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White Spots on Cucumber Leaves [Resolved]

Cucumber is an edible vegetable that can incur white spots on its leaves due to certain anomalies.

Generally, to treat white spots on Cucumber leaves, water the plant properly, treat Powdery mildew with fungicides, repel pests, and provide ample sunlight and good air circulation.

Read on to find out what causes white spots on cucumber leaves and how to treat them.

Is It Normal to Witness White Spots on Cucumber Leaves?

The straight answer is: No. It is not typical for any plant with green leaves to have white spots all over them.

Generally, if you witness white spots on the Cucumber leaves, it may signify powdery mildew, pest infestation, transplant shock, lack of sunlight, and overwatering.

If you do not do something about the white powdery spots on the leaves, they will eventually spread across the whole plant.

The spot’s spreading mechanism will be different depending on the nature of the spot. Fungal diseases spread due to wind and watering.

The powdery mildew can eventually kill the plant if not treated in time.

How to Treat White Spots on Cucumber Leaves?

White spots on Cucumber leaves hinder the plant’s normal growth and yield and eventually kill it.

Let us look at the signs and symptoms of the conditions or diseases that can cause white spots on Cucumber leaves.

ConditionsSigns and Symptoms
Powdery Mildew (mainly caused by Podosphaera xanthii)1. White powdery-spots on the leaves
2. Leaves will curl and have blisters
Pests (Mealybugs, Scales, Aphids)1. Stunted, yellow leaves, slow growth
2. Irregular brown spots on leaves
3. Curled, out of shape leaves
Transplant Shock1. Different brown or black spots on leaves
2. Leaves start drooping
Lack of Sunlight1. Leaves turn yellow, no fruit and flower production
Overwatering1. Damaged roots, yellow leaves, limpy and stunted growth of plant

Now, let us look at the treatment of chalky white spots on your plant.

1. Provide Adequate Watering 

Overwatering significantly contributes to white spots on cucumber leaves, so it’s crucial to water them appropriately.

Generally, a Cucumber plant requires at least one inch of water weekly for healthy growth. Inadequate watering can result in bitter-tasting fruit.

You should not also overwater your Cucumber. Though it may not pose as much threat as underwatering, it still is pretty dangerous.

Due to too much water, this plant will act as a host for fungal diseases like Powdery Mildew, and its roots will also be blocked, which results in white spots on the leaves.

Also, overwatering drives away the required nutrients and make the plant swell. This ends up in the leaves turning dull and white.

If your plant is in direct sunlight, you may need to water it with 0.9 cups every seven days; otherwise, 0.8 cups every nine days will suffice.

Furthermore, water your Cucumber plants in the morning to allow the leaves to dry before nightfall. It will prevent the conditions necessary for the growth of powdery mildew.

It is ideal to water cucumbers 2–3 times in one week before they produce flowers.

In addition, the best method to water Cucumber plants is with a soaker hose or drip irrigation system, which will help to keep the leaves dry.

Moreover, use tepid, distilled, or rainwater free of chemicals while watering.

2. Treat Powdery Mildew

The plants’ fuzzy white powdery spots and dots could indicate different problems, but the most common one is Powdery mildew.

Powdery mildew is an infection caused by a fungus that appears as white fuzzy substances on the bottom and top of the leaves and can spread to other parts quickly.
Powdery Mildew in Cucumber leaves
Powdery mildew is a fungal disease that can attack your Cucumber if you do not fulfill its care requirements.

The fungus Podosphaera xanthii causes powdery mildew on Cucumber leaves.

This fungal infection usually spreads by gushing wind or water. The wind blows the fungal spores to other leaves and plants, and splashing water does the same.

The leading causes of Powdery mildew are:

  • Favorable warm conditions for the fungus; temperatures that range from 65 to 80°F.
  • When the plant stays out of the sun in shady conditions for a long time, it becomes susceptible to attack.
  • Too much humidity around the plant invites mildew.
  • If the air circulation is poor, Powdery mildew may invade the plant.

If you do not treat the infection in time, it will spread all over the plant and disrupt its growth.

Treatment for Powdery Mildew

If your Cucumber is affected by Powdery mildew, you can take the following measures to revitalize it.

  • Mix one tablespoon of baking soda in a gallon of water and spray it on the affected parts of the plant.
  • You can also mix milk with water in a ratio of 1:9 and spray it on the plant. Repeat this treatment daily for at least five days.
  • You can also use apple cider vinegar to treat powdery mildew. To make a foliar spray, mix three tablespoons of apple cider vinegar with one gallon of water.
  • Powdered potassium bicarbonate is also incredibly effective at eliminating powdery mildew spores on plants.
  • Mix four tablespoons of potassium bicarbonate power in one gallon of water to make a foliar spray.
  • Trim off the infected parts using a sterilized pruner to avoid spreading the fungal disease.
Stunted Cucumber
Cucumber loves warm temperature, and low temperature can quickly kill the plant.
  • Do not keep the plant in temperature and humidity conditions favorable for fungus to develop.
  • Keep the plant in sunlight and make sure the plant has proper air circulation.
  • You can use chemical options like Bonide and Dr. Earth fertilizers to eliminate powdery mildew.
  • You can use fungicides containing copper sulfate and hydrogen peroxide to eliminate powdery mildew.
  • You can also use Neem oil to treat powdery mildew.

3. Repel Pests

Pests are one of the reasons why the leaves in your Cucumber may exhibit tiny white spots.

Different pests like mealybugs, scales, whiteflies, and aphids attack the plants, feed on their sap, and leave them looking pale and white.
Ladybugs in plant leaf
Ladybugs can devour the aphids from your Cucumber plant.

These pests are attracted to the Cucumber plant thanks to its juicy leaves and poor growing conditions.

Although mealybugs, scales, and whiteflies are not technically spots on plants, they appear as patches and spots when seen from afar.

Aphids suck the saps and juices from the plant’s leaves and stem and leave them withered, pale, and white.

Treatment for Pests in Cucumber

  • Discard the parts that pests have already damaged.
  • Keep other plants away from your infected Cucumber to avoid transferring pests.
  • Apply isopropyl alcohol to the affected regions by dipping a cotton ball into it and rubbing it on the leaves.
  • You can also spray neem oil on the foliage to eliminate different pests.
  • Some pests can be manually removed using the blunt edge of a knife.
  • Ladybugs are natural enemies of Aphids. So you can attract them to your plants.
  • You could use Garden Safe and Ortho Max if you sought chemical options.

4. Provide Enough Sunlight

The Cucumber plant needs 6 to 8 hours of sunlight daily for optimal growth and fruit production.

Lack of sunlight prevents the plant’s leaves from producing chlorophyll, which causes the plant’s leaves to become whitish and pale.

As fungal diseases thrive in shaded areas, providing ample sunlight can ward them off and produce a high-quality cucumber.

If sunlight is inadequate, you can also place your plants under full spectrum LED grow lights for 16 to 20 hours per day.

If your garden Cucumber is not getting enough light, you can remove the shade between the light source and your lawn; or, even better, replant it in a sunny location.

Lack of light also induces other symptoms like yellow leaves, lack of fruit, stunted growth, etc.

Treat white spots on cucumber leaves
Summary of how to treat white spots on cucumber leaves.

Tips for Preventing White Spots on Cucumber Leaves

Look below for the tips to remove the white spots on your Cucumber Leaves.

  • Always keep the leaves of your Cucumber clean so that diseases and pests cannot attack it.
  • Do not overfertilize your plant, as it may also invite problems.
  • Always be wary of your Cucumber’s watering and sunlight needs.
  • Make sure there is proper airflow around your Cucumber plant.
  • Plant your Cucumber seeds at least 8 to 12 inches apart for better aeration, and thin them out once they grow into seedlings.
  • Use well-draining, fertile soil with a pH ranging from 6.0 to 6.8.
  • When purchasing Cucumber plants, look for varieties resistant to powdery mildew. If a Cucumber’s seed packet displays PM, it is resistant to powdery mildew.
  • Provide nutrition to the soil by occasionally mixing organic nutrients with it.
  • Mulch the top of the soil during colder months after harvesting the Cucumber vegetable.

To Conclude…

The Cucumber plant has been around for a long time as people’s favorite salad.

Many of us prefer to grow Cucumbers in our homes. So, if you want the same, you need to be on the watch for the diseases and anomalies your plant can incur.

Always remember that preventing white spots is a lot better than treating them.

Happy Gardening!

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