Why white spots appeared on the leaves of cucumbers: reasons and what to do, how to deal with powdery mildew

Around the beginning or middle of summer, gardeners notice with alarm white spots on cucumber leaves. Most often this is a sign of a disease that threatens the plant. If you don't take action, you could lose your harvest.

Let's tell you why white spots appear on the leaves. Let's talk about what additional signs different diseases manifest and tell you how you can fight them at home.

Powdery mildew is the most likely cause

Powdery mildew is a common disease among garden crops and cucumbers are no exception. The disease manifests itself as a white coating. Most often, at the initial stage, it is localized along the edges of the leaf plate, then, if the gardener does not take action, the plaque covers the entire leaf. As the disease progresses, it affects all cucumber stems.

To a greater extent, the disease affects indoor crops - in greenhouses and hotbeds. However, under certain conditions, powdery mildew can spread to plants in open ground. The plaque is always only on the upper side of the sheet; nothing is noticeable on the lower side.

The causes of powdery mildew are:

• low air temperature against a background of high humidity;
• non-compliance with sowing schemes, due to which plants grow too close to each other;
• passion for nitrogenous fertilizers;
• excessive watering;
• uneven watering (if it’s dry, it’s swampy).

If powdery mildew is suspected, the affected leaves are torn off and burned. The plants in the greenhouse are provided with good ventilation and the water supply is reduced. The application of nitrogenous fertilizers is stopped.

The remaining cucumbers are sprayed with antifungal drugs. You can treat the bushes once every two weeks with Topaz solution (ampoule/10 liters of water), Tilt KE emulsion, Bayleton, Skor. If the white plaque has appeared recently, Bordeaux mixture will help.

If not only the leaves, but also the stems are covered with a white coating, I pull out the plant, take it outside the site and burn it. There is no use in treating him.

Useful tips from experienced farmers

Each farmer uses his secrets to obtain a rich harvest . Tips from experienced gardeners will help you grow healthy cucumbers:

1. From the beginning of July, it is recommended to treat cucumbers with onion peel. To prepare 10 liters of boiling water, take 0.7 liters of onion peels, bring to a boil and leave for 24 hours. Dilute the resulting mixture with water in a ratio of 1:4. Spray the plant with the solution and water it 2-3 times a month.
2. During the flowering period, water the cucumbers with a mixture prepared from 2 liters of whey and 150 g of sugar.
3. To eliminate pests during growth, use a solution of iodine and laundry soap. To do this, dilute 30 drops of iodine in 10 liters of water, add 20 g of laundry soap and, if desired, 1 liter of milk. Spray once every 10 days.

White leaf mosaic

Unlike powdery mildew, white mosaic is a viral disease that affects cabbage, tomatoes, cucumbers and other plants. The virus is transmitted through dry infected leaves and develops inside a healthy leaf, which leads to such changes in the color of the plate.

At the beginning of the disease, white spots appear near the veins and do not have clear boundaries. As the disease progresses, the spots spread over the entire surface of the leaf and then turn yellow. The growth of new shoots slows down and the cucumbers look weak. The fruits are formed in small quantities, the yield is significantly reduced.

The reasons for the white mosaic can be:

• incorrect planting pattern;
• changes in air temperature, due to which the cucumber’s immune system weakens;
• increased air temperature when growing in greenhouses and greenhouses.

Seedlings planted in a permanent place are more susceptible to cucumber mosaic. Mature plants become infected much less frequently.

Treatment of viral plant diseases is ineffective, and the same applies to white mosaic. Plants with signs of viral damage must be removed and burned. Particular attention is paid to ensuring that there are no fallen dry leaves left on the ground.

If white spots appear on individual leaves, they need to be removed. You can leave the plant, but inspect it regularly. Radical removal of the entire bush is advisable only if the white spots are widespread.

When growing cucumbers indoors, you need to monitor the temperature and follow planting patterns.

White spots are a sign of spider mites

If cucumbers are grown in open ground and small spots, usually round in shape, appear on the surface of the cucumber leaves, the cause may be the activity of spider mites. It settles on the underside of the leaf, where it begins to feed on the sap of the plant. If you notice white spots, turn the sheet over to the bottom side up. The spider mite weaves a web here (hence the name), it is impossible to see it in any other way.

Other symptoms of damage:

• the leaf blade becomes covered with yellow spots over time;
• the plant weakens;
• productivity decreases.

Cucumbers on such a plant will be small in size, often of a changed shape. In especially severe cases, the formed ovaries fall off, and then the bush itself dies.

You can destroy spider mites with a solution of the drug Fitoverm. It is diluted with water at the rate of 4 ml per 400 ml of water. Spray cucumbers twice, with an interval of 4 days. After processing, fruits should not be eaten for three days.

If the outside air temperature is above 25 °C, Fitoverm will not help: it acts more slowly than the spider mite reproduces. In such a situation, it is necessary to treat the plants with stronger drugs - chemical acaricides. These include Neoron, Antiklesch, Sunmite, Apollo. When working with them, be sure to follow the instructions for use.

Leaves affected by spider mites are torn off and burned.

Diagnosis of diseases

If you regularly carefully examine the plants, you can identify painful changes by their appearance and take immediate action.

Having noticed external changes in plants, it is necessary to take urgent action

Symptoms of diseases: leaves turn yellow, turn pale, turn white, etc. - table

Seedlings don't grow

This occurs as a result of root death caused by watering with cold water or too low a room temperature. Plants stop developing and die; it is impossible to save them. Only re-planting the seeds will help if the planting time has not yet been missed.

Seedlings stop growing and subsequently die

Yellowing of seedlings

Yellowing of seedlings can have several reasons.

• Lack of microelements. In nutritious soil the plant has bright green leaves. The situation can be corrected by applying fertilizers (Kemira-extra, Fitosporin).
• Lack of soil. In a small container, the roots become crowded, the leaves turn yellow.
• Overexposure of plants. You should not keep the seedlings indoors for too long; 21–29 days after sowing, they must be transplanted into the ground.
• Insufficient lighting. Identifying the cause is not difficult, since in this case the cotyledon leaves turn yellow. The plant is moved to a brighter place or artificial lighting is used. To help the plant cope with stress, the leaves are sprayed with Epin solution.
• Excess nitrogen fertilizers can also cause yellowing of the foliage.
• Hypothermia of heat-loving plants. If the soil temperature is below +17 °C, the castings turn yellow and the seedlings stop growing.
• Infections and parasites. Yellowing of cucumber leaves can occur due to the presence of powdery mildew, spider mites and fusarium.

The plant may respond to improper care by yellowing leaves.

The seedlings are withering

With infrequent watering and dry soil, seedlings wither. It is necessary to water the seedlings daily, keeping the soil moist.

Ascochyta blight - a disease of weak bushes

Ascochyta blight is a fungal disease that most often develops on weakened cucumber bushes. The disease is widespread in greenhouses; when grown in open ground, it is detected less frequently.

Signs of disease development:

1. At the initial stage, small white spots form along the edges of the leaf blades. Sometimes they may have a brown tint.
2. Gradually, the area of ​​the spots increases, they merge and cover the entire leaf.
3. Over time, the leaf dries out.
4. A discharge appears on the stems, sometimes yellowish or brown in color.
5. The fruits become covered with black dots and become soft, as if they were kept in boiling water.

The plant is most often affected during the fruiting period, when all efforts go directly to the harvest. It is impossible to save the cucumber bush; the fruits are not suitable for food. They are removed and burned.

Most often, the cause of ascochyta blight is a violation of crop rotation (fungal spores remain in the soil). A secondary cause is high humidity.

Sunburn of leaves

Burns are the most common cause not related to the action of fungi and viruses. Cucumber responds well to direct sunlight, but does not tolerate it when it is refracted through the glass of a greenhouse or in droplets of water. That is why it is advisable to water the cucumber at the root at sunset or early in the morning.

You can distinguish sunburn from the consequences of diseases and pest activity by the following signs:

• relatively few spots;
• the location of the spots is chaotic, over the entire surface of the leaf (in case of diseases, the lesion begins from the edge or in the area of ​​the veins);
• there is no cobweb on the bottom of the leaf;
• stems are not affected;
• plants do not lag behind in growth, productivity does not decrease.

Sunburn cannot be treated; severely affected leaves can be removed. In the future, you need to organize proper watering, and on especially hot days, provide shading for the cucumbers.

Before starting treatment with drugs, it is necessary to exclude sunburn.

Why do the leaves of cucumber seedlings turn white?

The main reasons for this phenomenon are:

• sunburn if the seedlings were taken out of the room into the scorching sun without preparation;
• various diseases;
• lack or excess of moisture;
• damage to the root system during planting.

As a rule, the causes differ little from other cases, but the first signs occur much earlier.

How to prevent white spots on cucumbers

If you study all the causes of diseases that lead to a change in the color of the leaf blade from green to white, you will notice two patterns. First, most often white spots appear on cucumbers grown in greenhouses and hothouses. The second pattern is that there is almost always a violation of agricultural technology.

Therefore, to prevent leaf damage, the following rules must be observed:

1. Maintain crop rotation - do not plant cucumbers in one place for several years in a row.
2. Choose varieties that are resistant to fungal diseases.
3. Monitor the air temperature in greenhouses. For cucumbers, too cold air is just as dangerous as heat. The plant's temperature requirements vary depending on the stage of development.
4. Mulch the ground. Fungal diseases most often appear when the soil cover is open.
5. Provide adequate ventilation in greenhouses and greenhouses.
6. Follow planting patterns and do not thicken them.
7. Carry out pre-sowing disinfection of seeds.

As a measure to prevent white spots on cucumbers grown in open ground, you can use green manure in the soil. To do this, rye or oats are grown a year before sowing cucumbers. These plants perfectly disinfect the soil.

In order not to lose plants and crops, when white spots first appear, you need to understand their causes and treat them with antiseptics. At the earliest stages of development of powdery mildew, white mosaic and ascochyta blight, spraying with Bordeaux mixture 3% gives a good result.

The more attentive you are to preventive measures, the less often cucumbers will get sick.

Prevention

It is always easier to prevent a disease than to fight it.

Compliance with crop cultivation technology and careful care are the key to plant health and future harvest:

1. You can't plant cucumbers too often.
2. The landing site should be sunny and bright.
3. Water moderately, avoiding overwatering; apply fertilizing without fanaticism.

The main thing is to carefully inspect your plantings. Changes noticed in time will indicate problems, which, if eliminated, will prevent the spread of the disease.