6 Causes of Yellow Cucumber Leaves and How to Fix it

Cucumbers grown at home are preferable to those sold in stores because they taste much better. With this in mind, however, home-growing cucumbers come with their issues. For several gardeners, one concern is the uncertainty around cucumber leaves turning yellow, its causes, and treatment. In response, I have pinpointed the likely problems for your fruit’s future and ways to handle them.

Causes and Treatment of Cucumber Leaves Turning Yellow

Cucumber Leaves Turning Yellow

Here are the different causes and treatments of cucumber leaves turning yellow:

1. Soil is Nutrient Deficient

It is common knowledge for every gardener and farmer to know that rich soil nutrient content is essential for the proper growth of all fruits and plants.

I recommend performing a soil test first to know the nutrient or nutrients the soil may lack and act accordingly. Lack of nitrogen, potassium, or iron in the soil can cause cucumber leaves to turn yellow.

Treatment of Nitrogen Deficiency in The Soil

Lack of nitrogen can lead to the death of your cucumber plant, as nitrogen aids growth and foliage, ensuring healthy-looking leaves.

Add nitrogen to the soil by spreading a few 15 ml in quantity or tablespoons of well-balanced fertilizer around the plant soil. Make sure to follow the instructions on the product because not doing so could affect the plant adversely.

With time, as it begins to flower, add a tablespoon of ammonium nitrate to the soil and a little compost. Do this again after twenty-one days.

Treatment of Potassium Deficiency in The Soil

As flowering begins on the cucumber plant, more potassium is required to help it. If attention is not paid to this, the cucumber leaves begin turning yellow with time. So, fertilizer with the appropriate amount of nutrients, particularly potassium, should be applied to solve it.

Treatment of Iron Deficiency in The Soil

When the new leaves from the cucumber plant are yellow but have green veins, it indicates an iron deficiency in the soil where the cucumber is planted. To remedy this, spray the plant foliage with liquid iron or scatter granular iron around the roots.

2. Diseases That Affect Cucumber Plant

Downy Mildew on Cucumber Leaf
Downy Mildew

Several diseases, like downy mildew, cucumber mosaic virus, and fusarium wilt, are known to infect cucumber plants and can lead to the yellowing of their leaves.

Treatment of Downy Mildew in Cucumber Plants

The specie of water mold called pseudoperonospora cubensis is responsible for downy mildew on cucumber. The disease forms yellow spots on the plant’s leaves, which end up brown. To treat this, quickly apply fungicides to the plant, and uproot any other infected plants. You can also prevent it by planting cucumber varieties with strong resistance to the disease. Also, when planting, space out your cucumber plants well enough for good air circulation to dry them, as downy mildew thrives in humid or wet conditions.

Treatment of Cucumber Mosaic Virus in Cucumber Plants

This virus can spread rapidly across a cucumber and several plants around. Light mosaic patterns with yellow dots on leaves signify the virus. To treat this, remove all infected cucumber plants and others that can harbor it.

Treatment of Fusarium Wilt in Cucumber Plants

Damping-off, stunted growth and yellowing are signs of fusarium wilt on the cucumber plant. To treat it, you must remove the infected cucumber plants.

Treatment of Verticillium Wilt and Powdery Mildew in Cucumber Plants

Verticillium Wilt is a disease that leaves a brown or tan streak on the plant’s stems, causing the lower leaves to wilt, turn yellow, die, and then dry up.

Powdery mildew, which causes white and powdery spots on the leaves and stems of cucumbers, is another cause of cucumber leaves turning yellow.

Using fungicides and removing infected leaves and plants can treat verticillium wilt and powdery mildew.

3. Pest Attack

Cucumber Leaves can turn yellow when pests such as potato leafhoppers, whiteflies, spider mites, and aphids feast on their sap. In doing this, these pests can terminally end the plant’s life.

Treatment of Pest Attack

In treating it, you can spray insecticidal soap on the plant leaves. You can also make use of row covers. Additionally, encourage beneficial insects like lacewing, minute pirate bugs, and ladybugs. These all eat potato leafhoppers.

4. Inappropriate Amount of Water on Plant

Insufficient and inconsistent watering of the cucumber plants can lead to cucumber leaves turning yellow. A consistent average of two inches of water is needed weekly for the plant to grow well.

On the other hand, excess water supplied to the cucumber plants can lead to yellowing leaves, which are also signs of nutrient deficiencies or even root rot, leading to the death of the plant.

Treatment of Inappropriate Amount of Water on Plant

Hence, a proper drainage system is required for it to thrive; this is why drip irrigation is advisable and better suited for cucumber plants when correcting this issue.

5. Insufficient and Inconsistent Sunlight on Plant

Every plant needs sunlight, and Cucumbers need an average accumulated sunlight of between six to eight hours daily. When there is insufficient sunlight for the cucumber plant, it can lead to the yellowing of its leaves.

Treatment of Insufficient Sunlight on Plants

If larger leaves of plants or trees are planted around the garden blocking the sunlight from reaching the plant, you can cut the obstructing leaf branches. You can also plant your cucumbers in the garden, where they will receive adequate sunlight.

6. Excessive Heat from the Sunlight

A warm-weather crop like cucumbers thrives in temperatures between 75 to 85 degrees F. If these temperatures are exceeded, the heat stress can cause leaf drop and sunburn to the cucumber plant.

Treatment of Excessive Heat from the Sunlight

Ensuring cucumbers get adequate water supply— deeply and evenly— especially during high-temperature weather and mulching can help retain the soil wetness and keep the roots cooler.

Provide shade for your cucumbers during the hot day by placing a cloth or burlap over the plants. Remember to remove the cloth during the cooler period so the cucumbers can get enough sunlight.

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