Why do cucumbers rot in a greenhouse and what to do to save your crop

It is difficult to imagine a summer without delicious, crispy cucumbers grown in your country house. Those who wish to grow early cucumbers in large quantities plant them in a greenhouse.

In protected ground conditions, a special microclimate is created with high temperatures and high air humidity. Such conditions are liked not only by cucumbers, but also by pathogens. When growing a greenhouse cucumber, the gardener is often faced with the problem of various rot of fruits and leaves. If these diseases are not treated in time, there is a risk of losing half of the crop.

Rot types

Why do cucumbers rot in a greenhouse and what to do to save your crop

Rot varies in color, location and cause. Rot happens:

  1. White. It manifests itself at any stage of the development of a cucumber. The affected parts of the plant are covered with a white, wadded, weeping bloom and dry out. If the fungus develops inside the stem, the entire infected lash becomes covered with mucus.
  2. Gray. It affects all parts of the plant, including the roots. The first signs of the disease appear in the form of light brown, slippery, vague spots on the stems and leaves. In the future, the infection spreads to the ovary. Young fruits become covered with a gray fluffy bloom, soften, become watery and flow.
  3. Brown. Brown spots appearing on young fruits. As the fruit grows, the size of the spots increases, covering the cucumbers with a marshy green bloom.
  4. Black. Rounded black spots appear on the stems, which turn brown as the infection develops and finally turn white.
  5. Root. The first "bell" that cucumbers are sick with root rot will be a strong hanging of cucumber lashes, as if the culture is very thirsty. If you shake off the soil from the root collar with your hand, you will see a brown stem thinned at the base with signs of rotting roots.
  6. Top. Young ovaries and fruits are affected. Appears in the form of single gray or brown dry spots on fruits, which, growing, turn into a continuous dense dark gray pubescence. Over time, the plaque completely covers the fruit, which becomes watery and soft. The plants themselves stop growing, the leaves begin to wither, curl and dry.

Most often, rot is caused by various kinds of fungi. But there are those that arise due to damage to plants by pests.

Leaves, ovaries, small cucumbers rot

If the stems, ovaries or even small cucumbers are covered with a gray or whitish fluffy bloom, and brown or gray spots of irregular shape have appeared on the leaves, then we are dealing with rotting processes. You should not make hasty conclusions without accurately identifying the pathogen and not understanding how and where it got on the plants.

Causes of decay of greenhouse cucumbers

So, why do cucumbers rot in the greenhouse and what to do? Many pathogens enter contaminated soil and planting material. If preventive treatments against fungal diseases and molds have not been carried out in the greenhouse for a long time, then even the walls can be a source of infection.


Most greenhouse cucumber rot is caused by fungal and bacterial pathogens. The main source is unharvested infected parts of plants of the Pumpkin family. With high humidity, the disease progresses faster.

Dampness and cold are ideal conditions for the spread and development of fungal spores. Pathogens begin to multiply, capturing more and more lashes and fruits. The trouble lies in the fact that in greenhouse conditions it is impossible to arrange the plants far from each other due to the limited area.

Root diseases:

  1. Blackleg... The disease is dangerous for seedlings. This is a complex disease, several pathogens take part in it at once: fungi, bacteria and viruses. The root collar changes color from green to dark green and becomes wet, after which the stem becomes thinner and the seedling lays down. Drafts, contaminated soil or seeds can cause the disease.Why do cucumbers rot in a greenhouse and what to do to save your crop
  2. Fusarium wilting... The disease begins with root rot. Outwardly, this manifests itself as heavily drooping leaves and whips. Withering occurs at lightning speed. Sometimes cucumbers die within 12 hours. Infection occurs when the mycelium penetrates into small cracks, wounds on whips and leaves.
  3. Root rot... It is caused by several pathogens at once: Pythium debaryanum, P. ultimum and P. aphanidermatum. The latter is dangerous not only for the Pumpkin family, but also for the Solanaceae and Legumes.

Rot of cucumber shoots and leaves:

  1. Sclerotinia or white rot. Fungal disease caused by a fungus of the genus Sclerotinia sclerotiorum. This infection is curable only in the initial stage, with the appearance of a white bloom resembling cotton wool.
  2. Gray rot. The culprit of the disease is the fungus Botrytis cinerea. Often on a cucumber affected by gray mold, a secondary infection develops - brown spot.
  3. Ascochitis. Black mycosperellus stem rot of cucumber. Only weak plants are affected. Leaves and fruits can also rot on the infected plant. The fruits turn brown and wet. The pathogen is preserved in seed material, weeds and on the walls of greenhouses.

Reference. The only rot that begins to spread from the fruit is the top rot. If the disease is not treated, the roots and the growing point of the cucumber rot. Fatty, overfed plants are prone to vertex rot.


Not only fungi and molds, but also numerous pests can cause the appearance of rot on cucumbers. Damaging the tissue of stems, leaves and fruits, insects suck juices from cucumbers. Plants become weak, and the sites of damage, like open wounds, attract fungi and bacteria.

The main greenhouse pests of cucumber that can provoke the appearance of rot:Why do cucumbers rot in a greenhouse and what to do to save your crop

  1. Melons aphid. This small pest colonizes the underside of leaves, shoots and growth point. It comes in green and black. Ants contribute to the spread of aphids.
  2. Greenhouse whitefly... Small white butterflies lead a hidden lifestyle. If you shake the plants, the insects pop up and fly. Where the whitefly has visited, whitish blotches remain.
  3. Tobacco thrips. In appearance it resembles small, oblong, white and gray bugs. It is easy to notice a small insect by the strokes and lines on the upper side of the leaf, which it leaves, sucking the juices from the plant.

Unfavorable environmental conditions

In the greenhouse, climatic conditions are created artificially. What they will be - ideal or unfavorable for the development of culture, depends on the gardener.

The spread and development of rot is facilitated by the following conditions:

  • air temperature below + 18 ° C;
  • high humidity in the absence of ventilation;
  • insufficient illumination;
  • high acidity of greenhouse soil.

Agrotechnical errors

A gross violation of measures for the care of cucumbers can become a predisposing factor for the occurrence of rot. With poor care, plants grow weakened and lag behind in development. It is easiest for pathogens to “overcome” such a culture.

We list the main mistakes in care that can contribute to the formation of rot:Why do cucumbers rot in a greenhouse and what to do to save your crop

  • untreated soil;
  • watering with cold water;
  • overdrying or over-watering cucumbers;
  • unremoved parts of diseased plants;
  • dirty glass and walls;
  • excessive application of nitrogen fertilizers or manure;
  • lack of nutrition;
  • lack of preventive treatments;
  • non-compliance with crop rotation;
  • thickened planting of bushes;
  • very deep landing.

What to do, how to save the harvest

As soon as putrefactive processes on cucumbers are found, it is necessary:

  1. Reduce watering and irrigation activities.
  2. Adjust the air temperature. If it's cold, then increase to 22 ° C. If it's hot, provide ventilation, whitewash the roof or shade with non-woven fabric.
  3. Use complex chemicals to combat. There may not be enough time to find the exact cause. Most rot spreads over several days, sometimes hours.

Important! Do not neglect the use of chemicals! Sometimes the rejection of "chemistry" has a deplorable effect on plantings. People's measures of struggle are powerless in many situations.

How to treat cucumbers from rot

The market offers a wide range of chemical fungicides of systemic, complex action on several types of fungi at once.

A comprehensive action plan to fix the problem:

  1. Any rot is treated with a complex fungicide (Topaz; Oxyhom). The preparations are dissolved in 10 liters of water.
  2. White rot every other day is smeared with a mixture of "Sumileks" and "Rovral", preparing a water chatter from them.
  3. Carry out a thorough disinfection of the greenhouse soil, glass and structures with the "HOM" preparation.

Attention! 3-4 days after processing, feed the cucumbers with phosphorus-potassium dressing. Phosphorus and potassium will help damaged tissues regain strength and strengthen cucumber's resistance to infection.

Preventive measures to prevent the problem

Why do cucumbers rot in a greenhouse and what to do to save your crop

Preventive methods of dealing with rot are no less effective. It is much easier to prevent a disease than to fight it... Prevention measures consist of the use of special biological, chemical protective measures and agrotechnical measures on healthy plants:

  • observance of crop rotation: do not plant cucumbers after any melons, tomatoes and peppers, as they have similar diseases;
  • selection of varieties and hybrids resistant to rot and associated diseases;
  • watering with warm water in the morning;
  • immediate removal of affected plants;
  • replacement of greenhouse soil every three years;
  • soil treatment in a greenhouse with a strong solution of copper sulfate;
  • annual introduction of the biological product "Trichodermin" into the soil;
  • annual spring pre-sowing treatment of greenhouse walls with "HOM" preparation;
  • dressing seeds with the preparation "Tiram" or purchasing ready-made dressing seeds;
  • one-time spraying of cucumber plantings with Planriz or 0.1% solution of "Euparena-multi" in the phase of three true leaves.

Tips from experienced gardeners

Why do cucumbers rot in a greenhouse and what to do to save your crop

Gardeners, long ago growing cucumber, know about the problem of rot firsthand. Their many years of experience will help you successfully grow cucumbers in a greenhouse and harvest a rich harvest:

  1. Provide regular greenhouse ventilation.
  2. Grow cucumbers on a trellis. Tied lashes will be easier to scan for fungus infestation and plant maintenance.
  3. Pinch the cucumber stems over 5-6 leaves, leaving the side ones for further growth. Properly formed lashes will produce bountiful crops and be strong and healthy.
  4. Be sure to carry out insect treatments and do not damage the plants when leaving.
  5. Do not pour cucumbers, and after glaze loosen the soil.


Early detection of any rot is essential for a successful therapy. However, prevention is always more effective than cure. But if the disease is already active, do not neglect chemical preparations - literally every hour is expensive. Using tips and tricks for treatment, you can save plants and reap the desired harvest.

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