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

2024 Author: James Gerald | [email protected]. Last modified: 2023-12-17 14:00

The climatic conditions of some regions do not allow growing a full-fledged crop in the open field, therefore, gardeners use greenhouses, covered films or polycarbonate greenhouses for these purposes. Inside, a cucumber-friendly atmosphere is created. But sometimes it happens that the leaves turn yellow. Find out why this is happening and how to deal with it.

Causes of yellowing leaves

Before proceeding to solve the problem, it is necessary to establish the cause of this phenomenon and revise the rules for caring for plants. Indeed, with the development of any disease, it is necessary to act promptly so as not to lose the entire crop.

The main factors provoking the appearance of yellowness on the leaves:

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

Lack of lighting

In this case, yellow spots appear at the edges of the leaves. Gradually, the leaf plate begins to dry out, which can negatively affect the further development and fruiting of the bushes.

Planting density

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

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

Exposure to high temperatures

Under the influence of sunlight, the upper leaves of the cucumbers change color and turn yellow. To prevent burns, you should limit the access of the sun to the greenhouse.

Low air temperature

Cucumbers are thermophilic plants and are very susceptible to cold snaps. 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 with the help of a special material (spunbond, agrotex), which needs to cover the plants at night.

Damage to the root system

Mechanical damage to the roots can also lead to yellowing of the foliage and the death of the entire bush. This happens most often when the rules for transplanting and loosening the soil are violated. It is recommended to control weeds by mulching, not allowing them to be mechanically removed from the ground.

Excess moisture

Excessive irrigation leads to decay of the roots and death of the bushes, so you need to water abundantly, but carefully. The water should be at room temperature. Only in this case will the plants respond with abundant flowering and an excellent harvest.

Lack of moisture

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

Too cold water is also not suitable for irrigation, since it provokes cooling of the soil, which makes the leaf plates turn yellow, and the whips themselves dry out. Watering the cucumbers should be at the root, since water ingress on the foliage can also lead to a change in its color. The procedure is carried out in the absence of sunlight - late in the evening or early in the morning.

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Excess and deficiency of nutrients

Too much fertilizer can also negatively affect the development of cucumber seedlings, as well as their lack. With excessive use of natural or chemical dressings, 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 / month). The procedure is carried out with exact adherence to the dosage.

Aging foliage

This is another reason why cucumber leaves turn yellow in the greenhouse. It is recommended to combat this by simply removing the damaged plates, which will allow the remaining leaves to receive more nutrients from the soil.

Insufficient pollination

To fix the problem, it is enough just to periodically open access for insects to the greenhouse.

Pests

Cucumbers require regular and abundant watering, but high humidity combined with high temperatures 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.

Gall nematode

Quite a 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.

It is possible to determine the presence of a nematode by the characteristic swellings, after the appearance of 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 the soil will help, which should preferably be carried out annually. The neighborhood of cucumbers with radishes, cabbage and garlic will help to get rid of nematodes - the pest does not like them.

Whitefly

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

What to do: in this case, it is necessary to close the pest's access to the greenhouse - to hang the vents and doors with gauze or mesh. If the insects have already penetrated inside, it is necessary to fight them by hanging adhesive tape near the bushes or make special traps.

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

Slugs

The presence of a pest is indicated by characteristic holes in the fruit. In good light, you can also see the silvery footprints left by the slugs.

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

Of the drugs offered by the chemical industry, Slug-Eater, Thunderstorm, 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 already start harvesting.

Melon aphid

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

What to do: It is necessary to wash the lashes with soapy water. In case of mass defeat, 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.

In this case, sticky traps of a blue tint will help, as well as regular spraying with an odorous infusion. For its preparation, use orange peel, onion or garlic.

Wireworm

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

What to do: fertilizers containing nitrogen will help to destroy the worm. But you should not 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 legumes next to the cucumbers, which will scare off parasites.

Medvedka

The pest that lives underground gnaws at the roots of plants, causing the foliage to turn yellow and dry.

Mechanical collection will be effective, as well as pouring sunflower oil and soap solution into the detected passages.

You can also make traps: arrange containers with corn or millet porridge. And it is better to plant marigolds next to cucumbers - the pungent smell of plants will scare away the pest.

Diseases

Leaf blades can change color due to disease. Most often, cucumbers get sick with fusarium and pityosis. These are fungal infections characterized by darkening, and subsequently yellowing of the 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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Gardener Tips

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

1. To normalize the climate at the entrance to the greenhouse, you can put a large dark container with water. During the day, it will take some of the heat for itself, and at night it will heat the air.
2. Fitoverm will help with spider mites. The drug is absolutely safe, and three days after processing, the crop is ready for harvest.
3. If the reason for the appearance of yellowness is a lack of nutrients, sifted ash (300 g) and dry mullein (200 g) are used. Pour the components with water (10 l) and mix thoroughly, leave for 24 hours. Feed the bushes at the rate of 1 liter of solution per plant. Carry out processing once a week.

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 advice of experts presented above will help in this.

Summarize

1. Cucumber foliage turns yellow due to improper irrigation organization, due to temperature extremes, infection with any disease, or as a result of a pest attack.
2. Timely treatment and adherence to the rules for caring for plants will help to cope with the problem.
3. For treating bushes, you can use both chemical and natural remedies. In this case, it is necessary to adhere to the indicated dosage, otherwise the plant will die.