Why Are My Cucumber Plants Turning Yellow? Know All Problems And Troubleshooting

Cucumbers are something that almost every person admires. They play a vital role in your salad bowl during summers. There are so many different ways to consume these scrumptious vegetables as cucumber soup or cucumber salad. This plant usually produces a plentiful harvest on sprawling, tall vines every year. Some cucumber varieties grow on bushy, compact plants along with flat leaves. So, are your cucumber plants turning yellow for no reason? If so, then keep on reading!

Everything seems perfect until you discover your cucumber leaves turning yellow. It definitely begins to worry you. On average, growers can begin to pick their first cucumbers as early as 55 days following the plantation. However, there are several problems that spate cucumber plants. One should not ignore these problems as it could lead to a severe situation, where your yellow cucumber plant could even die. So, let’s know about some of the most common problems behind why cucumber leaves turn yellow.


Why Are My Cucumber Plants Turning Yellow?

Cucumber plants produce a plentiful crop of appetizing fruits throughout summers on expansive vines or bushy plants with flat and large leaves. However, cucumbers are vulnerable to a variety of problems. Some of these problems cause cucumber leaves to change their color to yellow. If the condition is too severe, it could result in the death of the plant. Have a look at some of these diseases right below!

Smaller Pests

Smaller pests could be the most common reason behind why your cucumbers leaves turning yellow. They might be sucking the sap from your cucumber leaves. These common smaller pests include spider mites, whiteflies, and aphids. So, all of them could result in turning your cucumber plants yellow.

Smaller Pests

Here, spider mites result in the leave stippling as these mites suck the cucumber leaves. One can spot these mites on the leaves’ undersides. Next, whiteflies are usually white-winged or tiny insects. These flies reside under the leaves’ undersides. They fly if you happen to disturb the plant. Aphids are oval-shaped and tiny insects that cause your cucumber leaves to turn yellow. They also house under the leaves’ undersides. They leave behind a sticky substance that resembles black mold.

To treat smaller pests, growers can take the help of insecticidal soap. One can apply this treatment every week or after two weeks. You should not spray this soap during high temperatures. Before you spray this soap, it is recommended to read the instructions on the package. You have to eliminate the yellow leaves from the plant depending on the infestation’s severity. Usually, cucumbers can manage a tiny infestation but it will kill your plant if there is an infestation on large scale.

Potato Leafhopper

Certainly, you may not have heard of potato leafhoppers before. These leafhoppers like to feed on cucumber plants, where they suck the sap from the plant leaves. Potato leafhoppers inject toxins into the cucumber leaves while they continue to feed. This makes the cucumber leaves turn yellow instead. As time passes by, the yellowed leaves will drop off from the cucumber plant.

Potato Leafhopper

To stop these potato leafhoppers, you can spray insecticides. Be careful while spraying out chemicals on your plants that produce food. Another method to keep away the insects is to manage all the weeds present in the growing area. Hence, you can employ some row covers to stop these insects from coming over the area.

Moreover, the University of California Integrated Statewide Pest Management Program suggests using cultural methods instead of insecticides. Plus, you need to manage the weeds in the place and then, employ row covers to prohibit these insects.

Nitrogen Deficiency

Another common reason behind why cucumber leaves turn yellow is the deficiency of nitrogen. This deficiency leads to yellowing or pale leaves that stuns the plant growth. Nitrogen deficiency can even kill the cucumber plant if severe. One can fix this deficiency very easily. As you know, cucumber plants need fertile soils as they tend to be heavy feeders. If there is a deficiency of nitrogen or phosphorous, the foliage and vines become yellow.

cucumber leaves turning yellow

For treatment, you need to but a 6-10-10 fertilizer. Here, every plant must receive 1-2 tablespoons of the fertilizer. Growers can even put in 33-0-0, ammonium nitrate after three weeks or when the flowers start to bloom. However, do not put too much of this fertilizer as it stops your plants from producing any fruit.

Another effective way to add nitrogen to the cucumber plants is by adding mulch all around the base. If you own a lawn, then grass clippings would be free. When they decompose, they emit out nitrogen into the soil. Meanwhile, the clippings will stink as they decompose. However, it is a free source to produce nitrogen.

Here’s a tip for applying the fertilizer. Before you add it, it is better to get a test of the soil from any local lab or county extension agency. By doing so, you will have an idea of what all nutrients exist in your soil. It is a great way to control and monitor the quantity of fertilizers you need to add to the garden.

Phosphorous Deficiency

If cucumber leaves turning yellow or bronze, it indicates the deficiency of phosphorous. This deficiency prevents the production of fruits in the plant. The effective way to make sure that this deficiency does not arise is to modify the soil with well-rooted manure, compost, or cover crop before you plant the seeds. As per the U.S. Department of Agriculture, the hardiness zones for cucumber plants are 2 through 11. Also, the growth of cucumber plants depends on the quality and amount of nutrients they accept. Many nutrients need to be set in the soil before you plant the cucumber seeds.

You can even amend the soil with the help of 6-6-10 or 4-8-5 fertilizers. These fertilizers are easily available at garden centers and hardware stores. Before you plant cucumbers, apply one or two tablespoons of the fertilizer each mound.


Unfortunately, cucumber plants are prone to lots of fungal and bacterial diseases. These diseases can kill the plant rapidly. Out of all diseases, the most common ones are the mosaic virus and verticillium wilt. Know about other common diseases in this section if your cucumber plants turning yellow some time!

cucumber diseases

Verticillium wilt: Verticillium wilt is a kind of soil-borne fungus. During this disease, you will notice light brown stripes on the plant stem. It is very common among places where you have planted plants like tomatoes, eggplants, peppers, and potatoes once.

Mosiac virus: Mosaic virus enables the cucumber leaves to clot and turn brittle. Here, the plants stun to poor yields. This virus spreads from one plant to the other through leafhoppers and aphids.

Unfortunately, one cannot treat these kinds of disease in any way. If your cucumber plant gets infested, you need to eliminate that plant as soon as possible to eradicate the disease. In the following season, do not grow any melons or squash in that place as these diseases live in the soil and can infect other crops.

Apart from these two diseases, there are plenty of others:

Fusarium wilt: Apart from verticillium wilt, there is fusarium wilt. This fungal disease infects the vascular tissues of the plant. These fungal spores reside in soil, which are carried further through cucumber beetles. To treat this, eradicate and demolish the infected cucumber plants. For these kinds of diseases, fungicides do not work effectively.

Alternaria Leaf Blight: The disease affects cucumbers and melons. These fungal spores are carried out through wind and even spread through infected water and soil. Warm and wet situations favor this disease. It survives over winters in debris so as to attack the cucumber plant all over again in springs. To treat this fungal disease, you need to use fungicides. However, keep in mind that fungicides make the cucumbers inedible.

Anthracnose: It is another kind of fungal disease, which is prevalent in warm and wet weather conditions. Southern regions having higher humidity are more prone to this fungal disease. This fungus lies dormant in fallen leaves, vines, and debris while releasing spores in springs to contaminate new plants. Use fungicides to treat this disease.

Southern corn rootworm: Small plants even turn yellow when infected by southern corn rootworm. This worm is the speckled cucumber beetle’s larvae. To prevent this disease, cultivate your soil prior to planting so as to expose the larvae.

Squash Bug: When your cucumber leaves exhibit yellow specks, which turn to brown and then, black, the reason could be a squash bug. This bug is a shield-shaped, flat brownish and blackish bug that features a triangular back. It sucks the juice from cucumber plants. For treatment, trap these bugs underneath the boards and destroy them.

Mildew: There are various kinds of mildew. In cucumber plants, you will find mildew like downy mildew and powdery mildew. As its name suggests, powdery mildew resembles a powder. If you come across flour-like substance on leaves, eradicate them and cut down the water supply. This kind of mildew thrives in water. Meanwhile, downy mildew causes brown surfaces on the leaves. It is a type of fungus. As this fungus thrives in debris, it is better to clean your garden.

Watering and Feeding

If none of the above-mentioned causes made your cucumbers leaves turning yellow, there can be other factors that can be resolved pretty quickly. As you know, cucumber plants are thirsty plants. If there is scarce in watering, the cucumber leaves will suffer in the first place. The leaves become yellow and then, descend toward the earth.

watering cucumber plants

On the other hand, if there is a hard or dense soil around the cucumber plant, you need to break it using a trowel a little bit. While carrying out this task, bear in mind not to hurt the roots. Meanwhile, excess water can also cause the root to decay. If that’s the case with you, decrease the watering or try to water a bit far from the cucumber plant.

So, this is all about the causes due to which cucumber leaves turn yellow. Examine your cucumber plant closely in order to find out about the most relevant cause. Sometimes, these leaves turn yellow just because of the wrong watering pattern. Try to make changes to it and see if the problem gets resolved. If no relief, you should check out the leaves for the causes mentioned here. It is important to recognize the real problem. If you delay more, you may lose your plant forever.


Now, you know why your cucumber plants turning yellow. There are various reasons for the same. Here, we have listed some of the common reasons why your cucumber leaves turn yellow. Once you spot yellow cucumber leaves, you need to find out the accurate reason why cucumbers leaves turning yellow. To find out, you have to carry out an extensive inspection of the cucumber plants. Check out your plants and notice any signs.

Do not forget to turn the cucumber leaves over to examine the bottom. This is important as most pests hide under the leaves’ undersides as they destroy the plant. If you are still unable to locate any pests, try to relate some signs to a potential cause. If you identify the real cause quickly, you have the chance to save your plant from dying. In addition, you could enjoy scrumptious cucumbers!

Hope, you find all the answers to your queries regarding why your cucumber plants turning yellow. If you still have any query or question, do not hesitate to share some with us. We would try to resolve them as early as possible. Post your comment in the comment section below! We would love to hear from you.

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