There are many reasons behind yellow cucumber leaves. These could include disease, pest attack, water levels, light, or nutrient deficiency. We are here to explain why this happens and the best solutions to prevent it.

Cucumbers are a popular plant for home gardeners to grow. They are tasty, nutritious, and great for the summer season. Although cucumbers are simple to grow, they can become susceptible to many problems. When these issues become more severe, the vegetable gets dry faster.

Why Are Your Cucumber Leaves Turning Yellow?

Cucumber plants yellowing is not a minor issue. In some cases, the plant may die before producing fruits.

Below are some reasons you might see cucumbers with yellow spots:

1. Light

Light can be the main reason behind yellow cucumber leaves. Whether you’re growing indoors or outdoors, make sure they are getting enough sunlight. Cucumbers need six to eight hours of sunlight daily.

What to Do?

  • Shift the cucumber plants to a location where they will get six hours of light.
  • If you are growing cucumbers indoors, use LED supplementary or fluorescent lighting.

2. Water Levels

Your cucumber plants must have the right amount of water. Overwatering or underwatering can be quite problematic for your cukes.

Overwatering results in a lack of oxygen in roots. This also makes cucumber leaves turn yellow and start wilting.

Insufficient water can also be responsible for yellowing leaves on cucumber plants. Remember, the plant requires one to two inches of water every week.

What to Do?

  • Water your cucumber plants on a regular basis.
  • Grow cucumbers in raised beds to get rid of yellow cucumber leaves.
  • In case of drainage issues in soil, try loosening it by mixing in some sand.
  • Use handy gadgets to measure the soil moisture. It can also prevent over – or under-watering your plants.
  • Insert your finger two inches into the soil and find out if it’s dry. If it feels dry, it’s time to water your cucumbers.

3. Chlorosis

Chlorosis is a condition that causes plant leaves to produce insufficient chlorophyll. As you know, chlorophyll is the green leaf pigment that grabs sunlight to fuel the production of food. Thus, without enough chlorophyll, cucumber starts turning yellow and starving.

What to Do?

  • To figure out why chlorosis is happening, study your cukes for other clues.

4. Pests

Pests are also one of the reasons behind cucumber leaf discoloration. Common pests that attack cucumber include potato leafhoppers, spiders, aphids, mites, or whiteflies.

a) Spider Mites

Spider mites, whether adults, nymphs, or larvae, can wreak havoc on your cucumber plants. They damage the leaves by sucking the sap from them. These insects stay on the underside of leaves, where they leave a fine silver web.

Mites appear in late June through August. They are more widespread in dry and hot weather. Adult spider mites are very small (around 1/50 inch). They have yellow to dark crimson coloring.

Feeding marks display as light dots on the leaves. As the feeding progresses, you’ll see yellow cucumber leaves. In worst cases, it may dry out and fall off.

What to Do?

  • Avoid stressing your plants or creating dusty or dry conditions.
  • Use clove, garlic, neem, or rosemary essential oils on the cucumber plants. Spray insecticidal soap when you first spot mites to keep these unwanted bugs away.
  • You can even eradicate the leaves from the bottom of the plants.
  • Spray cucumber plants with an appropriate solution until it starts dripping from leaves.
  • Use row covers over the plants’ leaves during the start of the season

b) Whiteflies

An infestation of whiteflies can also lead to yellow cucumber leaves. Several species of whiteflies can attack cucumbers. Greenhouse and Silverleaf varieties cause the majority of destruction. They are usually found on the underside of leaves as they love to feed on sap.

What to Do?

  • Shake your cucumber plant.
  • Use row covers and reflective mulches.
  • Do not plant cucumbers at a time which coincides with peak levels.
  • In case of a severe infestation of cukes with whiteflies, discard and dispose of them in sealed bags.

c) Aphids

Sometimes, your cucumbers suffer from aphid infestation. These little bugs can cause them to become stunted and mottled. Aphids are small oval insects with a long mouth.

These yellow and green insects suck the fluids out of plants. They are often challenging to control. That is why it is pivotal to get rid of these tiny insects early. Cucumber leaves bent downwards at the edges have likely been attacked by aphids.

What to Do?

  • Apply a forceful spray of water where they are present.
  • Spray neem oil or use insecticidal soap on aphids or underside of cucumber leaves.
  • Place aphid enemies, such as green and brown lacewings, ladybugs, hoverflies, midges, bigeyed bugs, damsel bugs, soldier beetles, or blister beetles in your garden to prevent yellow cucumber leaves.
  • You can also use insecticides like Diazinon or carbaryl. However, it’s important to avoid using these in high temperatures to prevent the burning of leaves.
  • Avoid planting cucumbers near weedy areas or woods.
  • You can even plant a cornrow on the windward side of the plants.
  • Avoid using more nitrogen fertilizer than necessary.

d) Potato Leafhopper

The potato leafhoppers are insects much larger than the bugs mentioned already. They stay on the leaves of cucumbers to suck the sap out of them. As they feed, they inject toxins. This makes the leaves weak and turns yellow.

Once the leaves get too much damage, they fall from your cucumber vine. This can also hinder the production of cucumbers. Moreover, these pests also leave behind a sticky substance known as honey crew. It causes sooty mold to develop.

What to Do?

  • After you spot nymphs, apply an insecticide as soon as possible.
  • Spray plants with powerful blasts of water from a hose.
  • Cover all the yellow cucumber leaves and stems with insecticidal soap. Hang sticky traps or double-sided tape around your infested cucumber plants.
  • Shield cucumber plants using row covers or screens.
  • Shake the plants to get rid of adult potato leafhoppers.
  • After the growing season, drop dead material from your plants and dispose of it.
  • Encourage insects like ladybugs, minute pirate bugs, or lacewings. They will fend off the potato leafhoppers in no time.

5. Plant Diseases

Bacterial and fungal diseases are often responsible for yellow spots on cucumber leaves. They will also lead to the death of plants. Common cucumber diseases include the following.

a) Mosiac Virus

The mosaic virus affects more than 150 plant varieties, including cucumber. They live in the soil, so they can keep infecting other plants throughout the year.

This virus causes cucumber leaves to wrinkle or curve downward with yellow or brown spots. If you leave your infected plants in the garden untended, the virus will spread via leafhoppers and aphids.

What to Do?

There is no way to treat plants infected with the virus. All you can do is…

  • Get rid of the infected yellow cucumber leaves or plants as soon as possible to prevent spread.
  • Avoid planting Cucurbitaceae family plants where you have your cucumber plants.
  • Destroy or drop diseased plants as soon as you spot the virus. Make sure you wash your hands using water and detergent.

b) Verticillium Wilt

This is a wilt disease caused by six species of Verticillium fungi. The pathogen can survive in the soil for as long as eight to 10 years. You can notice the symptoms on only one side of the cucumber.

c) Downy Mildew

Downy mildew is one of the most destructive foliar diseases. Pseudoperonospora Cubensis causes it. The telltale signs include yellow spots on the cucumber leaves and gray mold underneath. These spots turn brown later on.

Remember, humid and cool conditions encourage the development of this plant disease.

What to Do?

  • Boost air circulation around your plants using trellising.
  • Keeping your garden free of debris will help fix the yellow cucumber leaves problem.
  • Apply systemic or contact fungicides early to stop the progression of the disease.
  • Try to keep cucumber leaves dry using drip irrigation or wide row spacing.
  • Discard infected plants.

d) Fusarium Wilt

Fusarium wilt is a ground-dwelling disease caused by the Fusarium oxysporum f. sp. cucumerinum. This fungus can thrive in the soil for long periods. It causes cucumber leaves turning yellow around edges and then inwards. The virus develops on older cucumber plants and leaves.

What to Do?

  • Remove the infected plants and debris immediately.
  • Guard your cucumbers with lightweight row covers to restrict future outbreaks.

e) Anthracnose Leaf Spot

Colletotrichum Orbiculare fungus causes Anthracnose. The pathogen can attack all types of cucurbits, but they target cucumbers, watermelons, and muskmelons. Anthracnose infection starts with irregular water-soak leaf spots. These spots turn yellow and then change to brown color.

This disease develops in moist and warm environmental conditions.

What to Do?

  • Get rid of the infected cukes, seed, and plant debris immediately.
  • Allow a lot of space between the plants.
  • Prune weeds and extra cucumber leaves frequently.

6. Nutritional Deficiency

Cucumbers also need many nutrients to thrive and grow. When they are not getting enough of these nutrients, chlorosis occurs. To determine whether your plant is nutrient deficient, get your garden soil tested.

Below are the common deficiencies that can cause yellow cucumber leaves.

a) Nitrogen

Nitrogen is a crucial nutrient for cucumber plant growth. Leaves will turn yellow at the tips and along the central veins due to decreased nitrogen levels. Nitrogen deficiency also inhibits plant growth.

What to Do?

  • Buy high-quality soil fertilizer that features the proper dilution rate.
  • Add a two-inch compost layer to increase the nitrogen content
  • Add one tablespoon of ammonium nitrate when you spot the cucumber flowers blooming. You can add it to the soil again three weeks later.

Note: Always follow instructions on your fertilizer. Avoid using too much fertilizer in the soil to prevent plant reproduction.

All these tips will prevent cucumber leaves from turning yellow.

b) Phosphorous

Do you see bronze or deep yellow cucumber leaves? If yes, this indicates a phosphorous deficiency. Phosphorus is vital for the normal development of reproductive organs and roots. Its deficiency can stop fruit production and hinder growth. Phosphorus-deficient plants are stunted and have weak roots.

What to Do?

  • Supplement your soil with fertilizer on a regular basis.
  • Perform a soil test to establish the phosphorus status of the soil.

c) Potassium

The potassium deficiency in cucumber first occurs on older leaves. They make cucumber leaves turn yellow at the edges and tips. After that, it spreads between the primary veins towards the center of the leaf.

Young leaves tend to look dull and small. Cucumber fruit appears narrow at the end of the stem. It gives the fruit a club-shaped appearance.

What to Do?

  • You can use a well-balanced fertilizer to feed your cucumber plants to eliminate the issue.
  • Treat soil for alkalinity or acidity.
  • Bury citrus rinds around the affected cucumber plants.

d) Zinc

Zinc deficiency causes cucumber leaves to turn yellow and droopy. Leaf size also gets very small. Moreover, it blocks the cucumber’s growth.

What to Do?

  • The simplest way to solve this issue is to spray zinc sulfate solution or organic kelp.

e) Iron

Iron deficiencies cause young cucumber leaves to develop interveinal chlorosis. This is the yellowing with green veins, but the older leaves stay green.

What to Do?

There are two ways to fix it: either treat the soil or the cucumber plants.

  • You can spray liquid iron on the foliage of the plant.
  • To treat the soil, use chelated iron either in powdered or granular form.

Note: You can even do a soil pH test and amend it to get it below 7.

f) Calcium

When cucumber grows under humid conditions, they can also get calcium deficiencies.

Other factors can include…

  • Soil salinity
  • Waterlogging
  • Root diseases
  • High supply of potassium or ammonium

You can spot the deficiency in the young and growing leaves with low rates of transpiration. Growing leaves look distorted and may cup downwards. Calcium deficiency also causes yellow cucumber leaves to be tasteless.

What to Do?

  • Limit the use of ammonium-based fertilizers.
  • Apply lime to acidic soils.

g) Magnesium

Magnesium deficiency causes older cucumber leaves to turn yellow and cause veins. In case of severe deficiency, a light tan burn will occur in the yellow areas. It also reduces fruit yield.

What to Do?

  • Apply sprays of soluble magnesium nitrate.
  • You can also spray Epsom salt solution to treat your yellow cucumber leaves.

Conclusion

Growing cucumbers at home allow you to have this crunchy treat available year-round. Cucumber leaves turning yellow and dying shows that something is wrong with plants. It can happen to every gardener from time to time.

By implementing our tricks, you can save your vine crops. When dealing with cucumber plant problems, talk with a skilled local agricultural specialist. The expert can offer you more tips to treat yellow leaves on cucumber plants.

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