Why do cucumber leaves turn yellow in a greenhouse and how to deal with it

Causes of yellowing leaves

Before starting to solve the problem, it is necessary to establish the cause of this phenomenon and review the rules for caring for plants. After all, if any disease develops, you need to act quickly so as not to lose the entire harvest.

The main factors that provoke the appearance of yellowness on the leaves:

• diseases and pests;
• insufficient lighting;
• unsuitable soil composition;
• violation of irrigation technology;
• poor pollination of bushes;
• temperature changes in the greenhouse;
• damage to the root system;
• sunburn;
• aging of foliage.

Planting density

If the plants are planted too densely, they become deficient in nutrients, which affects their appearance and can lead to the death of some bushes. The leaves begin to turn yellow and fall off.

The gardener needs to thin out the plants, remove some of the ovaries - no more than 25 inflorescences should remain on one vine. In this way, the normal development of the bushes is ensured, which guarantees a rich harvest.

Low air temperature

Cucumbers are heat-loving plants and are very susceptible to cold weather. If you ignore this rule and do not provide the plants with comfortable conditions, the consequences can be sad: yellow spots will appear on the leaves, which will gradually cover the entire leaf plate.

The problem can be eliminated using a special material (spunbond, agrotex), which must be used to cover the plants at night.

The leaf border or edge turns yellow

Yellowing of the leaf edge without the formation of yellow spots on the leaf blade itself indicates a lack of potassium.

Yellowing due to lack of microelements

What to do?

Feed the plant with potash fertilizers. It is best to use liquid preparations with a complex of useful elements.

Lack of moisture

Often the leaves of a crop in a greenhouse turn yellow due to non-compliance with watering rules. Cucumbers belong to the group of moisture-loving plants, which begin to get sick if there is a lack of moisture.

Too cold water is also not suitable for irrigation, since it causes the soil to cool, causing the leaf blades to turn yellow and the vines themselves to dry out. Cucumbers should be watered at the root, since water getting on the foliage can also lead to a change in color. The procedure is carried out in the absence of sunlight - late evening or early morning.

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Rules for caring for cucumbers if they turn yellow

If it was not possible to protect the cucumbers from yellowing, find the cause and eliminate it. After this, follow the agrotechnical rules:

1. Optimize your irrigation regime.
2. Monitor the temperature, not allowing it to drop below 15⁰C or exceed 30⁰C.
3. Remove excess bushes so that the planting does not look like a jungle.
4. Ventilate the greenhouse often.
5. Systematically apply foliar and root fertilizers.
6. Make sure that the destroyed fungus or pests do not return; if necessary, re-treat.

Remember that you need to support the immunity of cucumbers; foliar fertilizing with urea is ideal for these purposes.

Conclusion

Simple rules will help keep cucumbers in the greenhouse healthy, and you will no longer wonder what to do if the leaves of the crop turn yellow. I wish you rich harvests!

Excess and deficiency of nutrients

Too much fertilizer can also negatively affect the development of cucumber seedlings, as can its lack. With excessive use of natural or chemical fertilizers, yellowness appears on the leaves, and the growth of the bush itself stops.

Cucumbers should be fed in the spring (once a month) and in the summer (2 times a month). The procedure is carried out with exact adherence to the dosage.

Pests

Cucumbers require regular and abundant watering, but high humidity combined with high temperature create favorable conditions for the development of pests. It is important to react in time and take the necessary measures, otherwise the foliage will begin to turn yellow and the plant will die very soon.

Root nematode

A fairly common problem, especially in areas where the soil has not been changed for a long time. The worms lay their eggs in the ground, and the rhizomes of cucumbers become the habitat of the larvae.

The presence of a nematode can be determined by characteristic swellings, after which the roots acquire a brown tint, become thick and fragile.

What to do: Regular renewal of the top layer (at least 10 cm) of soil will help, which should preferably be done annually. The proximity of cucumbers to radishes, cabbage and garlic will help get rid of nematodes - the pest does not like them.

Whitefly

The reason why cucumber leaves turn yellow in a greenhouse may be a whitefly invasion. Small butterflies of a gray, yellow or whitish hue resemble moths in appearance. Whitefly larvae feed on plant sap, and adults carry microorganisms that are dangerous to cucumbers on their wings.

What to do: in this case, it is necessary to block the pest’s access to the greenhouse - cover the windows and doors with gauze or mesh. If insects have already penetrated inside, they must be combated by hanging sticky tape near the bushes or making special traps.

Since the whitefly loves everything that is painted yellow, a gardener can take advantage of this by smearing a cardboard trap with glue. Among the chemical preparations, Fitoverm, Aktara, Aktellik are suitable.

Slugs

The presence of the pest is indicated by characteristic holes on the fruits. In good lighting, you can also see the silvery marks left by slugs.

What to do: insects move rather slowly, so hand collection is the most effective way. It is recommended to do this in the early hours, when slugs are less active. You can create an artificial barrier around cucumber seedlings from soda ash or sand with the addition of pine needles.

Among the drugs offered by the chemical industry, Slime Eater, Thunderstorm, and Meta are suitable for fighting slugs. But they should be used with caution and not used during flowering, ovary formation and fruiting.

The rules do not apply to biological means of protection (Strela, Iskra-Bio). A couple of days after using them, you can start harvesting.

melon aphid

Small green or yellowish insects attack the ovaries, buds and leaves of cucumbers, sucking the juice from them. Plants become deformed, stop growing and die.

What to do: you need to wash the lashes with soapy water. In case of mass damage, it is recommended to burn the diseased bushes and fumigate the rest with sulfur bombs.

Thrips

These are black midges with an elongated body, pointed at the end. The presence of insects can be detected by the beige-silver stripes that they leave on the back of the leaves.

What to do: in this case, blue sticky traps will help, as well as regular spraying with an odorous infusion. To prepare it, use orange peel, onion or garlic.

Wireworm

Wireworm larvae eat cucumber seeds embedded in the soil; they do not disdain the young roots of already formed bushes.

What to do: Fertilizers containing nitrogen will help destroy the worm. But you shouldn’t get carried away with them, since an excess of this element will lead to a deterioration in the quality of the crop. It is better to plant any legume crop next to the cucumbers, which will repel parasites.

Medvedka

The pest, which lives underground, gnaws through the roots of plants, causing the foliage to begin to turn yellow and dry out.

What to do: mechanical collection will be effective, as well as pouring sunflower oil and soap solution into the detected passages.

You can also make traps: place containers with corn or millet porridge. It’s better to plant marigolds next to the cucumbers - the pungent smell of the plants will repel the pest.

Why do cucumber fruits turn yellow in a greenhouse? Causes and solutions

The harvest is approaching, but suddenly yellow fruits appear - what to do? Let's find out the reasons for possible yellowing of fruits:

• lack of copper, phosphorus and potassium;
• mosaic virus;
• over-ripening.

The process of fruit formation takes a lot of energy from the exotic. To make vegetables healthy and beautiful, you need potassium, phosphorus, and copper. The yellow border along the edge of the leaf will tell you about potassium starvation. Phosphorus deficiency is manifested by slower growth and drying out of the lower foliage. With a lack of copper, the leaves turn pale, the vines become flabby and wither.

Replenish the deficiency of microelements by adding potassium-phosphorus complex and spraying with Bordeaux mixture. Cucumber mosaic affects not only the foliage, its manifestations are also visible on the fruits - deformation, reduction in size, mosaic pattern. The surface of the green plant becomes yellow and covered with uneven green spots. Experienced gardeners destroy the bush when the disease has just appeared on the foliage.

Attention! It is difficult to confuse cucumber mosaic with other diseases, but an inexperienced gardener may make a mistake. Then he will see vegetables mutilated by the virus.

With dense plantings, harvesting is complicated; it is quite easy to miss the fruits. The vegetable is eaten green until the seeds inside have ripened. If an accidentally forgotten fruit reaches the stage of biological maturity, its surface will turn yellow or brown. Such fruits are suitable for livestock feed or for collecting seed material. Remember that the F1 series of hybrids does not inherit maternal qualities. If you bought seeds with this marking, it makes no sense to collect seed from them.

Diseases

Leaf blades may change color due to disease. Most often, cucumbers suffer from fusarium and pythiosis. These are fungal infections characterized by darkening and subsequently yellowing of foliage.

As a rule, the fungus appears after a sharp change in temperature, therefore, for the purpose of prevention, it is recommended to treat the seedlings with Fitosporin.

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What to do if cucumber foliage withers and dries out in the greenhouse

If agricultural practices are followed, wilting of cucumber tops coupled with drying is a sign of a fungal infection. No matter what fungus infects the bushes, the cucumber cannot suppress its development on its own. You will have to help the exotic using one of the folk recipes described above or treat the lashes with a fungicide - Fitosporin, Topaz, Fundazol or Bordeaux mixture.

The spores remain viable for several years, so the greenhouse must be kept clean. Spring treatment will save the gardener from many problems. Moreover, it is necessary to disinfect not only the soil, but also the structure itself.

Know! To carry out a comprehensive disinfection of a glass greenhouse, use a sulfur bomb. This method is not suitable for structures consisting of metal, since sulfur dioxide corrodes metal products.

The use of a sulfur bomb or lump sulfur is carried out by setting it on fire on a sheet of metal. Before the procedure, seal all cracks and perform the work with respiratory protection. Remember that sulfur dioxide is dangerous to the body. Leave the lit saber in the room, close the doors and windows. After 3-4 days, re-open the room and ventilate thoroughly.

Metal structures are disinfected with a bleach solution, and wooden ones with Bordeaux mixture. After disinfection, wash all surfaces thoroughly.

Planting a crop in the same place is unacceptable, because diseases are transmitted through the soil. By observing crop rotation, the risk of damage is significantly reduced. Tomatoes, beets, cabbage, and herbs are good precursors for melons.

Advice from gardeners

Experienced summer residents are ready to share tips on how to avoid yellowing of cucumber foliage when growing crops both in a greenhouse and in open ground:

1. To normalize the climate, you can place a large dark container of water at the entrance to the greenhouse. During the day it will take part of the heat for itself, and at night it will heat the air.
2. Fitoverm will help against spider mites. The drug is absolutely safe, and three days after treatment, the crop is ready for harvest.
3. If the cause of yellowness is a lack of nutrients, use sifted ash (300 g) and dry mullein (200 g). Pour the components with water (10 l) and mix thoroughly, leave for a day. Feed the bushes at the rate of 1 liter of solution per plant. Carry out the treatment once a week.

As you can see, there are quite a few reasons why the leaves of cucumbers in a greenhouse turn yellow. And how to deal with this phenomenon depends on the problem. The expert advice presented above will help.

Treatment methods for cucumbers when spots appear

Having understood what violations were made in agricultural technology, you can correct the care and correct the situation. If the foliage of diseased plants turns yellow, treatment should be started immediately using various means.

Folk ways to combat yellowing of leaves of greenhouse cucumbers

You can try to cope with the disease without resorting to the use of potent drugs. In the first stages of damage, it is possible to make do with improvised means.

What to do if cucumber leaves turn yellow in the greenhouse:

• Soda (50 g) diluted in hot water (10 l) helps with peronosporosis. It is also recommended to add a little soap to the solution. The cooled mixture is sprayed onto the cucumbers and the soil underneath them. Two treatments are required with an interval of 7 days.
• Spraying with onion infusion helps against downy mildew and bacteriosis. To prepare the composition, soak the husk in warm water, let it sit for two days, then filter the liquid and dilute it with water in a ratio of 1:5. Treatment is carried out in the evening once every 10 days.
• Fusarium disease recedes after spraying an infusion of ash on the bushes (a glass of it is diluted in 2 liters of boiling water) with the addition of soap. Also effective are solutions of whey (4 l/bucket of water) and a composition with milk and iodine (liter of milk, 150 drops of iodine, 250 g of grated laundry soap).
• Bacteriosis can be dealt with using boric alcohol and brilliant green (a teaspoon each), which are diluted in a bucket of water. The mixed composition is used for spraying. Treatment frequency: once every 3 weeks.
• Treatments with mustard and garlic solutions are effective against powdery mildew. Horsetail infusion also helps. The plant in an amount of 1 kg is infused for a day in boiling water (10 l), after which the liquid is boiled twice (brought to a boil), filtered and diluted with water in a ratio of 1:5. 3 treatments are required with a break of 5 days. You can spray (once every 14 days) cucumbers with a solution of potassium permanganate (2 g/10 l of water).

Folk remedies are the simplest and safest way to protect plants.

Chemical and bactericidal preparations

Insecticides and biological agents are likely to help cope with yellowing of leaves caused by the disease.

• Ridomil and Profit are used against peronosporosis. In the active stage of the disease, Kurzat and Oksikhom are effective.
• As soon as powdery mildew is detected, it is necessary to treat the bushes with Topaz, Pure Flower or copper sulfate. Infected foliage is torn off and burned.
• Fusarium can be controlled with the help of biological products. They are safe for both humans and the environment, but are quite effective against fungi and viruses. Fitosporin, Arbotrin, Trikhovit, Fundazim are effective in the fight against Fusarium wilt.
• Bacteriosis is treated with compounds containing copper (Kuprolux and Abiga-Peak), organophosphorus substances (Previkur Energy) and the bioantibiotic Fitolavin.

Soaking planting material in Fitosporin-M helps not only protect plants from infection, but also increase their immunity, which allows the crop to more easily survive stressful situations.

• You can cope with spider mites by spraying Fitoverm and Akarin.

How to feed plants against yellowing

Cucumbers are capricious about soil quality. If it lacks potassium, magnesium or phosphorus, the leaves growing in the lower part of the stem begin to turn yellow. A lack of nitrogen manifests itself in a change in the color of the entire green mass. Mineral fertilizers and organic matter help to compensate for nutritional deficiencies and get rid of yellow spots.

How to feed the plants:

• A urea solution (50g/bucket of water) nourishes the crop when spraying the leaf blades. It is also used for root feeding.
• Rotted compost applied under the bushes provides cucumbers with several important macroelements: nitrogen, potassium, calcium, phosphorus and iron.
• You can mix complex fertilizer yourself by taking 10 g of ammonium nitrate, potassium sulfate and superphosphate, which are diluted in a bucket of water.
• Ash helps replenish potassium deficiency.