Why does a white coating appear on cucumbers in a greenhouse and how to deal with it

Healthy cucumber bushes have a beautiful green color. The appearance of a white coating on various above-ground parts of the bush indicates that the plant is affected by fungal diseases. The fruits of such a plant cannot be eaten.

To avoid problems, you must adhere to the rules of crop care. We'll talk about them in more detail below.

Causes of white plaque on greenhouse cucumbers

White plaque on the vegetative parts of cucumbers - a symptom of various fungal diseases. They occur if the plant is weakened and has low immunity. These problems appear when optimal conditions for growing crops are not met in the greenhouse:

1. In case of temperature violation. If the air temperature in the greenhouse drops to +15°C, the development of the bush slows down, and at +10°C it stops. When the temperature rises to +30°C, the plant’s forces are aimed at protecting against overheating. When the temperature deviates in any direction, the crop experiences stress and becomes less resistant to various infections and pest damage.
2. With uneven watering. When the soil dries out, the plant slows down its growth. Various rots form in waterlogged soil. These factors reduce the immunity of the culture.
3. Failure to comply with the proportions of introduced microelements. An excess of nitrogen makes the crop susceptible to infections.
4. Poor quality seed processing. Pathogenic fungi remain viable for a long time on untreated seeds, and become more active after planting in the ground.

Powdery mildew

Real powdery mildew — a disease of cucumbers caused by ectoparasitic fungi of the type eryphyseal, or powdery mildew, fungi. Mycelium in the form of a white coating resembling flour appears initially on the lower leaves, then spreads to all above-ground parts of the bush, and in advanced cases to the fruits.

After the mycelium spores mature, liquid droplets form - this determined the name of the disease “powdery mildew”. Favorable conditions for the development of the disease are high humidity at an air temperature of +18°C...+20°C, watering with cold water, poor ventilation, and an excess of nitrogen in the soil.

Attention! The bushes located near the windows and doors of the greenhouse are most susceptible to attack by pathogenic fungi.

Causes of the disease:

• undisinfected seed material;
• the presence of mealy fungi in untreated greenhouse soil;
• the presence of plant remains from last year's bushes.

At the onset of the disease, small areas of white plaque appear on the leaves.. The affected areas gradually merge into one, completely covering their surface. As a result, the leaves become deformed, dry out and fall off. The bush looks lifeless, stops bearing fruit, and gradually dies.

White rot

White rot (sclerotinia) – a disease caused by the fungus Sclerotinia sclerotiorum, affecting all parts of the plant. Its development is caused by high humidity and low air temperature in the greenhouse. The fungus persists in untreated soil and affects plants through various mechanical damage.

Symptom: white cotton wool spots. The affected areas become watery, rotten, and a characteristic smell of rot appears. On the cut of the stem, clusters of black fungal spores – sclerotia – are clearly visible. The disease quickly spreads to the entire plant, causing its death. To stop the infection process at the initial stage, the affected branches are removed.

Downy mildew

Downy mildew - downy mildew cucumbers The appearance of the disease is provoked by excessive moisture in the beds, watering the bushes with cold water, condensation in the greenhouse, poor ventilation.

Important! The fungus develops only in conditions of high humidity. Dry air has a detrimental effect on it.

Yellow or brown spots appear on the inside of leaves. After this, the outer part of the leaf blade is affected. A pale gray-violet coating appears on it. Almost immediately the leaves begin to turn yellow, dry out, and become brittle. The bush stops bearing fruit and fades. Cucumbers lose their taste. With weak immunity, the bush dies within two weeks.

A light gray fluffy coating in the form of mold appears on cucumbers when damaged gray rot. Brown spots form on the leaves and branches, the ovary and flowers acquire a brown tint. Gray mold causes rotting and the bush gradually dries out.

When a plant is affected by black rot (ascochyta blight) on the stems Watery, gray areas appear. Gradually they turn white and expand. The leaves turn brown, the fruits wither and gradually rot.

Plaque on cucumbers appears with a white mosaic. Small light areas are noticeable on the leaves, then they enlarge and darken, become hard, and curl. The bush stops growing and withers.

What to do and how to save the harvest

At the first signs of illness and timely treatment, they help traditional methods using products that are safe for health. For more serious damage, modern plant protection chemicals - pesticides - are used.

Chemicals

For fungal infections in the initial stages, biological products are used:

• «Fitosporin-M»;
• "Gamair";
• "Pseudobacterin-2";
• "Planzir";
• "Baktofit".

To stimulate the cultural defenses, many gardeners use growth stimulants:

• "Immunocytophyte";
• "Novosil".

If biological products do not give the expected result, fungicides are used:

• "Acrobat MC";
• "Quadris";
• "Kuproksat";
• "Skor";
• "Topaz";
• "Privant";
• "Bayleton";
• "Fundazol".

To destroy the pathogenic fungus, it is enough to prepare a 1% solution of these drugs.

Attention! Eating cucumbers is possible no earlier than 3 weeks after processing the bushes.

Treatment is carried out by spraying the entire bush. It is advisable that the solution gets on the ground around the plants. After treatment, the greenhouse room is ventilated. For small lesions, the drugs are diluted with water to a paste-like state and applied to the area with a white coating.

For severe lesions, copper-containing preparations are used:

• “HOM” - 30 g/10 l of water;
• “Ordan” - 35 ml/10 l of water;
• “Proton-Extra” - 30-40 ml/10 l of water;
• “Abiga-Pik” - 50 ml/10 l of water.

Traditional methods

In the fight against white bloom on cucumbers many farmers prefer safe traditional methods:

1. Baking soda and softened laundry soap are poured with water in a ratio of 1:1:20. After the soap has completely dissolved, the diseased plants are treated with the prepared composition.
2. To 10 liters of water add 1 liter of liquid soap, 6 g of copper sulfate.The composition is sprayed on the bushes.
3. A solution of potassium permanganate - 1 g/10 l of water - is sprayed on the bushes at the first signs of damage.
4. A dry mixture of 20 g of wood ash, 20 g of crushed chalk, 1 g of copper sulfate is used to dust the cucumber beds.
5. Kefir is mixed with water in a ratio of 3:10, 5 g of copper sulfate is added and the cucumber beds are sprayed.
6. Boil 50 g of garlic for 30 seconds. in 1 liter of water. The solution is cooled, filtered, mixed with 10 liters of water, and the diseased plants are treated.
7. The marigolds are crushed, filled with water (1:1), and left for three days. Add 25 g of grated laundry soap to the strained liquid. After the soap dissolves, spray the cucumbers.
8. Wood ash in the amount of 500 g is poured into 3 liters of boiling water, cooled, 7 liters of water are added, and the bushes are treated.

Prevention methods

Fungal diseases of cucumbers in a greenhouse can be prevented, if you follow the rules of agricultural technology:

1. Replace the top layer of soil in the greenhouse.
2. Before planting cucumbers, treat the area with the biopreparation “Gamair” and add wood ash.
3. For planting, choose varieties and hybrids that are resistant to crop diseases.
4. Treat the seeds with Fitosporin-M, a pink solution of potassium permanganate.
5. It is better to plant cucumbers if onions, garlic, legumes, and cabbage were previously grown in the greenhouse.
6. Maintain the microclimate in the greenhouse, ensure air circulation.
7. Thin out plants. In dense plantings, the roots do not receive enough nutrition, and air access to the plants is difficult.
8. Water the bushes at the root, without using cold water.
9. Timely fertilizing with phosphorus and potassium fertilizers.
10. Regularly loosen the beds.

Advice from experienced summer residents

Experienced summer residents recommend:

1. Carry out preventive treatments of the crop with Fitosporin-M and Ordan.
2. Before carrying out work, disinfect work equipment.
3. Remove leaves with a white coating immediately, without waiting for the disease to develop.
4. In the spring, before planting the crop, fumigate the inside of the greenhouse with sulfur bombs.

Conclusion

A white coating on cucumbers in a greenhouse is a sign of damage to the crop by various fungal diseases that can destroy a significant part of the crop. In order for plants to develop well and form high-quality fruits, they need careful care.

Knowing the symptoms of the disease, timely detection of fungal infections and correctly taken measures will help preserve the harvest.