Causes and treatment of brown and olive spots on cucumber leaves

Cucumbers

When growing cucumbers, some vegetable growers encounter brown spots on the foliage. These are often caused by the gardener themselves, due to poor care or failure to follow proper agricultural practices. Sometimes, they are the result of insect attacks or dangerous diseases. Before deciding how to treat brown spots on cucumber leaves, determine the cause. Only then can you begin restoring the plants.

Causes of brown and olive spots

Brown or olive-colored spots on cucumber tops often appear as a result of improper gardening practices or violations of agricultural practices. The main causes of spotting include:

failure to observe crop rotation rules and growing vegetables after unsuitable predecessors;
poorly chosen location for planting a garden bed;
improper soil preparation;
insufficient amount of sunlight;
exposure to drafts;
sudden changes in air temperature;
too dense planting of bushes.

Another cause is poor care of permanently planted plants. Some vegetable growers neglect irrigation guidelines and use unheated water. Failure to loosen the soil and remove weeds weakens the plants. This reduces the supply of oxygen to the root system, creating unfavorable conditions for the development of diseasesA lack of timely and regular fertilizing also causes various spots on leaves due to an imbalance of nutrients in the soil.

Spots on cucumber tops are caused by fungal, bacterial, and viral diseases. Without proper treatment, the affected areas dry out and fall off, their color changes, and holes form in the leaf blades.

Cladosporiosis of cucumber

The disease is also known as brown olive spot. In the initial stages of the disease, angular brown spots appear along the edges of the leaf blades. Gradually, their color changes, becoming olive. A yellowish border develops along the edges. Weeping brown ulcers form throughout the plant. A fluffy mycelium develops on the underside of the leaf blades in the affected areas. Conidiospores form at the tips of these myceliums. Initially, there are few of them, but as the mycelium develops, they multiply and increase in number.

After a short time, a brown coating forms on both sides of the leaf blade. Holes from fallen dead plant tissue appear in the damaged areas. The leaves become deformed due to the disease.

Important!

The incubation period for Cladosporiosis is 4 to 5 days. The disease develops best when daytime temperatures reach 30°C and drop to 12°C at night. Humidity should be maintained at 95%.

Anthracnose

This fungal disease, also known as copperhead, affects cucumbers and other vegetables. High humidity and intense heat facilitate the rapid spread of the infection. Light, brown spots appear on the leaf blades. Lower leaves are initially affected. The infection then spreads to the entire plant. As the disease progresses, the spots increase in size and merge into large circles. The disease disrupts photosynthesis and causes stems to become brittle. In dry weather, the affected areas dry out. If rain continues, rot sets in.

Ascochytosis

The disease affects all parts of the cucumber plant. Foliage is most often affected during the period of fruit formation and ripening. Brown pycnidia appear along the edges of the leaf blades. They later take on a yellowish tint. They are arranged irregularly. As the disease progresses, the affected areas dry out and fall out. Holes up to 4 cm in diameter form on the leaves. In severe cases, the foliage is completely covered with holes. This disrupts photosynthesis, and the leaves die.

Peronosporosis

Downy mildew is a disease caused by pathogenic microorganisms that attack cucumber foliage. The disease is triggered by sudden changes in daytime and nighttime temperatures. Cold water irrigation and dew precipitation can also cause downy mildew. Downy mildew develops rapidly, and within a few days, it can destroy a large portion of the crop.

A grayish coating forms on the underside of affected leaves. Yellow-green spots appear on the upper surface of these areas. Black spores mature within the plant tissue. As the disease progresses, the spots increase in size and change color. The leaf blade becomes deformed and dies. Downy mildew causes photosynthesis disruption and nutrient deficiencies. After the dead leaves fall, the infection penetrates the soil and persists there until favorable conditions arise.

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Angular spotting

In the initial stages of the disease, dark or brownish, irregularly shaped spots appear on the leaves. In high humidity, mucus droplets form on the underside of the affected leaf blades. The surface of the leaves becomes covered with an oily coating. In extremely dry conditions, the affected areas dry out and become covered with a gray crust. The leaf tissue crumbles and falls out, causing numerous holes to form. As the disease progresses rapidly, only the veins remain.

Angular spot is also called bacterial blight. The disease affects cucumber plants at all stages of development. All parts of the plant are affected by angular spot.

Gray rot

This disease is caused by unsuitable climatic conditions for growing vegetables. It occurs due to low temperatures and high humidity. Signs of damage appear on all parts of the plant. Brown, water-soaked spots form on the leaves. After a short time, they enlarge, merging into a single area. A gray coating then appears on the affected areas.

Control measures

To successfully treat brown or olive-colored spots, the cause must be identified. Only then can the treatment begin. Folk remedies or chemicals can be used to restore the plants. But first, create favorable conditions for successful vegetable growth:

when growing crops in greenhouse conditions, maintain an optimal air temperature of +25°C during the day and +18°C at night;
To maintain moderate humidity, organize regular ventilation in the greenhouse;
If the soil is excessively moist, stop watering for a while to allow the soil to dry out;
maintain a favorable microclimate in the greenhouse;
All interior surfaces in the room are disinfected.

Folk remedies

Spraying the cucumber plants with a milk-iodine solution helps treat most cucumber diseases. It's prepared by mixing 30 drops of iodine in 1 liter of milk. For better adhesion, add a few shavings of laundry soap to the solution. Spray the cucumber plants with the prepared solution every 10 days.

To prevent downy mildew, spray with garlic infusion. To prepare it, peel and chop 50 g of garlic. Pour 1 liter of water over the garlic paste and let it steep for 24 hours. After straining, bring the volume to 10 liters. Spray the plants with the infusion every 2 weeks.

A soap-ash solution protects cucumbers from many fungal infections. It is used at the first sign of disease or as a preventative measure. To prepare the infusion, mix 1 cup of wood ash and 2 liters of boiling water and let it steep for 48 hours. Then, mix the infusion with a small amount of shavings of laundry soap. Spray the solution weekly.

A milk solution prevents the development of many fungal infections on cucumbers. To prepare it, the whey is heated to 25°C and mixed with water in a 1:7 ratio. The resulting solution is sprayed on cucumber plants once every 7 days.

A decoction of onion peels cures many cucumber diseases. It is also used for preventative purposes. To prepare the decoction, mix 100 g of onion peels with 10 liters of water and boil for 30 minutes. After cooling, strain the decoction and dilute it with the same amount of clean water. Spray the bushes with the solution or water it at the roots.

Important!

Folk remedies for fungal diseases of cucumbers are effective only in the initial stages of infection. They are ineffective in severe infestations.

Chemicals

To treat ascochyta blight, cucumber plants are sprayed with a 1% Bordeaux mixture. A solution of 10 liters of water, 5 g of copper sulfate, and 10 g of urea also produces good results. This procedure is repeated three times, 10 days apart. To eliminate signs of infection on the stems, the affected areas are coated with a mixture of equal parts copper sulfate and crushed chalk.

To protect against angular leaf spot or bacterial blight, treating seed before planting is helpful. Treatment is carried out with TMTD. The application rate is 4 to 8 g per 1 kg of seed. An alternative is to treat the planting material with Fitolavin 300. This same product is used to treat bushes if plants are already infected. Spraying is carried out with a 0.2% solution.

At the first signs of Cladosporiosis, cucumber plantings are sprayed with a 1% solution of Bordeaux mixture. Throughout the season, to prevent the disease, the bushes are treated with a 0.4% solution of copper oxychloride. Spraying is carried out four times at 12-day intervals.

At the initial stage of development downy mildew Spraying plants with a 1% Bordeaux mixture effectively eliminates symptoms of the disease. Alternatively, use any fungicidal preparations containing copper. A solution of 10 liters of water and 1 g of urea is also used for treatment.

At the first signs of gray mold, affected plant parts are immediately removed and destroyed. The remaining parts of the bush are treated with fungicidal agents. Rovral paste or Bayleton are effective in eliminating signs of the disease. They contain ingredients that destroy the pathogen upon contact.

Preventative measures are effective in combating anthracnose. To prevent the disease, cucumber plants are sprayed weekly with a 1% solution of Bordeaux mixture. If the plants are already infected, the affected areas are treated with a 0.5% solution of copper sulfate. They are then dusted with crushed charcoal or lime.

Prevention

Any disease affecting cucumber crops significantly reduces yield and weakens the plants. Treating them takes a lot of time and effort. Therefore, it's better to prevent a disease than to deal with the consequences of an infection. To prevent infections, cucumber plants are periodically treated with biological products. These are harmless, don't accumulate in the soil, and don't destroy beneficial microorganisms.