Rusty spots on cucumber leaves: causes

Rusty spots on cucumbers can be caused by improper care, pest infestations, temperature fluctuations, or one of several common diseases. Often, the problem arises from a lack of minerals necessary for growth and fruit formation. You can only combat symptoms by correctly identifying why they appeared.

Causes of rust on leaves

The main cause of brown spots is fungi. They spread rapidly, persist in the soil, and quickly infect plants. Spores are harmful not only to leaves but also to the future harvest. Prevention is better than cure. While pathogens can vary, they all thrive in moist environments. Therefore, proper watering is essential for healthy cucumber growth.

Red spots may be a sign of:

• infestation with copperhead, black rot;
• the appearance of angular spotting;
• the appearance of pests: aphids, spider mites;
• mosaic virus;
• deficiency of nutritional minerals;
• downy mildew damage.

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The appearance of brown spots can be preceded by a sudden climate change, cold snaps, or prolonged heavy rains. Diseases often occur when cucumbers are planted in greenhouses: greenhouses have a more closed environment than open ground, so the harmful microclimate can have a significant impact on the crops.

Pests

Brown spots appear due to melon aphids or spider mites. These pests occupy the leaves, sucking out all the nutrients from the plant and accelerating the wilting process. Pests are just as dangerous as diseases, so don't underestimate them. In just a week, they can significantly reduce your garden yield. As a preventative measure, spray your crops once a week with a solution. This can be an insecticide or a folk remedy. Chemicals are only suitable for the early stages of growth, while folk remedies can be used at any stage.

Spider mites suck all the plant's juices, settling on the undersides of leaves. This results in rust, and the leaves and stems themselves develop a light webbing, which gives the pest its name. There are several methods for controlling the mite.

1. Pour clean water over the potato tops at a ratio of 1:10. A bucket of water and a kilogram of leaves will suffice. Let the infusion sit for 5-6 hours and then spray a thick layer over all the cucumbers.
2. Prepare a marigold infusion. Pour 3 kilograms of dried flowers into twice as much water and let sit, covered, for 2 weeks. Filter the infusion and combine it with a small amount of soap; this will help the infusion adhere to the leaves. Spray the cucumbers with a spray bottle.
3. Cover the green parts of the tomatoes with water in a 1:2 ratio. Bring to a boil and simmer for half an hour. Then pour in a small amount of soap, dilute with the same amount of clean water, and water the plants. It's best to do this in the evening to avoid direct sunlight burning the leaves.

Melon aphids are no less damaging to plants. In addition to the appearance of brownish spots, they can be noticed by curling leaves. If the pest isn't stopped in time, the leaves will begin to fall off and the plant will wilt. You can also combat them with folk remedies.

1. Baking soda and soap solution. Add 25 grams of baking soda and 40 grams of grated laundry soap to a liter of warm liquid. Mix the mixture and apply to the plants using a spray bottle.
2. Pepper mixture. Finely chop the hot pepper and dilute with water in a ratio of 1:3. Bring to a boil for an hour. Let it steep for a couple of days. Dilute the concentrate in a ratio of 0.2:10 and spray on your plants.
3. Dandelion infusion. Pour half a kilogram of dandelion roots and the same amount of greens into a bucket of water and let steep for 3-4 hours. Water the plants.

Diseases

Rusty spots on cucumber leaves can be caused by fungi, infections, and viruses. The discoloration may begin with olive or yellow, but along with other symptoms, it's possible to recognize the disease and prevent its spread or remove the offending plant from the garden.

Cladosporiosis

This fungus is known as olive spot. It attacks the plant gradually, beginning with irregular, rusty spots. These gradually darken, resembling a scorched edge. The leaf becomes thinner and more perforated. The fungal spores spread to ripening cucumbers, appearing as brownish bruises.

Cladosporiosis thrives in cool, damp conditions. If temperatures drop to 16°C (61°F), cover the beds with a protective layer. This can be removed during the day if it's warm enough outside. Watering should be stopped for at least 7 days until the soil becomes moist. It should be kept moist but not soggy; too much moisture accelerates the fungus' development. Plants can be treated with:

• 1% solution of Bordeaux mixture;
• 0.4% solution of copper sulfate;
• 0.2% solution of the drug "Oxychom", diluted according to the instructions

To increase resistance to disease and temperature fluctuations, soak seeds in a strengthening solution and harden them. To harden, place the seeds in a damp cloth and refrigerate for 48 hours. After this, they are ready to be planted as seedlings.

Downy mildew

It begins as a yellowish rash, which eventually turns reddish or brown. The leaves gradually wilt and dry out. The spread of the disease leads to the death of the plant if not stopped promptly. Stop watering to deprive the fungus of a favorable environment. Treat affected plants with a copper sulfate solution or Ridomil or Ordan. Protect crops from frost, especially after sunset, if grown outdoors.

Copperhead

The scientific name for this disease is anthracnose, but "copperhead" accurately describes its nature. Rust appears on cucumbers immediately: the leaves are literally covered in brown spots. They resemble burns, especially as the plant begins to dry out. The disease spreads to the fruit, causing rot and ulcers. Often, the cause is poorly produced seeds from an infected plant. To prevent the disease from spreading, treat the seeds with a disinfectant solution before planting.

You can combat the disease using the same methods as in the previous ones: solutions of Bordeaux mixture and copper sulfate. Spray the solution on healthy areas, and remove damaged ones if possible. It's too late to use chemicals during the ripening stages of the fruit, as they can damage the harvest. An alternative is an onion solution. It can be prepared at home. Boil onion peels in water, and let the resulting infusion sit for 7 days. Use a liter of the infusion for each plant.

Mosaic

The appearance of spotting may indicate infection with the cucumber mosaic virus, a common pathogen. An infected plant cannot be treated: it must be removed from the garden bed and burned in a separate area. Afterward, treat the crops and soil with a disinfectant. The virus can be transmitted by weeds or plant debris in the soil. Carefully remove all debris remaining from the infected plant.

Mineral deficiency

Brown spots accompanied by drying leaves may indicate a deficiency of the mineral nutrients needed for vigorous growth. Initially, the plant requires large amounts of nitrogen: it accelerates metabolism and is responsible for the growth of the green parts. Then comes phosphorus, which helps fruit develop and provides them with vitamins. Potassium and magnesium are equally important for cucumbers.

With a potassium deficiency, the plant's appearance is little different from normal: the problem can be seen at the tips of the leaves, where they turn brown and begin to curl. With a magnesium deficiency, the reddish tint begins to spread across the entire leaf, starting from the center and along the veins. As soon as you notice a mineral deficiency, apply it along with a mineral fertilizer.

Mistakes in care

Improper care often leads to diseases, nutrient deficiencies, and infection. Cucumbers thrive in warmth and moisture, but care must be taken when handling them. Soil temperatures should be above 15°C (59°F), and air temperatures should be between 18-22°C (64-72°F). Humidity in a greenhouse, where you can control it, should be between 70-80%.

Water plants frequently, but avoid flooding the soil. If you rarely visit your garden, set up an automatic watering system or mulch the soil. If you suspect fungal disease, stop watering immediately until the soil dries out. When temperatures drop sharply, cover plants with plastic to prevent disease. Avoid leaving plant debris in the garden beds, as it may harbor dormant pathogens.

Prevention

Brown spots on cucumbers can appear at any time and ruin the harvest. To avoid this and the need for emergency control measures, it's best to act proactively and prevent problems. Follow these steps to preserve your harvest and strengthen your cucumbers' immune system.

1. Disinfect the seed material before planting the seedlings.
2. Practice crop rotation: you cannot grow the same crop in the same place all the time.
3. Ensure good soil aeration; this will allow roots to access air and improve metabolism. If the problem is only a magnesium or potassium deficiency, loosening the soil may solve the problem.
4. Water your plants only with warm water. Cold water weakens their immune system and accelerates the development of fungal diseases.
5. Clean and disinfect the soil before planting the next batch of cucumbers. Viral and fungal pathogens may remain in the soil.
6. In the greenhouse, it is essential to disinfect surfaces: fungi can survive on them.
7. Inspect your plants to spot problems early.

Preventative treatment can prevent disease, repel pests, and improve crop health. It should be done once a week. Chemical treatments can be used initially, but after flowering, only folk remedies, biological fungicides, and insecticides are recommended.

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Folk remedies:

• whey diluted with water 1:10;
• an infusion of wood ash, left to steep for two days;
• weak solution of potassium permanganate for spraying.

Chemicals:

• Bordeaux mixture;
• copper sulfate;
• Oxychom.

Spraying should be done in the evening, when the sun has almost set. This will prevent the leaves from getting sunburned, which can also cause browning. The concentration should be low; too strong a solution will burn the leaves. Temperature isn't as important when spraying, but it's best to use room-temperature solutions to protect the crops.

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Brown spots on leaves can be removed with chemicals or folk remedies. These symptoms may indicate the development of a disease, a fungal infection, improper care, or a nutrient deficiency. The problem can be cured, especially if recognized in its early stages. To do this, conduct regular visual inspections, identifying the first signs promptly. If the plant is infected with a virus, it's best to destroy it; nothing you do will help. However, other diseases are treatable.