How to Treat White Spots on Cucumber Leaves?

The Cucumber plant is an edible vegetable that provides a lot of nutrients. Keeping this in mind, I got a plant for myself.

But to my despair, I noticed white spots on my Cucumber leaves as they grew. And I had to eliminate them.

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.

Cucumber leaves white spots
White spots on Cucumber leaves are mainly caused by powdery mildew.

If I had known these from the beginning, I would have prevented white spots on my Cucumber leaves.

If you incurred the same problem, do not worry, you have landed on the right page.

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

Is It Normal for Cucumber Leaves to Have White Spots?

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

Forget the aesthetic beauty boosted by the white spots on the leaves. Focus on how dangerous they can be for the plant in the long run.

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

White spots on cucumber leaves
White spots on Cucumber leaves may signify powdery mildew, lack of sunlight, overwatering, or pest attack.

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 may not sound as dangerous as they are. They hinder the normal growth of the plant and end up killing it.

It may also affect the yield of Cucumber, the tasty and juicy salad you wait to devour with your food.

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)White powdery-spots on the leaves
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 ShockDifferent brown or black spots on leaves
Leaves start drooping
Lack of SunlightLeaves turn yellow, no fruit and flower production
OverwateringDamaged roots, yellow leaves, limpy and stunted growth of plant

Understanding what caused the white dry spots in your Cucumber leaves is important before jumping to the treatment measures.

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

1. Provide Adequate Watering 

Overwatering is a major contributor 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.

Watering Cucumber
You should water the Cucumber plant and keep the soil moist most of the time.

The crunchy Cucumber is 95% water, so if you do not fulfill its watering requirement, you will end up killing it.

That said, you should not also overwater it. Though it may not pose as much threat as underwatering, it still is pretty dangerous.

Due to too much water, the Cucumber 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 main 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 the 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 tbsp 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 stems and leave them withered, pale, and white.

Getting rid of the pests is important before they do any grave damage to the plant.

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 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

Sunlight is an important factor for the better growth of any plant, as they need sunlight to perform photosynthesis.

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

Cucumber in sun
The Cucumber plant needs somewhere from 6 to 8 hours of sunlight to flourish properly.

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.

So, if you have placed your Cucumber pot in a shady area, move it to a place where it can get the required sunlight.

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.

Tips for Preventing White Spots on Cucumber Leaves

Although white spots on Cucumbers are not entirely incurable, you must be extremely fortunate to be able to treat them.

So, when it comes to these white spots, it is always better to prevent them altogether.

Look below for the prevention tips.

  • 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.
Young Cucumber Plant
Plant the Cucumber plant in well-draining, fertile soil, and you will never be disappointed.
  • 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.

From the above information, you must have deduced that caring for the Cucumber is not a hard task. So, go for it!


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!

If your Cucumber plant has suffered from other problems, like overwatering damage and yellow leaves, consider reading our articles. 

Leave a Reply

Your email address will not be published. Required fields are marked *

You May Also Like