Diseases of cucumbers

In order not to treat cucumbers for diseases, it is necessary to carry out prevention. But if the plant is already sick, then you need to properly treat it. How to find out why? Use our cheat sheet, which describes the most common diseases of cucumbers with photos.

Mučnistaâ rosa

Signs. It is easy to recognize it – small spots of white powdery coating first appear on the leaves, which gradually increase in size, merge together, and as a result, the leaves begin to turn yellow and dry out. The fruits of diseased plants grow small and not juicy (1).

Where does it come from. Spores of the powdery mildew pathogen overwinter in the soil and fall on plants with raindrops and when watering from a hose with a sprayer. The disease develops especially actively in cool, damp weather. At temperatures above 18 ° C, the pathogen stops growing, but on cool nights it attacks the leaves again.

Prevention. The first thing to remember is to observe crop rotation. Never plant cucumbers in the same place for several seasons in a row – they can be returned to their original place no earlier than after 4 years.

After the cucumbers have fruited, remove the whips from the beds as soon as possible and burn them. In addition, it is important not to overfeed cucumbers with nitrogen and water only with warm water.

In a greenhouse, it is easier to provide preventive measures – during the day you need to open doors and vents so that moist air does not stagnate there, and close them at night so that the temperature does not fall below 20 ° C.

Treatment. At the first sign of powdery mildew, treat the plants with fungicides such as Topaz, Pureflower or Topsin-M (2). If only a few leaves are affected, cut them off and burn them.

Downy Mildew

Signs. The disease begins with small light yellow spots on the leaves. Gradually, they increase in size, the leaves begin to dry out. A grayish coating appears on the reverse side of the leaves (3).

Where does it come from. The spores of this fungus also overwinter in the soil and fall on the leaves with drops. The disease progresses rapidly in cool and humid conditions. It can also be provoked by watering with cold water.

Prevention. Same as for powdery mildew.

Treatment. The first step is to stop watering and fertilizing for a while. You can treat cucumbers with HOM (copper oxychloride) or Bordeaux mixture. Ordan and Radomil also help against downy mildew (2).

Brown olive blotch

Signs. The name of this disease speaks for itself – the leaves, shoots and fruits of cucumbers are covered with brown or olive spots. On the third day, they darken and begin to increase in size.

Where does it come from. The spores of the fungus-causative agent persist for a long time in the soil and on plant debris. They are easily carried by wind, rain and watering. The disease is especially severe at the end of summer, when the nights become cold and dew often falls.

Prevention. The bulk of the spores hibernate precisely on plant debris, and therefore it is important to remove them from the garden and greenhouses in time. If you leave the tops in the winter – be in trouble next year. Of course, crop rotation must be observed, because spores also enter the soil. And it is best to water cucumbers at the root – sprinkling always leads to outbreaks of infection.

Treatment. At the first sign of illness, stop watering the cucumbers – let the soil dry out for 5 to 7 days.

For treatment, you can use Bordeaux liquid, XOM, Oxyhom and Fundazol preparations (2).

White rot

Signs. Initially, numerous white growths appear on the plant, similar to pieces of cotton wool – the disease affects all parts: leaves, shoots and fruits. Then the growths darken, become covered with mucus, the affected areas rot.

Where does it come from. The spores of the pathogen overwinter in the soil. They fall on plants with watering and raindrops. Dew, too wet soil and coolness contribute to the rapid development of the disease. The disease usually enters the plant during flowering through the stigma of the pistil (4).

Prevention. There is also a standard set of measures: it is important to observe crop rotation, remove tops from the beds in time, water according to the rules, avoiding waterlogging of the soil. And it is also important not to thicken the crops of cucumbers – in crowded places, plants get sick more often and more strongly.

Treatment. The first step is to remove the affected parts of the plant – cut off diseased leaves and fruits. If the vine is completely covered with white rot, it is pointless to treat it – the plant must be destroyed as soon as possible.

Gray mold

Signs. The disease begins with spots on the leaves – they are brown, vague, quickly merge with each other and become covered with a smoky coating. The infection also affects the fruits – they begin to rot from the side of the flower. By the way, the disease affects not only cucumbers – 200 plant species from 45 families are susceptible to it (5).

Where does it come from. Pathogenic fungi that cause this disease overwinter in the soil and on greenhouse structures. They enter the plant through wounds and pistils of flowers. The spores are spread by wind, rain, and often through gardening tools. The infection develops especially strongly in moist, cool conditions.

Prevention. It is important that cucumbers grow from each other at an optimal distance – in thickened crops, the disease develops faster. It is also important to observe crop rotation and harvest tops on time. And make it a rule to sterilize the tools with alcohol after each plant, so as not to transfer the infection to neighboring ones.

Treatment. As soon as the first signs of the disease appear, cut off all affected leaves and fruits. With a small lesion, fungicides help – Rovral and Bayleton. Severely affected plants cannot be cured – they must be pulled out and burned as soon as possible.

Root rot

Signs. This is one of the most dangerous diseases, and it does not have any external manifestations – it is impossible to notice the beginning of the development of the disease, because it affects the roots. The fact that the cucumber is sick becomes clear when the leaves suddenly begin to wither. And even watering does not solve the problem.

If you pull out such a plant, it turns out that it has practically no roots – only a rotten red stump. Affected plants usually die within a day (4).

Where does it come from. Most often, the disease is caused by pathogenic fungi, but it happens that the problem occurs due to a complex of infections – bacteria, fungi and viruses. Unlike most other pathologies, root rot develops at elevated temperatures. And improper watering – the disease can manifest itself both during drought and with excessive moisture.

Prevention. It is very important to observe the mode of watering cucumbers. And, of course, crop rotation. If the problem has occurred in previous years, treat the plants with Previcur every 2 weeks as a preventive measure (2).

Treatment. Root rot cannot be cured. But you can try to save the plants by stimulating the formation of new roots. The simplest thing is to cut off the lower leaves, lay the base of the shoot on the ground and pin it to the ground. After 7 – 10 days, the lashes will take on new roots, after which the lower part must be cut off and the rest of the shoot, along with the old root, must be dug up. And the hole needs to be covered with fresh fertile soil.

In general, make it a rule: do not buy cucumber seeds, focusing only on the picture and description on the package – manufacturers are silent about possible problems of varieties and hybrids, they print only their best qualities. Study the varieties in the State Register of Breeding Achievements (6), there is information on how severely the plants are affected by certain diseases. And buy only the most resistant varieties.

Popular questions and answers

We talked about diseases of cucumbers with agronomist-breeder Svetlana Mikhailova.

Sources of

1. Dobrozrakova T.L. Agricultural phytopathology, 2nd ed., corrected. and additional Edited by M.K. Khokhryakova // Leningrad: ed. “Spike”, 1974 – 382 p.
2. State catalog of pesticides and agrochemicals approved for use on the territory of the Federation as of July 6, 2021 // Ministry of Agriculture of the Federation, https://mcx.gov.ru/ministry/departments/departament-rastenievodstva-mekhanizatsii-khimizatsii -i-zashchity-rasteniy/industry-information/info-gosudarstvennaya-usluga-po-gosudarstvennoy-registratsii-pestitsidov-i-agrokhimikatov/
3. Akhatov A.K., Jalilov F.S. and others. Protection of vegetable crops and potatoes from diseases, M .: Moscow printing house No. 2, 2006 – 352 p.
4. Akhatov A.K., Hannibal F.B., Meshkov Yu.I. and others. Diseases and pests of vegetable crops and potatoes, M .: Association of scientific publications of KMK, 2013 – 463 p.
5. Pidoplichko N.M. Fungi-parasites of cultivated plants. Determinant Volume 2. Imperfect mushrooms // K .: “Naukova Dumka” 1977 – 300 p.
6. State Register of Breeding Achievements, https://reestr.gossortrf.ru/