yellow spots on my cucumber leaves

Leaf Spot Prevention In Cucumbers

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Members of the extensive cucurbit family, cucumbers are a staple in many vegetable gardens. The plants are prolific producers and gardeners have dozens of varieties to choose from when planning their vegetable patch. Because cucurbits are susceptible to a wide variety of diseases and pests, breeders work constantly to develop cultivars with resistance to as many of these problems as possible. No one variety resists all diseases, so gardeners need to do as much as they can to protect their cucumber plants.

Angular Leafspot

Caused by Pseudomonas lachrymans, angular leaf spot causes water-soaked, angular leaf spots that may appear greasy and have yellow halos. The spots do not cross main veins. Initially green, the spots may turn brown and dry up, developing tattered-looking holes in the centers. The disease also infects the stems and fruit of the cucumber plant. To prevent angular leaf spot, plant seeds or seedlings labeled as resistant varieties. Buy only certified disease-free seeds. Don’t use high-nitrogen fertilizer, avoid overhead irrigation and don’t do gardening chores while the cucumber plants are wet. Rotate crops and plant cucumbers away from other cucurbit species. After harvest, plow the cucumber plants under as deeply as you can. Remove all surface plant debris and destroy it away from the garden.

Bacterial Leaf Spot

Leaf spots caused by other bacterial infections can infect the foliage and the fruit, causing the cucumbers to rot on the plant. The spots are very small, distinguishing them from angular leaf spot, and spots are not confined by the veins on the cucumber plant’s leaves. Bacterial leaf spots cause lesions on the cucumber which can penetrate the cucumber rind into the flesh of the fruit. Plant resistant varieties and practice prevention as for angular leaf spot disease.

Cucumber Mosaic Virus

Yellow spots and streaks on cucumber leaves, yellow leaf veins, ring spots or patterns of different shades of green are all symptoms of cucumber mosaic virus. This disease can be spread by insects such as aphids, via weeds and by failure to disinfect gardening tools and your hands after contact with an infected plant. Cucumber mosaic virus cannot be diagnosed from symptoms alone. Since there are no chemical treatments or preventives for cucumber mosaic virus, remove infected plants and destroy them away from the garden. Grow cucumbers from seed rather than seedlings. Keep the garden weed-free and disinfect gardening tools between cuts and between plants to avoid spreading the disease. Wash hands thoroughly after handling an infected cucumber plant. If you wear gloves while gardening, change or wash the gloves before handling healthy plants.

Fungal Leaf Spots

Myriad fungal infections can attack cucumber plants, including alternaria, anthracnose, downy and powdery mildews, gunny stem blight and phytophthora, septoria and ulocladium. Most produce tan or brown spots, sometimes with yellow halos. The spots often appear sunken or wet, and the centers may fall out, leaving the cucumber plant’s foliage looking ragged. Downy and powdery mildew produce white spots. These leaf spot infections may spread to the stems and the fruit of the cucumber plant, limiting or ruining the harvest. Proper diagnosis of the infection is crucial to treating or preventing it. Many cooperative extension service offices and university horticulture departments can diagnose leaf infections, sometimes for free. To prevent fungal infections, plant resistant cucumber varieties, if available. Rotate crops in the vegetable garden each year. Make sure the cucumber plants have good air circulation and are not crowded together. Remove severely infected plants and destroy them away from the garden. Avoid overhead watering. If the infection is light, you may be able to prune away the diseased area and prevent the infection from spreading. Always disinfect pruning tools between pruning cuts and in between each plant.

Leaf Spot Prevention In Cucumbers. Members of the extensive cucurbit family, cucumbers are a staple in many vegetable gardens. The plants are prolific producers and gardeners have dozens of varieties to choose from when planning their vegetable patch. Because cucurbits are susceptible to a wide variety of diseases and …

Why Are My Cucumber Leaves Turning Yellow And Dying?

Cucumber leaves turning yellow usually means one thing:

A sickly plant in need of attention.

In this guide, I’ll show you how to identify the cause and what you can do about it.

What Is Happening?

The loss of the green coloration of the leaves, caused by a lack of chlorophyll, is known as chlorosis.

As chlorophyll is essential for converting sunlight into chemical energy, its reduction threatens the health of your cucumber plant.

But to find out exactly what’s causing it you need to take a closer look.

Cucumber Leaves Turning Yellow: The Causes

The causes of chlorosis usually fall into one of 5 categories: plant pests, diseases, nutritional deficiencies, light problems, and water problems.

Let’s take a closer look at how you can identify your problem, and importantly, what you can do about it:

Plant Pests

Aphids (Aphidoidea) on a leaf

You’ve probably come across a variety of different insects on your plants. But did you know that some of them suck the sap out of the leaves?

This is a common cause of leaf discoloration and can cause them to turn yellow.

These are some of the most common:

Aphids – these small oval-shaped insects hang out on the underside of leaves. They are often green or yellow and leave behind a sticky black substance called honeydew.

Spider Mites – suck on the cucumber leaves causing yellow stippling. They are another insect that’s usually found on leaf undersides where they leave behind a silvery, fine webbing.

Whiteflies – if you shake the leaves and see a cloud of tiny, white winged insects rise up, then your plant is infested with whiteflies. Like aphids, they also leave behind honeydew.

You can spray insecticidal soap on the leaves of the plant to get rid of these unwanted bugs.

The Potato Leafhopper

Potato Leafhopper (Empoasca fabae) Source: gailhampshire

These are bigger than the pests mentioned above, but they also enjoy feeding on your plants by sucking the sap from the leaves.

While feeding, they inject a toxin that causes yellowing. And as the damage accumulates, the leaves will eventually fall from the plant.

You can use insecticides to kill potato leafhoppers. But for obvious reasons, that’s not always desirable on plants that you’re using for food.

So another method is to keep the area free from weeds and use row covers over the plants to keep the insects away.

Plant Diseases

Cucumber mosaic virus

Diseases are often responsible for the appearance of yellow spots or streaks on cucumber leaves.

Check to see if your plants are infected with any of these:

Cucumber Mosaic Virus

Are the leaves wrinkled and downward-curving with yellow spots?

Then they might be infected by cucumber mosaic virus.

Unfortunately, the only solution to this problem is to remove the infected plants because there’s no treatment available. If left, the disease will often spread as it’s carried by aphids and leafhoppers.

Be aware that it can live in the soil and infect new plants the following year.

The same also applies to our next disease…

Fusarium Wilt

Take a close look at the older leaves. Are they turning yellow, starting from the edges and spreading inwards?

Cucumber beetle larvae are responsible for its spread as they feed on the plant’s roots.

The same as mosaic virus, the only way to deal with it is to get rid of the infected plants. There are a number of options for cultural and biological control of this fungus.

Another similar fungus is Verticillium wilt. This is common if your cucumber plants are planted in an area that was previously used for vegetables such as peppers, tomatoes, potatoes, or eggplants.

Downy Mildew

The telltale signs of downy mildew are yellow spots on the upper surface of the leaves which turn to brown later on.

These spots are angularly bounded by veins in the leaves, giving an almost patchwork appearance.

And in high humidity, a grey fuzz can be found on the underside of the leaves.

To prevent and manage the disease there are several options:

  • Planting cucumber varieties that have a high level of resistance.
  • Improve air circulation around the cucumber plants and keep leaves dry by using wide row spacing and drip irrigation.
  • Remove infected plants immediately to prevent spread.
  • Contact and systemic fungicides are available that are effective against downy mildew when applied early in the disease progression.

Nutritional Deficiency

Cucumbers need a number of different nutrients to grow properly, and if these are lacking chlorosis can occur.

To accurately assess whether your plant is lacking in specific nutrients it’s a good idea to have the soil in your vegetable garden tested.

The following are the most common deficiencies that can result in your cucumber plant leaves turning yellow:

Nitrogen Deficiency

Not only will nitrogen deficiency turn cuke leaves yellow, but it also stunts their growth. With the plant eventually dying if the situation is severe.

Look out for the older leaves on the plant turning yellow along central veins and at the tips. With newer leaves continuing to look green.

Fortunately, this problem is also very easy to fix. You can increase the nitrogen content of the soil by adding a 2-inch layer of compost.

Or, you can add 1-2 tablespoons of 6-10-10 fertilizer if you start to notice a problem.

Another thing you can do is use a tablespoon of ammonium nitrate when you see the flowers of the plant start to bloom. Add it to the soil again 3 weeks later.

But, be careful not to put too much fertilizer in the soil as it will prevent the plant from producing its fruit, the cucumbers themselves!

Iron Deficiency

If new leaves are yellow with green veins, but the older leaves are still green, then iron deficiency is a possible cause.

To treat this deficiency you can add granular or powdered chelated iron to the soil around the root zone. Or you can spray liquid iron on the plant.

Potassium Deficiency

Cucumbers have a high potassium requirement, and are one of the only crops that need more potassium than nitrogen

The symptoms of potassium deficiency are leaves that turn yellow at their tips and edges. Young leaves tend to be small and dull looking, and are cupped or puckered. The cucumber fruit often have a club-shaped appearance due to being narrow close to the stem.

Using a well-balanced fertilizer can solve this cucumber plant problem. And treat the soil for acidity or alkalinity if needed.

Zinc Deficiency

To identify cucumber plants suffering from a zinc deficiency, look for older leaves turning yellow between the vein. Leaf size is usually small and growth of the plant is restricted.

Spraying with a zinc sulfate solution is an easy way to correct this problem. You can also use organic kelp.

Water Related Yellowing

Be careful not to overwater your cukes. Overwatering can lead to oxygen-deprived roots, a sign of which is the leaves turning yellow and wilting. Including rainfall, cucumber plants only need about 1-2 inches of water each week.

If your soil has drainage problems, consider loosening it with sand. Another solution is to grow your cukes in raised beds instead. Or containers with large drainage holes.

Lack Of Sunlight

Sometimes, the reason for yellow droopy leaves on your cucumber plant is simply that it’s not getting enough sunlight. Try moving them to a location in your garden where they can get at least 6 hours per day.

3 thoughts on “Why Are My Cucumber Leaves Turning Yellow And Dying?”

Six out of my nine cucumber plants have wilted with leaves gone yellow. I have been watering them daily with a little water and on one occasion I added tomato fertiliser liquid to the water. I have stopped watering for the last four days but none of the plants have recovered. The three that are OK seem to be thriving yet received the same treatment. The plants are in the greenhouse which has been extremely hot the last few days. I know now that I have over watered the plants but has the tomato fertiliser and hot greenhouse conditions had and impact as well.

Are your cucumber leaves turning yellow? In this guide, we help you to identify the main cause of your problem and tell you what you can do about it.