How to Combat Cucumber Diseases

Last update: May 4, 2021

Cucumbers are susceptible to different diseases: mostly fungal and viral infections. A few of the most common cucumber diseases include powdery mildew, bacterial wilt, cucumber beetles, cucumber mosaic, and downy mildew.

Fortunately, lots of these diseases can be treated. Take a peek at the article below to learn how to keep your cucumbers happy, healthy and tasty.

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What Are Some Common Cucumber Diseases?

1. Powdery Mildew

It is one of the most common diseases in cucumbers. Powdery mildew shows signs of white powdery substance encompassing the whole leaves of the plant. Usually, it begins in little spots then scatters throughout the leaves.

This fungal disease may cause poor growth of the fruits specifically if the infection is severe. The leaves of the cucumber begin to wither and then fall off prematurely. Overhead watering and poor air circulation can contribute to such problem.

At the first sign of the disease, the use of fungicidal sprays can help. In order to avoid wetting leaves, use underground or surface watering method.

To keep the infection at bay, plant cucumbers in full sun. If your plants are already infected with powdery mildew, spraying with neem oil can prevent the disease from spreading. Just remember not to spray in the heat of the day.

Here’s a great video explaining how to treat powdery mildew.​

2. Bacterial Wilt

Bacterial wilt can cause the plants to wilt and then die fast. You will know if the disease is present in the plant when a white substance will stick to your finger the moment you pull it away.

The bacteria that are causing the disease invade the plant’s vascular tissues, which leads to a rapid wilt of the plant. The sticky substance produced by the bacterial wilt organism plugs the tissues, preventing the transport of water.

As the disease progresses, it begins with a single leaf then the entire plant. In order to control the infection, destroy any affected plants. It is also best to implement the right insecticide program to control bacterial wilt and prevent it from occurring.

Here’s an awesome video explaining how to spot bacterial wilt.​

3. Cucumber Beetles

Cucumber beetles are known for their black and yellow stripes, while some of them are spotted. These insects chew small holes in the fruit’s flowers or leaves.

They usually carry wilt disease and love to suck on young seedlings. Aside from this, the larvae of these pesky insects feed on the roots. One thing you can do with cucumber beetles is pick them by hand. They move slow during the morning or evening.

To kill them, prepare a cup of soapy water and drop them. On the other hand, keep the bugs at bay by applying pesticides. Once the seedlings blossom, stop spraying for cucumber beetles to allow bees to start pollinating the plants.

Here’s what a striped cucumber beetle looks like:​

Cucumber beetle damage

4. Cucumber Mosaic

This type of cucumber disease affects the flower, leaf, stem and growth of the plant. When the infection strikes, it may lead to the formation of prominent foliar yellow mosaic, severe plant stunting, malformation, reduction of leaf size, downward leaf curling and more.

The flowers may show signs of prominent abnormalities. This disease is very common. The virus is transmitted from one plant to another by various kinds of aphids.

Good thing, mosaic disease can be managed by controlling the presence of cucumber beetles and aphids throughout the season. It is best to use good quality seed all the time. Control perennial weeds to prevent the disease from occurring. On the other hand, you may also use insecticides and mineral oils.

Here’s a great paper on Cucumber Mosaic Virus from the University of Hawaii at Manoa.​

cucumber mosaic

5. Downy Mildew

A cucumber plant has downy mildew when it shows signs of angular yellow spots on its leaves. This fungal disease can be treated and prevented in different ways.

If your plant is already infected with the disease, pull it to prevent the infection from spreading. Use good cultural practices to avoid the infection from occurring and use fungicides to stop the disease.

Check out this video from the Rustic Garden to learn more about spotting and treating downy mildew.​

Are Deformed Or Misshapen Cucumbers Infected With A Disease?

Some people think that misshapen or deformed cucumbers are diseased. However, when a cucumber is funny shaped, it does not mean it is infected with a disease. There are possible reasons deformed cucumbers occur.

One possible reason is poor pollination. If there is low insect activity in your garden, it may lead to misshapen cucumbers.

Plants need honeybees for pollination and this process should not be interrupted. Other reasons for funny shaped fruits are high temperature, insufficient water and too much fertilizer.

Here’s an awesome video from Man Living Naturally if you’re really having trouble with deformed cucumbers:​

Why Do Cucumbers Turn White?

Nowadays, there are cucumber seeds that are bred to produce white fruit. However, if you have planted green cucumber varieties but you get white cucumbers, one possible reason is powdery mildew.

When it spreads, the whole fruit may be covered with the mold. However, when a cucumber appears white it does not necessarily mean it is infected with a disease.

There are another two possible reasons cucumbers turn white. The first one is blanching, which occurs when the fruit is entirely covered by leaves.

Keep in mind that cucumbers are in need of sunlight to develop and be able to maintain its green color. To prevent blanching, make sure to position the fruit appropriately so that it receives the right amount of sunlight it needs.

It is advisable to snip out a large leaf or two to expose the fruit. On the other hand, excessive moisture may also cause cucumbers to turn pale or white. Water tends to leach nutrients from the soil.

The absence or lack of nutrients changes the color of the fruit into white. To address the problem, water only when necessary and use a fertilizer rich in phosphorus. It is best to keep in mind that diseased white cucumbers are not safe to eat. However, those cucumbers that turned pale or white due to blanching or too much moisture can be eaten.

There are different varieties of cucumber. Most cucumbers diseases are fungal infections. The good news is, you can avoid these problems by selecting and planting cucumber varieties that are disease-resistant. On the other hand, you need to act fast and find a solution at the first sign of infection. When using insecticide, always wear protective clothing and gloves.

Photo Credits

Photo by Scott Nelson licensed under CC BY 2.0.

Photo by Rob Mitchell licensed under GNU 1.3..

Photo by Scot Nelson licensed under CC BY 2.0.

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