Cucumber Leaves Turning White? (How to Treat and Prevent It)

Ryan Womeldorf
by Ryan Womeldorf

Growing vegetables in a garden is a simple way to get fresh veggies. Growing certain things is a relatively easy endeavor, too. Even still, there are certain things that can impact things like tomatoes and even cucumber plants.

If you notice that the leaves of your cucumber plants are starting to turn white, there are a few probable causes. It could be due to powdery mildew, another type of disease, or even a pest issue. Resolving and preventing the issue is pretty easy as well.

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Cucumber Leaves Turning White at the Edges

If you happen to notice that the edges of your cucumber plant leaves are turning white, it is most likely powdery mildew. Powdery mildew is a fungus and typically starts by attacking the leaf edges at the start of its infestation.

If nothing is done to stop its growth, those spores will continue to work their way through the leaf until it is completely white. Even the smallest of spots will grow and eventually merge with one another. If left unchecked, powdery mildew can even cover the stems and stalks as well.

Sunlight prevention. White fungal spores will not necessarily spread to the actual cucumbers. While that may seem like good news, there is a “but” involved. In the more advanced stages, those powdery spores can prevent sun from getting to the foliage. When plants can’t go through photosynthesis, growth can be stunted.

Should the problem go on long enough, your cucumbers will suffer. Stunted growth will mean smaller and fewer cucumbers of a poorer quality.

White Spots After Transplanting

Have you recently transplanted your cucumber plant from another area of the garden? It is important to know that a lot of plants go through what is known as “transplant shock.” Transplant shock happens immediately in the wake of the cucumber plant being transplanted.

Transplant shock will generally only cause a temporary slowdown in the growth of the plant. If the leaves are turning white in the wake of a transplant, however, there is a bigger problem to be aware of.

Stem or root damage. Should you notice that your cucumber plants are starting to show white splotches or white coloration in the leaves after transplant, it could be a sign of stem or root damage. The most likely cause is the aforementioned powdery mildew, however, so replace the soil.

Fungus will remain in the soil during the winter months before attacking any new plants in the area. So, if you notice that plants grown in the same spot tend to get white spots, fungus is the issue. Dig up and replace the soil in that area to avoid repeating history.

Cucumber Seedlings Turning White

Planting seedlings in your garden is a new beginning. Make sure that you plant your seedlings with as much a success of chance as possible to promote seedling development and germination. You make think that everything went well when the seedlings suddenly look white.

Properly growing and developing cucumber plants should look a healthy green color. When they turn ghostly white, it is a strong indication of fungus growth. The most common problem is a re-use of soil where the fungus has previously grown. Whenever putting a new seedling in, use fresh soil if possible, to avoid spreading fungus from plant to plant.

Pests Could Be a Reason

You may find that tilling and replacing the soil yields no progress. If you can be reasonably certain that there is no fungus at play, the real reason may be due to a pest problem.

Leafhoppers. In particular, leafhoppers tend to be the most annoying for cucumber plants. These wedge-shaped, small insects generally appear to be either green, yellow, or brown in color. They feed by puncturing into the leaf of the cucumber and then sucking out the fluids within.

Continuous feeding on the cucumber leaves can lead to those little white specks that you see near the upper surface of the leaves. When feeding is allowed to persist, the leaves can dry out. In some cases, the ends of the leaves can even look burned.

Get rid of the pests. The good news is that these pests don’t require any type of chemical treatment. The reason being that their feeding activity doesn’t result in any real long-term damage. To keep them from getting to the cucumbers, drape a few floating row covers over top of the plants. When the flowers start to bloom, remove the covers so that any pollinating insects are able to securely reach the blossoms.

Improper Cultural Control Can Play a Key

Sometimes it may not be a matter of fungal spores or even pests wreaking havoc. Improper spacing and cultural control can be enough to turn those cucumber leaves white, too.

Sunlight. Cucumbers need proper sunlight in order to develop and grow properly. Keeping them in too much shade can rob them of sunlight. They do well in sunlight and those fungal spores will not survive in direct sunlight.

Proper spacing. While it may seem like an arbitrary thing, proper spacing is key to proper cucumber growth. Without proper spacing, the plants don’t have the necessary circulation. And since fungal spores thrive in dark, cool, damp places, that is precisely what they hope for.

Make sure that you plant your seeds at least an inch apart and then thin the seedlings so that they have about 12 inches of space between each of the plants. Proper air circulation helps to keep fungus at bay.

Water stress. Overwatering is another contributing factor to white cucumber leaves. Water stress leaves the plants less able to fight off those fungal pathogens. Make sure that you irrigate slowly on a weekly basis so that the top 6 or 8 inches of the soil gets moist.

Make sure to water your cucumber plants in the morning to give the foliage the time it needs to dry prior to the evening. Remove any debris at the end of the season to prevent pests and fungal spores from overwintering within your garden.

How to Get Rid of White Powdery Mildew

The good news is that it is relatively easy to get rid of those white powdery mildew spots. All it takes is a little DIY concoction to get the job done. The mixture is nothing more than water, vegetable oil, and baking soda and you have an effective fungus combatant.

Step 1: Create the mixture.

Start by mixing in a teaspoon of baking soda with about 2 liters of water in a spray bottle. Shake the mixture up well and then add 4 drops of the vegetable oil. This will help your mixture stick to the leaves of the cucumber plant.

Step 2: Spray.

With your mixture ready, it is time to spray the leaves when you first see the white spots. Make sure that you not only saturate the leaves but the surrounding soil as well. You will need to do this once a week or so until the white disappears.

Step 3: Non-organic alternatives.

There are also several different brands of commercial fungicide that will get the job done. It all depends on your preference and comfort level mixing the DIY cocktail.

Step 5: Start from scratch.

Should you be dealing with white fungus regularly, you could start over. Dig up the plant, till and replace the soil, and start again. Sometimes fungus can get thoroughly embedded in the soil and won’t go down without a fight. Starting from scratch can ensure that the issue is dealt with for good.

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How to Prevent Powdery Milder on Cucumber Leaves

While there are a few easy solutions, nothing is better than prevention. After all, not having to deal with the problem should be the goal. Thankfully, there are a few helpful suggestions to ensure that your cucumber plants grow in a healthy, undisturbed manner.

Step 1: Use mildew-resistant strains.

There are actually mildew and fungus-resistant strains of seed out there that will fight the fight for you. That doesn’t mean they are immune, but they should drastically reduce the chances that fungus will attack your plants.

Step 2: Reduce your numbers.

What you may not have realized is that cucumber vines are quite heavy producers. For instance, just two healthy, growing cucumber plants should keep the average family flush with cucumbers throughout the summer.

Those who enjoy making their own pickles would benefit from 4-6 plants. Just a few well-spaced cucumber plants will wind up being far more productive than a bunch that grow much too close together.

Step 3: Implement proper spacing.

Remember, spacing is one of the essentials for growing cucumber plants that will thrive. Cucumber vines can grow from 6 to 10 feet in length and will have multiple runners that go along each main vine.

The vine leaves are petty large. Without the proper spacing and a trellis for the vines to climb, you can be dealing with a twisted mess. Moreover, you would be losing that all-important circulation that your plant needs.

Step 4: Ensure proper sunlight.

The proper amount of sunlight can be tricky. They need plenty of sunlight but not so much that they wind up burnt. Find a spot where there is plenty of light but not constant direct exposure to the sun.

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Ryan Womeldorf
Ryan Womeldorf

Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.

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