Why do cucumber leaves turn white? What to do and how to prevent it.

Sometimes, when growing cucumbers, vegetable growers notice white spots appearing on the leaves. Foliage color can change on cucumbers planted in a greenhouse, hotbed, or unprotected beds. Improper care is often the cause of this whitening. Sometimes, the problem arises from a nutrient deficiency or disease. Whitening is also highly likely after exposure to cold.

Causes of cucumber leaf whitening

It's not always possible to definitively determine the cause of whitening cucumber leaves when grown in a greenhouse or open ground. Color changes are caused by adverse environmental factors or pathogenic microorganisms. To accurately identify the cause of the light spots, consider the accompanying symptoms.

There are two groups of factors that cause cucumber leaves to turn white and dry out:

1. Failure to comply with agricultural practices, errors in irrigation and soil preparation before planting, and failure to fertilize often cause the appearance of white spots.
2. Diseases and pests damage the surface of the leaf blades. They become thinner and covered with characteristic spots. Other signs of infection also appear.

Deciding what to do with cucumbers with white leaves requires accurately determining the cause. There's no universal solution for this problem. For example, if light spots appear as a result of disease, folk remedies and fungicidal preparations can be used. If cold weather is to blame, cover the plants with plastic wrap or other covering material.

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Care mistakes

This heat-loving vegetable requires specific conditions for proper growth. Therefore, problems often begin immediately after planting cucumber seedlings in the ground. Sometimes, a lack of sunlight can cause leaf whitening. This condition is especially common in greenhouse-grown plants. Leaf whitening is much less common in open beds. Lower leaves are usually the first to suffer. If there is no other damage, no special measures are needed.

Similar changes occur when there is a lack of useful elements:

• deficiency of potassium and magnesium causes the leaves of the lower tier to turn white;
• with a lack of iron and manganese, a white coating is formed in combination with dark veins;
• Due to insufficient copper, the upper shoots are the first to wither.

Such problems can be eliminated by applying the necessary fertilizer. Young plants typically suffer from nutrient deficiency. After harvest, foliar discoloration is a natural part of the plant's decline.

Landing time

Cucumbers thrive in warm climates. Cold is harmful to them. Therefore, when determining the planting time, consider the climate in the growing region. In central Russia, cucumber seedlings can be planted in a greenhouse or hotbed in early May or late April. It's best not to rush planting outdoors. If the weather forecast predicts cold snaps or frost, transplanting should be postponed until the weather warms up.

Watering

Timely irrigation is essential for proper vegetable development. Sometimes a lack of moisture or an excess of it can cause cucumber leaves to turn white. This usually occurs when growing plants in open beds, as it's more difficult to control moisture levels there.

In some regions of the country, excessive rainfall occurs during the summer. Increased soil and air humidity cause whitish spots to appear on cucumber leaves. Due to the excess moisture, the root system cannot properly aerate and begins to rot. This leads to the foliage turning white and the gradual death of the plant.

A lack of water also negatively impacts the health of cucumber plants. Due to a lack of moisture, leaves become lighter at the edges and dry out. Therefore, it's important to carefully monitor the plants. The soil under the cucumbers should be moist, but not wet or dry.

Soil acidity

High acidity often causes cucumber leaves to turn white at the edges. This type of soil is unsuitable for growing cucumbers, which causes the plants to stop growing. To rule this out, a soil acidity assessment is performed.

To normalize the soil's condition, deoxidize it. To do this, add wood ash, dolomite flour, or crushed chalk. It's best to do this in advance, before transplanting the seedlings to their permanent location.

Diseases and pests

If all gardening practices have been followed, but cucumber leaves continue to turn white, wilt, and dry out, disease or pest infestation may be the cause. Detecting insect activity is easy. Just carefully inspect the bushes, especially the undersides of the leaves. This is where pests prefer to hide. To diagnose diseases, pay attention to additional signs: rot, an unpleasant odor, and a coating on the plant's surface.

Powdery mildew

This fungal disease most often causes the tips of leaves and their entire surface to turn white. High humidity and low temperatures favor the development of powdery mildew. Initially, a white, powdery coating appears on the leaves. Signs of infection then spread to the trunk and fruit. The disease inhibits photosynthesis. Therefore, if left untreated, the plant dies.

Powdery mildew can be treated with the following remedies:

1. Spray the bushes with a solution of 7 liters of water and 3 liters of whey. Lactic acid bacteria destroy the pathogen and improve yields. You can also add 1 cup of granulated sugar to the solution to make the treatment more effective.
2. Fresh manure is poured into water and left for three days. The liquid is then filtered and diluted with clean water at a ratio of 1:10. The resulting solution is then applied to the infected bushes.
3. For severe powdery mildew infestations, treatment with Topaz, Jet, Hom, and KE is effective. In open beds, plants can be sprayed with a 20% colloidal sulfur solution. This can be used for greenhouse plants by increasing the concentration to 40%.

Ascochytosis

Another type of fungal infection causes leaf whitening in cucumber seedlings and mature plants. Symptoms typically develop at the tips of the leaf blades, but less commonly, they can spread throughout the entire surface. As the disease progresses, the foliage turns a dirty gray and then dries up. Fruit that has already formed by this time shrivels.

To combat ascochytosis, preventative measures are effective:

• plants are watered only with warm water;
• do not allow temperature fluctuations inside the greenhouse;
• Before use, the soil for growing seedlings is steamed or watered with a solution of potassium permanganate;
• Plants are regularly sprayed with Bordeaux mixture at a concentration of 1%, a solution of copper sulfate or urea.

Anthracnose

This fungal disease is promoted by nutrient deficiencies and damp, stale air in the greenhouse. Anthracnose causes white spots to appear on the leaves of newly planted plants and darkening of the tips. The affected plants then dry out. Cankers often form on the leaves of cucumber plants affected by anthracnose.

The following remedies are used to treat anthracnose:

• watering plants at the roots with a solution of the drug "Abiga-Pika" with a concentration of 0.5% or one percent Bordeaux mixture;
• spraying leaves with the drug "Poliram" or copper oxychloride;
• Infected bushes can be treated with Quadris, Kumus or Strobi.

White rot

This fungal disease causes the leaves of seedlings to turn white after being planted in a greenhouse. It is caused by a sudden drop in room temperature or drafts. Lack of ventilation is also a contributing factor. To prevent white rot, plant seedlings at a distance from each other, avoiding overcrowding.

Signs of white rot infection include:

• wet spots on the surface of cucumbers;
• growths resembling white cotton wool at the site of injury;
• mucus-like discharge.

Fungal spores enter plants through contaminated soil or untreated equipment. They enter the plant through damaged tissue. White rot cannot be cured. Therefore, infected plants are destroyed, and the soil is doused with boiling water or treated with steam.

White mosaic

The disease is a viral infection. The pathogenic virus enters plant tissue through damaged areas of the plant, gradually moving toward the root system. The disease can be recognized by the appearance of white spots with a yellowish tint on the surface of the leaves. Infected plants experience stunted growth, and the fruits become deformed and have an unpleasant taste.

Spider mite

These tiny parasites settle on the undersides of leaf blades and suck out their juices. The damage impairs photosynthesis and weakens the plant's immune defenses. These pests often coexist with gray mold, which develops on the lower parts of stems and leaves. Spider mite infestations can be recognized by white-yellow spots on the undersides of leaves and stunted growth of young plants. High temperatures and dry air are favorable conditions for the pest's emergence.

Methods of control:

1. If spider mite If a few plants are infected, they are treated with a solution of laundry soap. Strong-smelling marigolds, mint, and onions can be planted between the rows. These plants repel pests.
2. You can quickly and safely eliminate the pest by introducing the Phytoseiulus mite to your plants. It feeds on the parasite's egg masses. This is done every 20 days.
3. For severe spider mite infestations, use Bitoxibacillin or Karbofos. Apply in the evening to allow the treatment to take effect overnight.

Whitefly

Whiteflies typically infest greenhouses, but under favorable conditions they can also infest cucumbers grown in open beds. Adults are 1.5 mm long and are flying insects with light-colored wings. They form large colonies and settle on the undersides of leaves. When an infected plant is touched, a swarm of tiny white flies rises into the air.

The insects feed on cucumber sap. To extract it, they pierce the surface of the leaves. This causes light spots to form in the damaged areas. The leaf gradually dries up and falls off. As they feed, the whiteflies secrete a sugary substance that promotes infection.

You can destroy whiteflies using the following means:

1. Pests are collected mechanically. To do this, make sticky traps from a sheet of cardboard and sticky bait and place them near infested plants.
2. To physically kill whiteflies, the parasite Encarsia is used. It is introduced to the affected plants. Once all the whiteflies have been consumed, the Encarsia dies.
3. In cases of widespread whitefly infestation, plants are treated with insecticides. Products such as Aktara, Actellic, and others are effective.

White spot treatments

Quadris effectively treats plants for many diseases and prevents their recurrence. This systemic fungicide penetrates plant tissue and destroys pathogens. Prepare the working solution according to the instructions. Apply 100 to 200 ml per plant. During the growing season, apply the solution three times, spaced 3 to 5 weeks apart.

The product "Kuproksat" is suitable for treating plants in greenhouses or open garden beds. It prevents infestations of vegetables by insect pests and diseases. It is available as a ready-to-use liquid. "Kuproksat" is especially effective as a preventative measure. Therefore, it should be applied to the cotyledon leaves of seedlings before transplanting them to their permanent location.

If the cucumber cotyledons have turned lighter after sprouting, treat them with "Jet." This product is available commercially as a powder. Before use, dilute it with water according to the instructions at a rate of 100 g per 10 liters of water. Use the solution immediately, as it loses its properties during storage. Spray twice a month until harvest.

Folk remedies for leaf whitening

To protect cucumbers from many pests, use a decoction made from onion peels. Use 300 grams of onion peels per 5 liters of water. Bring the mixture to a boil over low heat and simmer for 30 minutes. Then leave it in a covered container to cool. After 12 hours, strain the liquid and dilute it with water at a ratio of 1:5. Spray the affected plants with this solution and water the soil beneath them.

Bread infusion is made from stale bread. The bread is crushed and covered with clean water. The mixture is left in a sealed container for 12 hours. Then, the bread pulp is squeezed out, 1 tablespoon of iodine is added to the liquid, and the mixture is diluted with 10 liters of clean water. The solution is sprayed on cucumber leaves every 15 days to maintain their natural green color.

Prevention

To avoid problems when growing cucumbers, it's recommended to use good seeds from regionalized varieties. It's best to buy them from reputable stores. Before sowing seedlings, be sure to treat the seeds and soil.

During the growing season, bushes are regularly inspected to detect the first signs of disease or pest infestation. Additionally, the bushes are sprayed with plant protection products. "Fitosporin-M" and "Obereg" are effective.

When growing in a greenhouse or hotbed, maintain a healthy microclimate. Regularly open the windows for ventilation and reduce humidity. Avoid sudden temperature changes or drafts.

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Bushes are watered early in the morning or in the evening, when the sun is not shining. Only warm water should be used for irrigation. It can be collected in barrels where it will settle and warm up during the day in the sun's rays. Water should be applied to the roots, being careful not to splash it on the leaves.

White spots on cucumber leaves appear as a result of disease, nutrient deficiencies, or poor agricultural practices. To save the plant, it's necessary to identify the cause of the changes and treat them.