Why Cucumber Leaves Turn Yellow and Die | Expert Guide


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Well! If you notice that your cucumber leaves are turning yellow, only one thing indicates that your sick cucumber plants need your attention. Your cucumber plant loses its green color; its leaves had become paled and got a disease called Chlorosis because it lacks chlorophyll. As chlorophyll is a part of photosynthesis, it converts sunlight into chemical energy, and its deficiency affects the cucumber plant’s overall health. So in this topic,why cucumber leaves turn yellow and die, we will discuss some reasons by looking at the factors.

The reasons for the yellowing of leaves are many. Here are the details of these causes for all those out there looking for solutions:

Plant Pests

You must have noticed a variety of different insects on your plants, but some are very harmful to the plant’s health because they suck the sap out of the leaves.

This is the common reason for the leaf discoloration that turns them yellow. 

  • Aphids are small oval-shaped insects hanging on the underside of leaves.
  • Their color is green and yellow and leaves behind a sticky residue called honeydew.
  • Spider Mite is another insect, sucks on the cucumber leaves and causes yellow stippling.
  • Usually found on an infected plant, on leaf underside, where they make delicate silvery webs.
  • Whiteflies are another type of insect, like aphids; they leave behind honeydew.
  • You can see a cloud of small white-winged shaped insects called whiteflies when you shake the leaves. 
  • On the infected plants, if you spray insecticidal spray, you can get rid of these insects.
  • More significant than another pest is a potato leafhopper, which also enjoys feeding on the cucumber plant by sucking sap from leaves.
  • They inject poison and accumulate on the leaf surface, which leads to damage and yellowing in color, and eventually, leaves fall from the plant.
  • To get rid of potato leafhoppers, you can use pesticides to kill them, but this is not preferable for plants, which you use in your food.
  • So alternative method is to keep the infected plant in the weed-free area and use net covers to keep insects away. So these are the main reasons why cucumber leaves turn yellow and die if having pest problems.
Why Cucumber Leaves Turn Yellow and Die

Why Cucumber Leaves Turn Yellow and Die: Plant Diseases

Plant diseases are the common cause of yellow leaves and yellow spots or streaks on cucumber leaves. So have a look at these diseases:

should i cut off yellow cucumber leaves

Cucumber Mosaic Virus

The mosaic virus might infect your cucumber plant if you notice that leaves are becoming wrinkled, curving downward, and have yellow spots on them.

Unluckily there is no other treatment available other than to remove the infected plants. If left as it is, the plant will die as leafhoppers and aphids carry it.

You should be careful about the disease; if it lives in the soil for a more extended period, it may harm new plants the next year. The same is the case with the next disease.

Fusarium Wilt

Have a closer look at the older leaves; if there is becoming yellow and pale, beginning from the edges and spreading on leaves from the inner side, be sure that it has a Fusarium Wilt. 

The cause of this disease is cucumber beetle larvae, as it feeds on the plant’s root.

Like the Mosaic virus, the only solution for this problem is to get rid of the infected plant. There are several options available in biological and cultural control for this fungal disease.

Moreover, another type of fungal disease is Verticillium Wilt. If your cucumber plants are grown in an area where other vegetables and fruits have already been developed, like tomatoes, peppers, potato, and eggplants, your plants might be infected.

Downy Mildew

If your cucumber plant has yellow spots on the leaves’ upper surface, which turn their color from brown afterward, be sure that it has Downy mildew disease.

These spots have a patchwork appearance and angular bounded veins on the leaves.

The grey fuzz can be seen on the leaves’ underside if there is humidity in that area where the plant is grown.

You have the down options if you want to get rid of the disease:

  • Keep leaves of cucumber dry by wide row spacing and drip irrigation, also improve the air circulation near plants.
  • Grow cucumber plants in the high resistance areas.
  • For the prevention of disease, remove the infected plants from healthy plants.
  • When the disease progresses, you should use the fungicides effective against downy mildew and plant debris.

Nutritional deficiency

Most of the diseases in cucumber plants occur due to the nutritional deficiency of several nutrients. So if you want your plant to grow properly, you should add these nutrients to its feed.

So it is a good idea to assess the deficiency of specific nutrients in the soil and solve it.

The following are the primary deficiencies, which can cause cucumber leaf disease.

Nitrogen Deficiency

If your cucumber leaf feels crispy, it may have nitrogen deficiency and affects its growth. Ultimately the baby cucumbers dying on the vine if the situation becomes severe. 

Notice that the new leaves are getting green, and older ones turn yellow along the veins and on top of tips.

Luckily, you can solve the cucumber plant problems by fixing nitrogen content in them. This adds the nitrogen content by a 2-inch layer of compost in it or ½ tablespoon of fertilizer to the plant roots. 

Another solution to this problem is to opt for ammonium nitrate; when you see the flowers are in full bloom, supply this to the plant every three weeks.

It will help if you stay careful about fertilizer quantity, as it may harm the entire plant and affect fruit production.

Iron Deficiency

If the old leaves are still greenish, and the new are yellow with green color veins, there is iron deficiency in it. You can go for a powdered chelated iron added to soil in the plant’s roots to treat this deficiency. Alternatively, you can spray liquid iron also to get rid of this problem.

Potassium Deficiency

The cucumber plants are the only plants that need a high quantity of potassium content, other than nitrogen and iron.

The young leaves become smaller in size and look dull, and also their tips become yellow from the edges. Being closer to the stem, the fruit of the cucumber plant can get a club-shaped appearance.

If you use high-quality fertilizer with potassium content can solve this problem well in time. You should also treat the soil for its acidity and alkalinity to get the best potassium deficiency results. Thus, you can solve most of the problems listed above by adding a diluted mixture of hydrogen peroxide spray on the leaves’ tops and bottoms. 

Water-related problems

If you want the healthy growth of your cukes, avoid too much watering.

Overwatering can cause oxygen-deprived roots, which leads to yellow leaves and wilting? Cucumber plants need 1 to 2 inches of water, including rainfall every week.

Loose the soil with sand if it has a drainage problem. The best solution is to grow your cucumber plants in raised beds or grow yellow leaves on cucumber plants in containers with large drainage holes.

Lack of sunlight

Another fundamental problem of yellowing leaves is that your plant may not get enough sunlight. Move your plant to that area of your garden, where it can get sunlight for 6 hours in a whole day. 

Therefore if you provide cucumber plants the right weather conditions, warm, sunny, consistent watering, and your plant will be the best of all crops. 

Why Cucumber Leaves Turn Yellow and Die: FAQ Section

How do you fix yellow cucumber leaves?

If you notice that your cucumber plant’s older leaves turn yellow between veins due to zinc deficiency, it leads to regional growth. Spraying with zinc sulfate is the best treatment for this problem. 

Why my cucumber leaves dying?

If the soil is soaked with water, it will lead to plant death due to lack of oxygen; the second reason is if the plant has a bacterial infection, the leaves will become dull and dry.

Should I cut off dead cucumber leaves?

You should cut off dead cucumber leaves and begin trimming cucumber vines by removing damaged and dead leaves. Remove older leaves so that sunlight may reach developing fruit by improving air circulation.


To end the topic, why cucumber leaves turn yellow and die, I would recommend that if you want to get the best result, you should protect the cucumber plant from insects, plant diseases, over-fertilizing, and overwatering. These are the leading causes of plant death if you take care of the plant very quickly by considering the above tips and suggestions. Therefore regular care and attention are essential for the healthy growth of the cucumber plant. Moreover, suppose you notice that the cause of yellow leaves is due to any nutritional deficiency. In that case, you can overcome this issue also by adding that specific content in the plant feed in average amounts.

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