cucumbers regularly throughout the growing season at intervals of 10 days. |
| Bring 0.5 kg of onion peel and 10 liters of water to a boil and leave for 5-7 days. | Treat 3-5 times a month until symptoms disappear. |
The table describes chemical agents against downy mildew.
| Name | Application | Toxicity |
| "Acrobat MC" | Dissolve 50 g in 10 liters of water. Carry out the treatment at the first signs of illness, repeat after 2 weeks. | Non-toxic to birds, fish and humans. |
| "Alirin B" | 2 tables dissolve in 10 liters of water - for watering under the bush.
1 table per 1 liter of water - for spraying plants. The frequency of treatments is 2-3 times per season. |
|
| "Oxyhom" | 30 g per 10 liters of water. Spray the plants in the evening. The frequency of treatments is 3 times per season with an interval of 15 days. | |
| "Ordan" | 25 g per 10 liters of water. Apply treatment at the first signs of illness, repeat after 2 weeks. |
White rot (sclerotinia)
Causative agent of white rot - marsupial fungus sclerotinia. The spores penetrate plant tissue and provoke the development of mycelium. As a result, a cotton-like white coating appears on cucumbers, stems and leaves. The affected areas become watery, the tips of the shoots and leaves wither and die.
The table contains effective folk remedies.
| Recipe | Application |
| 1 liter of milk, 1 tbsp. l. shavings of laundry soap, 30 drops of iodine, 10 liters of water. | Treat bushes generously 3-4 times a week. |
| 10 liters of water, 8 tbsp. l., 4 tsp. potassium permanganate, 1 tbsp. l. soap shavings. | Treat plantings once every 7 days. |
| Mix wood ash and crushed chalk 1:1, add water to obtain a thick porridge. | Cut off the affected leaves and stems and coat the cut area with the resulting mixture. |
Chemicals to combat white rot:
| Name | Application | Toxicity |
| "Abiga Peak" | 50 ml per 10 liters of water. Treat plants 3 times within 20 days. | Non-toxic to humans and the environment. |
| "Acrobat MC" | 20 g per 5 liters of water. Carry out the treatment 2 times with an interval of 10 days. | |
| "Ridomil Gold" | 25 g per 10 liters of water. Treat plants 3 times every 7 days. |
Gray rot
Gray rot - a disease caused by the fungus Botrytis cinerea. As the disease progresses, a whitish coating with a gray tint appears on the fruits, leaves and stems. Affected areas rot and die. Cucumbers become watery inside and become covered with a gray fluffy coating.
Folk remedies are effective only at the first signs of the disease. They are also used for preventive treatments.
| Recipe | Application |
| 50 g of soda ash, 80 g of copper sulfate, 50 g of soap shavings per 10 liters of water. | Treat bushes 3 times a week. |
| 2 tsp. brilliant greens, 1.5 tsp. potassium permanganate, 25 ml of liquid soap per 10 liters of water. | Treat plants 2-3 times a week. |
| 10 g of boric acid, 1.5 g of potassium permanganate, 30 ml of iodine, 50 g of soap shavings per 10 liters of water. | Treat plantings 3-4 times a week. |
The table shows popular chemicals against gray rot:
| Name | Application | Toxicity |
| "HOM" | Dissolve 40 g of powder in 10 liters of water, add 100 ml of skim milk. Spray once a week in the evening. | Non-toxic to humans and insects. |
| "Rovral" | The powder is mixed with lime or chalk in a ratio of 1:1 or 2:1 and coated with infected stems 3 times a month. | |
| "Euparen Multi" | A 0.2% solution is used to treat bushes once every 14 days. |
White mosaic
White mosaic is a viral disease. Signs develop according to the following scheme:
- highlighting areas along the veins;
- spots in the form of stars and yellow rings;
- proliferation of white spots with a yellowish tint on foliage and fruits.
There are no effective treatments for the viral disease. Sick plants are completely removed from the site and burned.
Ascochyta blight
Ascochyta blight - a dangerous fungal disease that causes the gradual death of the bush. The spread of the fungus begins from the stem, without affecting the leaves, so the plant remains viable for some time. Leaves are affected at the beginning of the fruiting period.
Signs:
- vague spots on the edges of the leaf blade are brown and then whitish with a yellow tint;
- raised areas on spots with spores inside;
- drying and dying of leaves.
What to do if the cucumbers are covered with a white coating? The fungus that causes ascochyta blight is unable to reproduce in soil. The pathogen is found on cucumber seeds. Therefore, the main measure to prevent the disease is pre-sowing disinfection of seed material with fungicides.
The table shows preparations for treating cucumber seeds before sowing.
| Name | Application |
| "Baksis" | Soak the seeds for 2 hours in 0.2% suspension. |
| "Planriz" | Soak the seeds for 6 hours in a 1% solution. |
| "Fitosporin-M" | Soak the seeds for 2 hours in the working solution. |
There are no folk remedies to combat ascochyta blight.
Spider mite
Spider mites feed on plant tissue. It affects cucumber plantings in open and closed ground.
The main sign of its presence is small white dots on the back of the leaves. Later, a thin cobweb envelops the foliage.
With severe damage, the leaves turn white from numerous damages.Hordes of spider mites are noticeable on the stems.
Chemicals are used in extreme cases when traditional methods have failed. Insecticides quickly kill pests, but they are toxic to humans and the environment. Another disadvantage of such treatments is the rapid development of resistance in insects. Therefore, it is recommended to change the preparations every 2-3 sprayings.
Spraying is carried out in the evening to prevent sunburn on the leaves.
The table shows effective insecticides. Treatment with chemicals is stopped 20 days before the start of harvest.
| Name | Application | Protection period | Treatment frequency |
| "Plant-pin" | The drug is produced in the form of sticks, which are immersed in the ground next to the bushes. | 1.5 months | 1 |
| "Karbofos" | 70 g per 10 liters of water, consumption - 0.5 liters per bush. | 7 days | 2 |
| "Flumite" | 5 ml per 10 liters of water, consumption - 1 liter per plant. | 30 days | 1 |
| "Aktellik" | Suspension with a high toxicity class. It is considered the best drug for spider mites.
2 ml are diluted in 2 liters of water and used immediately. Consumption - 2 liters per 10 sq. m. |
10-12 days | 2 |
The table contains folk remedies for pest control.
| Recipe | Application |
| Pour 0.5 buckets of potato tops with water, leave for 5-7 hours, add 50 g of soap shavings. | Spray the plantings once a week. |
| Infuse 30 g of dandelion roots in 1 liter of water for 5 hours. | Process cucumbers 2 times a week. |
| Infuse 1 kg of hogweed in 10 liters of water for 24 hours. | Treat plantings once a week. |
| Infuse 2 heads of garlic in 1 liter of water for a week, dilute with water 1:2 before use. | Spray the bushes 1-2 times a week. |
| Infuse 100 g of datura in 1 liter of water for 10-12 hours. | Spray cucumbers once a week. |
| Infuse 100 g of dry creeping mustard in 1 liter of water for 12 hours, dilute with water 1:2 before use. | Treat bushes once every 7-10 days. |
Prevention
Measures to prevent white plaque on cucumbers:
- Timely removal of weeds and plant residues.
- Maintaining crop rotation. Cucumbers are best planted after cabbage, legumes, corn, onions, and garlic.
- Pre-planting treatment of the site with biological products “Alirin-B” and “Gamair”.
- Disinfection of holes with a hot solution of potassium permanganate.
- Control of nitrogen content in the soil.
- Planting varieties and hybrids of cucumbers resistant to fungal diseases.
- Sparse planting of seedlings.
- Preventive treatment of plantings with “Fitosporin”, “Kuprolux”, “Ordan”.
- Select a site in a sunny, draft-free location.
- Fertilization with potassium and phosphorus.
- Sprinkling instead of watering from above to prevent water retention on the foliage.
- Frequent loosening of the beds.
- Disinfection of greenhouses with sulfur bombs.
- Humidity control in the greenhouse (above 80-85%).
- Air temperature control (optimally - +25...+27°C).
- Replacement of the top layer of soil.
Conclusion
The white coating on cucumbers appears due to fungi that cause powdery mildew, downy mildew, ascochyta blight, gray and white rot. The chemical preparations “HOM”, “Oxychom”, “Ridomil Gold”, “Acrobat MC”, “Alirin B”, “Ordan” are effective against them. Folk remedies based on onion peels, tobacco dust, soda ash, milk, fermented milk products, iodine, brilliant green, marigolds, and yarrow are effective at the early stages of disease development and prevention.
There are no drugs against viral white mosaic. It is important to follow the rules of agricultural technology to prevent infection.
To combat spider mites, the insecticides Actellik, Karbofos, Plant-pin, and Flumite are used. Folk remedies are used as auxiliary methods of pest control.