5 Reasons of Yellow Spots on Cucumber Leaves [Solution]

Cucumber is very popular among gardeners. Because it is highly nutritious and very easy to grow as well.

But cucumbers do need the care to prevent some fungal, viral, and bacterial diseases that cause yellow leaf spots.

Downy mildew, Angular leaf spot, Cucumber Mosaic Virus, Anthracnose, and Scab are the reasons for yellow spots on the cucumber leaves. 

Identifying the actual reason is very crucial because improper treatment can be harmful to the garden. 

In this article, I’ve added all the possible reasons with the identifications and solutions that will help you get rid of the yellow spots on your cucumber plants.

So, let’s begin-

 How to Get Rid of Yellow Spots on Cucumber Leaves

How to Get Rid of Yellow Spots on Cucumber Leaves

1. Downy Mildew of Cucumber

Downy Mildew is caused by Pseudoperonospora cubensis which is considered to be a fungus. But it’s actually a kind of mold. Anyway, it’s a very serious disease, especially for the cucurbits family including cucumber, squashes, pumpkins, etc. 

And the disease reduces cucumber production drastically up to 40% if it is not treated in time. So the growers always have to look out for the symptoms.

It causes large, yellow, angular spots on the upper side of the cucumber leaves. And purplish and brown spots on the lower side of the leaves. Eventually, the leaves start drying and fall off.

Downy mildew prefers the temperature range of 20-30° C for rapid infection. It spreads very fast in wet and humid conditions.

Control Measure 

The first step of treatment is to remove all the cucumber leaves that have yellow spots on them. After that, apply a fungicide. 

Since cucumbers are very tender plants, we have to select a fungicide that is not toxic to the environment but effective against powdery mildew. You can pick this fungicide (our pick: Bonide Copper Fungicide)

Also, I’ve added some home-made recipes that you can try for downy mildew-

#Recipe 1:- Baking Soda Spray Recipe

Mix 3 teaspoons of baking soda and 1 teaspoon of liquid soap in 4 liters of water. Mix well and spray on the cucumber leaves thoroughly.

#Recipe 2:- Copper Spray Recipe

Mix 5 teaspoons of copper sulfate and 75 ml of Hydrated lime in 2 liters of water. Mix this solution very well every time before spraying. Wash the sprayer thoroughly after every use because this solution is very corrosive.

#Recipe 3:- Epsom Salt Spray Recipe 

Mix 3 teaspoons of Epsom salt in 2 liters of water. You can spray this solution every week.

Preventive Measure

You can try many resistant varieties that are available in the market. Downy mildew spreads very fast through water movement. So water the plants from the base and avoid wetting the leaves. Clear off the weeds and keep proper planting space for better airflow.

2. Angular Leaf Spots

Angular leaf spot is a very common bacterial disease of cucumbers.

This appears as water-soaked and small yellow dots on cucumber leaves. It’s called angular leaf spot because the spot expands to the veins and gives an angular shape.

Sometimes it exudes milky sap in humid conditions. Eventually, they turn brown and dry up making holes in the center of the spots. Tiny spots can also be seen on fruits and these spots on the cucumber can even initiate fruit rot.

Control Measure

You can try bactericides to reduce the severity of the infection. You can also try the copper spray on a regular basis. (our pick: Bonide Copper Fungicide)

Preventive Measure

It’s a seed-borne disease. So it’s best to sow resistant variety seeds which are available in the market. Grow cucumbers on a trellis or vertical wires to increase air circulation around them. Growing over a framework also helps to identify the symptoms earlier. 

Get rid of the infected cucumber leaves because this disease can survive upto 2 years in debris if left untreated. Do not grow cucumbers in the same place year after year. Change the place every two years. 

Keep the leaves dry as much as possible. After harvesting, remove all the plants and plow the soil as deep as possible.

3. Cucumber Mosaic Virus

This is a viral disease for cucumbers. It appears as little and bright yellow spots in a mosaic-like pattern or ring-like pattern in the leaves. Sometimes the vein also turns yellow and leaves start curling downward. 

Plants become stunted. This is a very serious disease because it makes the cucumbers distorted and discolored. It’s usually transmitted by aphids, garden tools, or human contact.  

Control Measure

Sadly there is no control measure available for the mosaic virus.

Get rid of the aphids as soon as you notice their presence because they can be the carrier of the cucumber mosaic virus. You can pick a powerful insecticide(Our pick: Monterey Garden Insect Spray).

Or You can try some home remedies below for aphid control to prevent your cucumbers from the virus.

#Recipe 4:- Insecticidal Soap Recipe

Mix 5 teaspoons of liquid soap and 2 teaspoons of oil in 1 liter of water. spray this solution twice a week. This will help repel the aphids. 

#Recipe 5:- Garlic Spray

Take 5 garlic cloves in 250 ml of water and mix them in a blender. Then add water to make it a one-liter solution and put it into the sprayer. You can spray it every week on both sides of the leaf.

Preventive Measure

Always use virus-free seeds for cucumbers. Keep the garden weed-free. If you notice aphids apply insecticidal soap and garlic spray

4. Anthracnose

It’s a fungal disease of cucurbits. It mostly attacks melons, watermelons, and cucumbers. This disease usually starts in the mid-summer. Because humid and wet climatic conditions help in its infection.

It produces a mixture of yellow and brown spots on the cucumber leaves. Later the center of the spot dries and falls out. It also damages stems and fruits and causes dark spots on the cucumbers. 

This fungus is seed-borne and survives on plant residues. 

Control Measure 

You need to pick the best fungicide for your plant that will not hamper your cucumber production. There are many fungicides for the control of anthracnose but only some of them are nature-friendly and safe.(our pick: Bonide Copper Fungicide)

Preventive measure

Before buying seeds make sure they are resistant varieties. Allow a lot of space between the plants to keep the airflow and weed regularly.

5. Scab

It is another fungal problem Of cucumber that causes irregular-shaped, grayish spots with yellow halos on the leaves. Leaf spots are usually small, pale-yellow. 

Eventually, the leaves start drying and fall out. If uncontrolled, the problem can cause the plant to die. This disease usually occurs in mid-summer.

It’s very important to take the necessary steps because it makes the Cucumber small and oozing and sometimes inedible. 

Control Measure

Choose a good fungicide(our pick: Bonide Copper Fungicide) that doesn’t injure your cucumber. You can try seed treatment with proper chemicals according to the label direction.

#Note:- You can apply the homemade remedies that are mentioned above in the downy mildew section for any fungal problems like Anthracnose and Scab

Preventive Measure

Always use healthy seeds from certified growers.

Water the plants at the base, keeping the foliage dry. Clear away plant debris regularly because moist and rotting debris harbor these fungal organisms.


I have tried to provide all the necessary information about the yellow spots and I hope you have got your solution among them.

These spots sometimes can be tricky to get rid of.

But don’t worry! At the first sign of any symptoms start taking proper actions and always take preventive measures. That’ll be all.

Don’t forget to share your experience in the comments below about how you treat the yellow spots on your plants and let me know if you have any queries.

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