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There are different reasons that lead to cucumber leaves turning yellow.
A Cucumber plant is one of the commonly grown food crops in homes thanks to its faster growth.
During the dry season one can use a garden hose to water them to avoid drying.
Even though these crops are easy to grow and take short period to mature, their leaves are most likely to turn yellow.
When the leaves start turning yellow the chances of the cucumber dying are high if the right measures are not taken.
Also read on hydrangea leaves turning yellow.
Causes of Cucumber Leaves Turning Yellow
1. Plant Pests
Pests are common even in the healthiest gardens.
You may notice some insects on your cucumber that have made the plant their home. Some insect species suck the sap from the leaves leading to discoloration and yellowing.
Common pests include:
- Spider Mites
Spider Mites take over the bottom of the leaves and suck the sap leading to yellow stippling.
If these mites are the problem, you will notice the fine silvery webbing on the leaves’ under surface.
These small insects are notorious for destroying healthy leaves and plants.
Just like the mites, they hand on the leaves’ underside and leave a sticky substance known as honeydew.
Aphids come in two colors; yellow and green.
- White Flies
White Flies, just like Aphids, leave honeydew on the leaf surface.
You will notice the white-winged insects fly away every time you give your cucumber plant a shake.
With all the above insects, insecticidal soap can help you resolve the problem.
You might need a few applications if the infestation was severe.
You can also choose to remove the infected leaves if they are not that many and leave the healthy ones to thrive.
Remove all weeds and unnecessary plants, so there is minimal surface for the pests to invade.
While pests are easy to deal with, diseases are a completely different story.
Common diseases that affect cucumber plants are Verticillium wilt and Mosiac virus. (source)
With the Mosaic virus, the leaves will have yellow spots, wrinkles, and they are downward curving.
On the other hand, the Verticillium wilt presents in the form of yellowing in the leaves that start from the edges moving inwards.
These diseases may be spread through pests, but it is also possible that they are present in the soil thanks to a previous crop.
Unfortunately, there is nothing you can do to save infested plants where these two diseases are concerned.
The best thing to do is to remove all infected plants before the infection spreads to healthy ones.
There are other cucumber diseases that are easier to deal with.
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For example, the fungal spore that manifests in powdery white spots on the leaves can be quickly sorted by removing infected leaves and avoiding overwatering.
Yellow and brown spots on the leaves may indicate downy mildew.
In this case, all you need to do is to increase the air circulation in your garden and ensure that it is debris free.
If cucumber diseases are a common problem, you should consider buying high-resistance varieties in the future.
Removing infected plants also contains the disease spread, and you can use a systematic or contact fungicide where fungal infections are concerned.
3. Water Level
Cucumber leaves will start turning yellow if you are under or over watering your plants.
This is because too much or too little water leads to oxygen deprivation in the roots, and if not resolved, the cucumber plants may die.
Once you adjust the water levels, your cucumber plant will appear healthy in no time at all.
With the use of an expandable hose you can water your crop effortlessly.
You should consider growing your cucumber on raised beds or introducing sand in your garden if the soil’s drainage is the problem.
If you find it hard to determine what amount of water is enough, get a gadget that makes it easy to measure the soil’s moisture content.
With the moisture content in mind, you can come up with a watering schedule that will ensure that your plants get one or two inches of water every week.
Some plants, like cucumber, require a lot of sunlight to thrive.
If your cucumber plants are not getting at least six hours of sun every day, they may start to yellow, and the leaves will be droopy.
No matter how frequently you water and nourish the cucumber, you will not get great results if the light is inadequate.
The plants will start yellowing, and things can only go downhill from here.
In case you are using artificial light, ensure that you provide enough of it so the cucumber leaves can turn back to their original color.
You may also move your potted cucumber plants to an area that enjoys more sun exposure if the weather allows.
There are many ways to treat deficiencies, depending on the nutrients that are missing. Common deficiencies that may lead to the cucumber leaves turning yellow include:
- Nitrogen Deficiency
Nitrogen deficiency will stunt the plant’s growth in addition to turning the leaves yellow.
If severe, the plants will eventually wither and die.
This problem can be resolved by adding nitrogen-rich soil fertilizer.
You have to be careful when applying this fertilizer as a slight mishap may be damaging to your plants.
Organic fertilizers work best for cucumbers. Add a layer or two of compost for a dose of natural nitrogen, and your cucumbers will thank you for it.
- Potassium Deficiency
Cucumbers are among the few plants that need more potassium than nitrogen.
When there is a deficiency, you will notice that the cucumber leaves are yellowing at the tip and edges.
You will also notice that young leaves are cupped, dull, and puckered.
The cucumber plants will be club-shaped in case of a potassium deficiency as the fruits will be narrower towards the stem.
This problem results when there is too much sodium, nitrogen, or calcium in the soil.
You need to ensure that the fertilizers that you introduce to the soil are balanced to prevent this from happening in the future.
Higher potassium levels are required during the flowering stage.
Besides turning your cucumber plant’s leaves yellow, lack of potassium will also lower your production.
- Iron Deficiencies
If iron deficiency is the problem, the new leaves will appear yellow while the older ones remain green.
This can be resolved by either targeting the plant or the soil. Liquid iron sprayed on the foliage works fast even though its effects are no lasting.
For the soil, use granular or powdered iron and sprinkle these around the roots.
Whether you choose to spray liquid iron or use the powdered varieties, remember that balance is important when dealing with deficiencies and soil nutrients.
Final Thoughts on Cucumber Leaves Turning Yellow
Having known some of the reasons and causes of your cucumber leaves turning yellow, it is up to you is determine which one is affecting your crop.
Some of these causes are easy to control for instance the water level can be regulated by avoiding over watering the crops or draining the excess water after rains.
Plant pests on the other hand can be controlled by use of the right pesticides.