Cucumbers from your own garden or greenhouse are a pleasant refreshment in summer. However, the joy is clouded when the plants, be it in the field or in the greenhouse, get sick. Therefore, you should check them regularly for cucumber diseases, because this is the hope that the diseases will not spread. 
The cucumber mosaic virus is transmitted by aphids. However, transmission can also take place through cutting tools if these have not been disinfected before use.
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If the virus has attacked the plant, compression, leaf deformation and phenomena that are reminiscent of a mosaic occur. If the temperatures are above 24 degrees Celsius, the (young) leaves turn yellow or light green like a mosaic. At temperatures below 20 degrees, the infected plant begins to wither. Warts and spots can appear on the cucumbers themselves.
Countermeasures
To protect the plants from the cucumber mosaic virus, you should make sure that no aphids nest. If an infestation has set in, the aphids must be removed immediately.
Tip: There are now many types of cucumber that are extremely robust against the cucumber mosaic virus. It is best to choose one of these varieties when buying.
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A treatment for the disease is not yet known. If you notice any abnormalities, the diseased plant must be isolated immediately and cut parts of the plant must be burned immediately. Preventive measures are:
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light- to yellow-green spots with a brown, necrotic point in the middle on the leaves
No treatments for the disease are known to date. Therefore, you should immediately dispose of the diseased plant.
Since there is currently no treatment against the cucumber diseases, the infected plants must be removed and destroyed immediately. To prevent the virus from spreading further, clean all containers, devices and hands thoroughly.
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You can recognize signs of these cucumber diseases by the following symptoms on the leaves:
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Pseudomonas lachrymans attacks leaves, stems and later also the cucumbers. Signs and symptoms of the disease are:
Only preventive measures can help against angular leaf spot disease. This includes that only disease-free seeds are used. In addition, after infestation, no more cucurbits should be planted in the appropriate place for two to three years. The soil should then be free of the bacteria again. In greenhouses, a high level of humidity (80 to 90 percent) helps against the bacteria.
Tip: There are now cucumber varieties that are resistant to the bacterium.
Powdery mildew is caused by fungi from the Erysiphaceae family. In the field, the cucumbers are mainly attacked by Erysiphe cichiracearum, in the greenhouse it is often Spaerotheca fulignea. Mildew fungi develop particularly well in sunny and dry weather. The leaves of the cucumbers are their habitat.
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At the beginning of the infection, white, flour-like spots form on the leaves. In the course of the disease, the whole leaf is covered with a light gray film, which causes the leaf to die off prematurely.
Countermeasures
The only thing that helps against powdery mildew is removing the plant so that the fungus cannot spread any further. The only way to prevent the fungus is to buy powdery mildew-resistant varieties.
Downy cucumber powdery mildew mainly affects pickled cucumbers and cucumbers in the open air and in the greenhouse.
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As with powdery mildew, there is no antidote against the wrong one. However, there are cucumber varieties that are less susceptible to downy mildew. In the greenhouse, dry cultivation can help against the fungus. You should also always ventilate the greenhouse well, even in cooler summer weather.
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Affected parts of the plant are leaves, stems, fruits and, in rare cases, the roots. Symptoms on the leaves are:
Countermeasures
As soon as you discover signs of the disease, you should remove the affected plants. A reduced humidity helps against the flight of spores. Fungal growth is slowed down by a rapid rise in temperature in the morning.
Botrytis cinerea attacks leaves, stems and fruit bases.
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All infected parts of the plant are covered with a thick, greyish layer of spores.
Countermeasures
Since the fungal spores persist in the soil, you should only water the plants close to the ground and avoid splashing water. Good air circulation in the greenhouse prevents gray mold infestation.
Fusarium oxysporum is a soil fungus that enters the plants from the substrate and blocks their pathways in the stems.
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Since the plant can no longer be supplied due to the blocked ducts, it wilts and dies as a result. You can recognize the mushroom itself by the pink fluff at the base of the stem.
This fungal infection mainly occurs in greenhouses.
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A slightly white to whitish-green fungal network can be seen at the base of the stem. If the plant is infected, it wilts almost suddenly and dies after a short time. Other signs are rot and rot on the stem base.
You can recognize this fungal disease by a white, cotton-wool-like fungal network at the base of the stem. Black fruiting bodies with a diameter of up to one centimeter develop in this area. If the fungus spreads to the cucumber fruits, then they are also covered by the fungal network.
Countermeasures
In the case of a wilt disease, the infected plant must be removed and destroyed immediately. In addition, the soil should be replaced to a depth of 25 to 30 centimeters. If this is not possible, all roots should be removed from the earth if possible.
In addition to diseases caused by viruses, fungi or bacteria, various pests can also nestle in the cucumber plants. This includes:
Viral diseases
Viral diseases of cucumber plants are now a major problem. There are currently more than 25 known viruses that cause diseases in the cucurbit family (Cucurbitaceae). Effective treatment of the plants is not possible with most viruses, so you should remove and dispose of diseased cucumber plants immediately.Cucumber moasic virus
The cucumber mosaic virus is transmitted by aphids. However, transmission can also take place through cutting tools if these have not been disinfected before use.Damage image
If the virus has attacked the plant, compression, leaf deformation and phenomena that are reminiscent of a mosaic occur. If the temperatures are above 24 degrees Celsius, the (young) leaves turn yellow or light green like a mosaic. At temperatures below 20 degrees, the infected plant begins to wither. Warts and spots can appear on the cucumbers themselves.
Countermeasures
To protect the plants from the cucumber mosaic virus, you should make sure that no aphids nest. If an infestation has set in, the aphids must be removed immediately.
Tip: There are now many types of cucumber that are extremely robust against the cucumber mosaic virus. It is best to choose one of these varieties when buying.
Cucumber green mottle mosaic virus
The greenhouse mosaic virus is transmitted to greenhouse cucumbers via the plant sap. This can be done through the soil, the seeds or non-disinfected cutting tools. Since the virus can penetrate the plant through all open wounds, chewing insects are also among the causes of the disease, even if it is not transmitted through them.Damage image
- This disease occurs in greenhouse crops. Symptoms are:
- light to dark green piebalds on the leaves
- lumpy, dark green sections on the leaf blade
- Cucumber fruits: discoloration and necrosis inside
A treatment for the disease is not yet known. If you notice any abnormalities, the diseased plant must be isolated immediately and cut parts of the plant must be burned immediately. Preventive measures are:
- only virus-free seeds or Use substrate
- only use disinfected cutting tools
- fight chewing insects with organic means
Cucumber leaf spot virus
The cucumber leaf spot virus threatens greenhouse crops.Damage image
light- to yellow-green spots with a brown, necrotic point in the middle on the leaves
- initially only on young leaves
- Blisters on the surrounding green leaf tissue
- There are no symptoms on the cucumber fruits.
No treatments for the disease are known to date. Therefore, you should immediately dispose of the diseased plant.
More viral diseases
Other viruses that cause cucumber diseases include:- Cucumber Yellowing Virus(bed pseudo yellow virus)
- Cucumber Necrosis Virus(tobacco necrosis virus)
- Arbaism Mosaic Virus(arabis mosaic virus)
- Melon Necrosis Virus(melon necrotic spot virus)
Since there is currently no treatment against the cucumber diseases, the infected plants must be removed and destroyed immediately. To prevent the virus from spreading further, clean all containers, devices and hands thoroughly.Damage image
You can recognize signs of these cucumber diseases by the following symptoms on the leaves:
- mosaic-like discoloration
- Yellowing
- Twisting
bacteria
Various bacteria can also make a cucumber plant sick.
Angular leaf spot disease (Pseudomonas syringae pv. lachrymans)
The angular leaf spot disease occurs mainly in outdoor cucumbers, but can also occur in greenhouse cucumbers. The cause is the bacterium Pseudomonas lachrymans, which overwinters on plant debris, in the seeds and in the soil. As a rule, it is transferred from the ground to the cucumbers by splashing water (rain or irrigation water). If an infestation occurs, the diseased plants must be disposed of immediately.Damage image
Pseudomonas lachrymans attacks leaves, stems and later also the cucumbers. Signs and symptoms of the disease are:
- straw yellow to light brown angular spots on the leaves
- Leaves gradually dry out
- Leaves split open
- Tissue parts tear off
- Formation of irregularly shaped holes in the leaves
- small, circular spots on the cucumbers
- diseased areas open and turn white
Only preventive measures can help against angular leaf spot disease. This includes that only disease-free seeds are used. In addition, after infestation, no more cucurbits should be planted in the appropriate place for two to three years. The soil should then be free of the bacteria again. In greenhouses, a high level of humidity (80 to 90 percent) helps against the bacteria.
Tip: There are now cucumber varieties that are resistant to the bacterium.
Fungal diseases
Fungal infections in cucumbers are just as persistent as cucumber diseases caused by viruses or bacteria. Successful control is only possible in the rarest of cases.Powdery mildew (Spaerotheca fuliginea and Erysphia cichoracearum)
Powdery mildew is caused by fungi from the Erysiphaceae family. In the field, the cucumbers are mainly attacked by Erysiphe cichiracearum, in the greenhouse it is often Spaerotheca fulignea. Mildew fungi develop particularly well in sunny and dry weather. The leaves of the cucumbers are their habitat.Damage image
At the beginning of the infection, white, flour-like spots form on the leaves. In the course of the disease, the whole leaf is covered with a light gray film, which causes the leaf to die off prematurely.
Countermeasures
The only thing that helps against powdery mildew is removing the plant so that the fungus cannot spread any further. The only way to prevent the fungus is to buy powdery mildew-resistant varieties.
Downy mildew (Pseudoperonospora cubensis)
Downy cucumber powdery mildew mainly affects pickled cucumbers and cucumbers in the open air and in the greenhouse.Damage image
- initially light green to yellow-brown spots with angular shape on the upper side of the leaf
- gray-violet coating on the underside of the leaf
- in the course of the disease: leaves turn yellow, then brown and die
As with powdery mildew, there is no antidote against the wrong one. However, there are cucumber varieties that are less susceptible to downy mildew. In the greenhouse, dry cultivation can help against the fungus. You should also always ventilate the greenhouse well, even in cooler summer weather.
Gum stem disease (Didymella bryoniae)
The fungus Didymella bryoniae is the cause of the rubber stem disease. The infection occurs mainly in greenhouse cultivation with cucumbers. The disease is transmitted through spores that stick to seeds, clothing, cutting tools and parts of plants.Damage image
Affected parts of the plant are leaves, stems, fruits and, in rare cases, the roots. Symptoms on the leaves are:
- initially brown to light beige spots on the leaf margins
- spread towards the middle of the leaf
- Necrosis
- dull and darker green tissue between diseased and healthy areas
- small, black spots on the spots (spore bodies)
- appear gray from a distance (spore bodies)
- get a rubbery consistency in the course of the disease
- yellow drops on the stems
Countermeasures
As soon as you discover signs of the disease, you should remove the affected plants. A reduced humidity helps against the flight of spores. Fungal growth is slowed down by a rapid rise in temperature in the morning.
Gray mold (botrytis cinerea)
Botrytis cinerea attacks leaves, stems and fruit bases.Damage image
All infected parts of the plant are covered with a thick, greyish layer of spores.
Countermeasures
Since the fungal spores persist in the soil, you should only water the plants close to the ground and avoid splashing water. Good air circulation in the greenhouse prevents gray mold infestation.
Wilted diseases
Various wilting diseases are also dangerous for green plants.Fusarium wilt or cucumber wilt (Fusarium oxysporum)
Fusarium oxysporum is a soil fungus that enters the plants from the substrate and blocks their pathways in the stems.Damage image
Since the plant can no longer be supplied due to the blocked ducts, it wilts and dies as a result. You can recognize the mushroom itself by the pink fluff at the base of the stem.
Stem rot (Fusarium solani)
This fungal infection mainly occurs in greenhouses.Damage image
A slightly white to whitish-green fungal network can be seen at the base of the stem. If the plant is infected, it wilts almost suddenly and dies after a short time. Other signs are rot and rot on the stem base.
Black root rot (Phomopsis sclerotioides)
In black root rot, the lower leaves of the cucumber plants turn yellow and die off as the disease progresses. Corpses can be seen at the base of the stem. The roots turn black and rot.Sclerotinia wilt or Sclerotinia stem rot (Sclerotinia sclerotiorum)
You can recognize this fungal disease by a white, cotton-wool-like fungal network at the base of the stem. Black fruiting bodies with a diameter of up to one centimeter develop in this area. If the fungus spreads to the cucumber fruits, then they are also covered by the fungal network. Verticillium wilt (Verticillium albo-atrum and Verticillum dahliae)
This wilt disease is particularly common when the soil and air temperatures are low. The first signs are sagging leaves in the lower part of the plants. As the disease progresses, they turn brown. Inside the stem there is a gray or brown discoloration of the ducts.Countermeasures
In the case of a wilt disease, the infected plant must be removed and destroyed immediately. In addition, the soil should be replaced to a depth of 25 to 30 centimeters. If this is not possible, all roots should be removed from the earth if possible.
Pests
In addition to diseases caused by viruses, fungi or bacteria, various pests can also nestle in the cucumber plants. This includes:- Cucumber aphids
- Leaf miner
- Spider mites
- Thrips
- Whitefly
- Bed bugs
