Yellow leaves on cucumber plant: causes & solutions

Yellow leaves on your cucumber plant are a sign of care errors, diseases or a pest infestation. Once you know the various causes, you can counteract the problem with the appropriate solutions.

Wrong watered

If you spot yellow leaves on your cucumber plant, you should always check the substrate at the site first. One of the most common causes of leaf yellowing on Cucumis sativus is incorrect water supply. While overwatering rarely leads to yellow leaves, these are a direct indication of a lack of water. Check the substrate for dryness with your thumb. If it is too dry, you will have to water it to re-supply the cucumber plant with moisture. Use only water with little lime for this:

• Rainwater
• Filter water
• stale water

The plants are watered daily in the morning so that too much moisture does not evaporate. If the site is constantly struggling with drought, mulch. The mulch layer protects the soil from drying out.

Note: Be careful not to pour the water over the leaves as this can also cause yellowing. Only water the substrate.

Missing nutrients

Cucumbers are among the high eaters and must therefore be supplied with sufficient nutrients. If they lack food, this is indicated by yellowing of the foliage and poor vitality of the plant. Ideal fertilizers for cucumbers are organic slow-release fertilizers that are incorporated when planting. Are suitable:

• well-ripened compost
• rotted horse or cattle manure

Powdery mildew

Yellow leaves on your cucumber plant are often caused by fungal infections, especially powdery mildew (Erysiphaceae). This is caused by spores that get onto the cucumbers through spray water, wind or damp fallen leaves and spread there. Powdery mildew can be recognized by the following symptoms:

• white coating on leaf surface
• powdery
• yellow discoloration occurs
• Leaves dry up
• Leaves roll up

In the worst case, the entire cucumber plant can die. Powdery mildew should not be underestimated, especially in warm weather. For this reason, you have to use your own sprays and use them to wipe off the mildew. The following mixtures are suitable:

• 1 part milk and 2 parts water
• Water and a few drops of washing-up liquid
• 1 part baking powder and 10 parts water

Mix one of these agents and apply it at regular intervals. As an alternative to these, you can make a brew from field horsetail or nettles and use this diluted.

Tip: Downy mildew (Peronosporales) also occurs in cucumbers and appears on the underside of the leaves with a white-grayish to brown fungus coating and yellowed, blotchy leaves. You can use the same solutions as powdery mildew to combat the wrong ones, which are more common in damp weather.

Cucumber mosaic virus

The cucumber mosaic virus (cucumovirus) causes leaf discoloration, which, according to the name, resembles a mosaic. The leaves are strewn with yellow spots and wither until you fight the virus. If the infestation is advanced, warts form on the skin of the fruit and they no longer ripen properly. Since the virus is transmitted by aphids, you need to remove them, as well as the yellowed leaves and infected fruits of the cucumber plant. As with other diseases, you should never compost the parts of the plant, as this could allow viruses and fungi to spread again in the garden. The residual waste is better suited for disposal.

Note: The leaf spot disease can be combated in the same way as the cucumber mosaic virus, but can be recognized by different symptoms. Individual leaves turn yellow locally, then brownish and finally they die.

Verticillium wilt

Verticillium wilt, which is caused by the fungi of the same name, is one of the most dangerous fungal diseases of the cucumber plant. Unfortunately, there is nothing you can do about Verticillium wilt, as the fungi can spread too quickly and destroy your entire culture. For this reason, you must sort out and dispose of infected specimens. If fruits have still formed on these plants, you must also dispose of them, as they are inedible. If your plants are wilting, you can tell by the following symptoms:

• Leaves turn light green
• lower leaves affected at the beginning
• Leaves turn yellow strongly
• Infestation spreads to the entire plant
• Leaves wither
• die off
• Plant weakens to the point of death

The symptoms are more pronounced in the heat. The fungi are introduced either through contaminated tools or plants.

Tip: Do not use the location of infected specimens for susceptible crops for a period of ten years. The Verticillium fungi can remain in the soil for this period of time.

Aphids

As described above, aphids are the cause of the cucumber mosaic virus. The pests are not infrequently found in large settlements on the cucumber plants and can cause yellow leaves even without the transmission of the cucumber mosaic virus. Aphids can suddenly appear on your Cucumis sativus plants, making them a dangerous nuisance. In contrast to other pests, care errors are not only the reason for a settlement. Symptoms of an aphid infestation are:

• Aphids can be seen on the cucumber plant
• Stunted foliage
• yellow leaves
• Honeydew recognizable

Since Aphidoidea often attract ants, you have to expect these as well. Fortunately, there are plenty of home remedies you can use to fight the lice. If you do not want to use beneficial insects such as lacewings, ladybirds or gall mosquitoes, you are still left with pesticides on the following basis:

• milk
• Neem oil

While you can spray the neem oil directly on the lice, you need to mix the milk in a 1: 2 ratio with low-lime water. Treat your cucumber plants with the sprays until the aphids are no longer present. Remove infected shoots and leaves.

Spider mites

Spider mites are also common cucumber pests whose damage pattern is similar to that of aphids. The most noticeable symptom are the webs, which are reminiscent of cobwebs and appear between the leaves and shoot axes. The causes for an infestation with the Tetranychidae are varied:

• low humidity
• planted too closely
• Lack of water

Cucumber plants in the greenhouse in particular have to struggle with the annoying insects. Effective solutions include spraying neem oil, using a sharp jet of water, and removing the infected leaves and shoots. You can prevent spider mites by not letting the plants dry out. That would encourage further infestation.

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