Why are My Cucumber Leaves Turning White

When you’re into vegetable gardening, you spend a lot of time tending to your crops. All might be going well until you begin to sport some white patches on the green leaves of your cucumbers. Yes, it’s summer, but your cucumbers’ green leaves look like they have been dusted with snowflakes.

Why are your cucumber leaves turning white, what can you do to fix this issue, and what preventive measures can you take to prevent the problem in the next season. Read on to find out!

Common Reasons For Cucumber Leaves Turning White

Cucumber leaves can turn white because of four major causes: powdery mildew, iron deficiency, leafhopper infestation, and sunscald. It’s vital that you diagnose the problem early and take appropriate action to prevent loss of leaves and any further damage to the plant.

Powdery Mildew

Cucumber White Leaves causes

Cucumbers often suffer from powdery mildew disease, which is caused by the Erysiphe cichoracearum and Sphaerotheca fuliginea fungi. Typically, powdery mildew thrives in warm weather and humid environments and more so in greenhouses. It forms white, powdery spots that start at the edge of the leaves and spread quickly, causing your cucumber leaves to wither and fall off eventually.

If nothing is done to stop its growth, the small white spots can enlarge and merge until they cover the entire leaves, stalks, and stems. And although the fungal spores rarely affect the cucumber fruits, the white powdery growth hinders sunlight from getting to the foliage. It also prevents photosynthesis, which means your plant may grow slowly, defoliate prematurely, and produce smaller, poorer-quality, and fewer cukes. If left untreated, the leaves further turn from white to yellow and then withers and fall off, exposing your cucumber vegetable to sunburn.


While there are many insects that pose a threat to your cucumbers, leafhoppers are the main culprits for turning leaves white. They eat the lower side of leaves by sucking the inner content. Their toxic saliva causes discoloration of a leaf– where the leaf develops white specks.

It’s easy to tell when leafhoppers attack your cucumbers. The adults are about a quarter-inch long and easily fly away when disturbed. They are wedge-shaped, slender, and come in yellow, brown, or green, with markings.

Fortunately, you don’t necessarily need chemical treatment to get rid of leafhoppers. To keep them at bay, put up a floating cover over the top of your plants. However, remember to remove the cover when flowers start to bloom to allow insects to pollinate your cucumbers.

Iron Chlorosis

iron chlorosis cucumber leaves

This is the loss of color in plants, which is caused by nitrogen deficiency. You will notice that your cucumber leaves will start turning yellow and then white as the deficiency becomes severe. The outer edges of the leaves may also look scorched and dry as the leaf starts to die.

The dark green veins will become more visible against the loss of color, which makes it easier to diagnose the problem. Spraying iron chelates or ferrous sulfate to the soil can treat and prevent your cucumbers from dying.

Sun Scorch

This is common during spring, summer, and early fall. Exposure to too much sunlight can bleached-out patches around your cucumber leaves. Minor cases will make the leaves blister and turn pale, but affected leaves increasingly turn white with further exposure to the sun and eventually die and fall off.

Young plants are more vulnerable to sunscald, particularly when moved from indoors to outdoor or greenhouse. To prevent this problem, give your cucumbers slower exposure to direct sunlight (also known as hardening off). Try using a sunshade to protect your plants from sunburn until they toughen up.

How to Prevent Cucumber Leaves from Turning White

Prevent Cucumber Turning White

There are few easy solutions to cucumber leaves turning white, but nothing is better than prevention. True, not having a problem to deal with in the first place should be the goal. Here are tips to ensure your cucumbers grow healthy and undisturbed:

Choose Mildew-Resistant strains

Planting mildew-resistant cucumber varieties can help eliminate the problem the next season. Some popular choices:

  • Straight Eight – A vine cucumber that’s ready to pick in 60 days
  • Eureka- A deep-green fruit ready to harvest in 57 days.
  • Jackson Supreme – Compact, 20-inch pickling cuke ready to harvest in 52 days.

Space Your Cucumbers When Planting

Your garden ought to have more than 5 hours of direct sunlight and space your plants 6 feet apart. And as the plants grow, get rid of foliage to let sunlight reach the lower leaves. Lack of sunlight can cause mildew growth.

Water Stress

Avoid overwatering your plant because that can cause mildew growth. Irrigate your plants slowly on a weekly basis to ensure that only the top 6 to 8 inches of the soil gets moist.

Final Thoughts

Seeing your cucumber plants turn white is distressing, but the problem is fixable! Early detection and taking the necessary action is essential to eliminate the white matter before it kills your plants.

Related:  Are Cucumbers Melons?