Bright Spots on Cucumber Leaves: Why They Appear and How to Get Rid of Them

Many gardeners complain that unpleasant spots appear on their precious cucumbers. They can be brown, yellow, or white. Far from always, this is a reason to mentally bury the crop – sometimes it is enough just to adjust the care of it. However, there are situations when spots on cucumber leaves warn of dangerous diseases of the vegetable.

Found yellow spots and holes on cucumber leaves – find out the cause

As experienced gardeners say, there may be several reasons for such a phenomenon. Depending on the complexity of the problem, the methods of combating it differ.

Lack of nutrients

If cucumbers do not have enough vitamins and macronutrients, then you will see that the leaves on the plant begin to turn yellow and desiccate. As a rule, the lower leaves are the first to suffer. Sometimes you can notice the same situation with the veins as well.

How to fight: use a complex mineral fertilizer, making up for the lack of the necessary element.


Plants, like people, suffer from the aggressive rays of the sun, and, if the crop is attacked by the scorching sun, and not enough moisture, you will see a yellow withering spot on the leaf.

How to deal with it: greenhouse plants are most often affected by this problem, so if you notice a burn – tie up the cucumbers so that the leaves do not come into contact with the glass of the greenhouse.


At low temperatures, the fruits on diseased twigs acquire a mottled color, wrinkle, and warp. The first symptoms are the presence of yellow-green spots, and later – the appearance of the mosaic. Then the leaves begin to shrivel and curl.

How to fight: at the first signs of infection, you need to dig up and burn the damaged plants, and if a mosaic appeared in the greenhouse, then dig over the soil there. In order to prevent the situation from repeating, regularly apply fertilizers, treat the garden against pests and disinfect the seeds.

Blackleg and powdery mildew

Blackleg is a fungal disease that affects cucumbers and can lead to the death of the crop. First, the stem turns black, and then there are yellow spots on the leaves.

How to fight it: the first thing to do is to reduce watering, loosen the soil under the plants and sprinkle it with wood ash. Treatment of the soil with a weak solution of manganese solution will not be superfluous either.

Powdery mildew is also considered a dangerous disease, unfortunately, very common to many plants. It is characterized by white or red cloudy spots on the leaves and stems, causing cucumbers to wilt.

How to fight: cut off and burn the damaged leaves, and treat the remaining plants with an antifungal agent. As a prophylactic, carry out fertilization with cowpea infusion, phosphorus, and potassium fertilizers.


The fungal disease, the first symptoms of which can be seen immediately are brown or red round spots up to 5 cm in diameter. Usually, they are pressed into the leaf, and as the disease develops, a hole is formed inside the spot.

How to fight: Planting should be treated with a 1% solution of Bordeaux liquid or 0.4% solution of copper chloride. After two weeks, repeat the spraying and do so periodically for prevention purposes.

False powdery mildew

If you notice such a disease in plants in the initial stages, the first thing you will see is light green spots with veins. Over time, these spots begin to darken and take on a brown hue, and gray fungal spores appear on the back of the leaf.

How to fight: Combine 10 drops of 5% iodine dissolved in 1 liter of milk and mixed with 9 liters of water and spray the solution on cucumbers until the infection disappears completely.

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Written by Emma Miller

I am a registered dietitian nutritionist and own a private nutrition practice, where I provide one-on-one nutritional counseling to patients. I specialize in chronic disease prevention/ management, vegan/ vegetarian nutrition, pre-natal/ postpartum nutrition, wellness coaching, medical nutrition therapy, and weight management.

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