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The popular cucumbers are the first choice for your own cultivation. They quickly develop a flood of green leaves, followed by yellow flowers and immediately after that small gherkins that you can literally watch growing. Satisfied specimens constantly provide new supplies. Until something is wrong. The harvest then goes downhill just like the whole plant. Unless help comes quickly and frees them from the grip of the disease.

cucumber diseases

Even the popular cucumbers are not spared from diseases. The most common diseases and their harmful symptoms are presented below.

wilt diseases

In private gardens, diseases of cucumbers, called wilt, are often encountered. The naming is due to the course of the disease, which is accompanied by the wilting of individual parts of the plant or the entire cucumber plant. The causes for the spread of these diseases are mostly to be found in unfavorable growing conditions. Below is a small overview of the wilting typical of cucumbers.

cucumber wilt

Cucumber wilt is from a fusarium fungus triggered. This fungal disease can be recognized by a damage pattern with the following characteristics:

  • first the cucumber plants wilt during the day
  • at night the leaves recover
  • they turn yellow and after a few days they dry up completely
  • a pink colored mycelium may appear at the base of the stem
  • the roots turn brown and rot

Black root rot

It is another fungal disease that particularly affects the roots of the cucumber plant. The black discoloration that occurs gives the disease its name.

  • Stem base becomes rotten
  • Roots turn black
  • then decompose over time
  • new, so-called adventitious roots form
  • the lower leaves yellow and then die

Sclerotinia stem rot

Also called sclerotia wilt for short. It primarily attacks the base of the stem, but can also spread to the cucumber fruits.

  • cotton-like fungus at the base of the stem
  • inside are 1 cm large, black fruiting bodies
  • Infested fruits also show fungal networks

stem rot

It prefers to attack cucumber plants that thrive in a greenhouse. The following symptoms are typical:

  • spreads in warm weather
  • Affected cucumber plants suddenly wither
  • die-off then follows quickly
  • the base of the stem becomes rotten and rotten
  • a greenish mycelium can also be seen there

Verticillium wilt

This wilt spreads when air and soil temperatures are low.

  • lower leaves are affected first
  • become limp and brown
  • these features often only show up on one side
  • recovery often occurs at night (as in cucumber wilt)

tip: In this fungal disease, if you cut through a stalk, gray or brown colored vessels become visible.

Measures against wilt diseases

The diseases described above, all of which bear the name wilt, cannot be combated chemically. That's why preventive measures important, mostly aimed at optimizing the growing conditions.

  • annual change of soil in the greenhouse, at least up to 25 cm deep
  • if not possible, add humus to the soil
  • annual change of cultivation area outdoors
  • Do not water cucumber plants with cold water
  • remove as many roots as possible from the soil in autumn
greenhouse cucumbers

If one of these cucumber diseases has already broken out, you should fight its spread or prevent a recurrence in the following year.

  • Pack diseased plants in garbage bags immediately on site
  • collect and destroy all leftovers
  • never put it in the compost

tip: For sclerotia wilt, be careful not to drop fruiting bodies on the garden floor.

Other fungal diseases

The various wilt diseases are not the only fungal diseases threatening our beloved cucumber plants in the home garden.


Anthracnose is also under the name focal spot disease known. It affects the entire cucumber plant.

  • Fruit buds shrink and dry up
  • Cucumber fruits get spots
  • these are watery, dark gray or brownish
  • reddish fungal spores can be seen in it
  • they spread and the cucumber dries up
  • the cucumber plant also dries up

powdery mildew

Powdery mildew is one of the most common cucumber diseases caused by fungi, which also has serious effects.

  • small spots with a white fungal covering appear first
  • these are getting bigger
  • finally the whole leaf is covered with a lawn of fungi
  • this acts like scattered flour
  • the leaves die off underneath
  • affects outdoor and greenhouse cucumbers
Powdery mildew on zucchini leaves


These fungal pathogens prefer dry and warm days. Once he's conquered a cucumber plant, there's no helping it. No corresponding fungicide is approved for cultivation in private gardens. However, there are varieties of cucumbers that are resistant to powdery mildew. In order to avoid spreading, the infested plants must of course be disposed of completely and promptly.

Wrong mildew

Even downy mildew does not stop at cucumber plants. When the weather is damp but cool at the same time, it can be found both outdoors and in the greenhouse. These signs of disease are visible on the cucumber plant:

  • at the beginning of summer spots appear on the leaves
  • they are light green or yellowish to brown
  • are limited by the leaf veins
  • the mushroom lawn has a grey-violet colour
  • can be found on the underside of the sheet
  • within a few days the foliage turns yellow
  • young fruits wither
  • eventually the whole plant dies
Downy mildew on cucumber plant


Spraying horsetail broth is helpful in fighting this cucumber disease. As a preventive measure, ensure that there is enough space between individual plants. Good ventilation is also important in the greenhouse so that diseases don't even get a chance.

gray mold

The fungal coating that often forms in cucumber diseases is gray in color here. The spores of the fungal pathogen survive for a long time in the garden soil, waiting for favorable conditions to strike again. Humid weather and dew on the cucumber leaves are ideal for them.

  • Fungus spreads to the whole plant
  • Stems, leaves and fruit bases are covered with a thick coating


Gray mold has it particularly easy on plants that are already weakened. In the greenhouse, make sure that the air can always circulate well. The humidity should not be increased unnecessarily, in particular cucumber plants should be watered close to the ground so that their leaves are not wetted with water.

viral diseases

Although viral diseases do not cause plaque, they are still life-threatening for cucumber plants, as the descriptions below show.

cucumber leaf spot virus

This virus pathogen is a greenhouse dweller.

  • young leaves form yellow-green leaf spots
  • starting from the edge of the sheet
  • a brown dot is visible in the center
  • the leaf tissue around it has blistered warps
  • no signs of disease on cucumber fruits


It is currently not possible to combat this viral disease. A diseased cucumber plant should be discarded immediately.

cucumber mosaic virus

Aphids act here as virus carriers. The action of the virus pathogens can be seen on the leaves and fruits:

  • light green spots or circles form on leaves
  • young leaves show deformations
  • few side shoots are formed
  • cucumber fruits also become blotchy
  • with temperature fluctuations, the plant wilts
  • it can also die off completely
cucumber mosaic virus


As soon as you discover aphids on your plants, you should fight them immediately so that the virus cannot be transmitted in the first place. This cannot be fought directly, the diseased cucumber plant must be disposed of immediately. Of course, this does not belong in the compost, but in the garbage can. The tool used, as well as everything that has come into contact with the diseased plant, must be disinfected to avoid further contamination.

bacterial diseases

In addition to fungal pathogens and viruses, bacteria are the third party that are targeting our cucumber plants. They usually let the cucumber fruits rot.

Bacterial soft rot

Splashes of water transfer the bacteria to the cucumber plant. These find access via damaged or eaten areas of the cucumber fruit.

  • Cucumbers get mushy from the base of the flowers
  • young cucumbers are already affected
  • diseased cucumbers smell putrid


You will not find any approved means on the market to fight this virus. All fruit showing the symptoms of the disease described above must be picked and destroyed by you as quickly as possible. Wear gloves or wash your hands afterwards to remove any germs that may have stuck.

tip: This virus also likes zucchini, carrots and onions. Whenever you suspect this virus from one of these vegetables, you should also check the others.

Angular leaf spot disease

If, at the same time, with high humidity, the temperature rises above 24 ° C, then the symptoms of this cucumber disease appear.

  • Leaves get angular spots
  • these have a yellow color that looks glassy
  • Spots become larger and brown
  • at the last stage they dry up and fall out
  • Bacterial slime can be found on the underside of leaves
  • Cucumbers get mushy, dark spots
  • there is a white dot in the middle


As a preventive measure, care should be taken to ensure that the seed is healthy, since the bacterial pathogen can be carried over from seeds that are not in perfect condition. Also browse the Internet for resistant cucumber varieties. Diseased plants must be discarded and no cucurbits grown in that patch for three years as they are all threatened by this bacterium. After that, the bacteria in the soil should be eradicated.

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