Cucumber Leaves Turning Yellow Can Be an Early Sign of Big Problems

Cucumbers can be such a fun plant to grow, but they don’t come without their issues.

Cucumber leaves turning yellow is one of the more common problems and there are a few different reasons this can happen. This article focuses on the underlying reasons for cucumber leaves turning yellow and how to stop it from happening again.

Reasons Cucumber Leaves Turn Yellow

Cucumber leaves can turn yellow for several different reasons including diseases, root rot, overwatering, and nutrient deficiencies. It’s important to identify the cause in order to take appropriate steps for treatment and prevention.

cucumber leaves turning yellow

When a cucumber plant begins to turn yellow, cucumbers can quickly follow suit, and then the cucumber harvest time will be significantly delayed.  

If your cucumbers have white spots on their leaves then they may have been infected with powdery mildew which will need to be treated with fungicide or organic pest control.

Nutrient Deficiency

If your cucumber plants have a yellow edge on the leaves it could mean that they are lacking certain nutrients, namely nitrogen, iron, or calcium.

Cucumber plants are heavy feeders, needing a lot of nutrients and water.

How to Fix It

You can fix a nutrient issue by fertilizing cucumber plants regularly. You’ll want to make sure you aren’t over-fertilizing, as this could cause further problems for the plant.

This fertilizer has a great 8-4-8 NPK ratio with enough Nitrogen to help with growth and leaf color, but also giving the plant the Phosphorus and Potassium it needs to stay strong.

Farmer's Almanac Fertilizer

Great for feeding cucumbers and nightshade plants like tomatoes.

  • Organic, OMRI Listed
  • 8-4-8 NPK Formula
Check Availability
We earn a commission if you click this link and make a purchase at no additional cost to you.

How to Prevent It

It’s easy to prevent this issue from happening by making sure you are regularly fertilizing your cucumber plant. The fertilizer you use will have instructions for proper use, so make sure you follow that to avoid a future nitrogen deficiency.

Over-Fertilization

Too much of a good thing is also not ideal, as you can cause “nutrient burn” by over-fertilizing your cucumber plants.

Adding too much fertilizer will cause the plant to have trouble taking in water, and since cucumbers are 95% water, this is a problem.

How to Fix it

Stop fertilizing your plants for the time being.

Remove cucumber leaves that have yellowed to allow the plant’s energy to go into healthy, green leaves.

Wait a week or two to see if the problem resolves itself. If it does, check the directions of your fertilizer to make sure you are giving plants the right amounts of the product.

Give the plant about half of the dosage you were previously offering up. Wait and see if the leaves stay green.

How to Prevent it

Get a soil test done to see if your soil has too much of any nutrients. This will help you better analyze which fertilizer to use in the future.

Follow the fertilizer instructions carefully to ensure you are not giving too much to the plant.

Pest Damage

Insects and diseases can be problematic for any plant to grow well, especially cucumbers.

A few common pests of the cucumber could be the cause of yellow leaves.

leafhoppers

Potato Leafhoppers

Potato Leafhoppers can cause cucumber leaves to first turn yellow, then turn brown and wilt.

They feed on the sap within the leaves, causing that part of the leaf to dry out and change color. If left alone, they can destroy the entire plant.

Spider Mites

Spider mites can be really challenging to spot initially. Their webs are translucent, so they can easily pass a quick glance. Eventually, they will start to take over a full leaf and you will definitely start noticing them when the leaf begins to yellow and wilt away.

Cucumber Beetles

If cucumber leaves have small holes on them it can be an indication that the striped cucumber beetle has arrived. Cucumber beetles feed off of cucumber plants leaving large yellow cucumber spots on cucumbers and cucumber leaves.  

If cucumber beetles are allowed to cause enough damage, you will start to see delayed harvest time and yellow cucumbers.

Aphids

Aphids are a nightmare in the garden. They can affect almost any plant, are hard to find, and can be tricky to get rid of. Aphids can also spread disease and other issues from cucumber plant to cucumber plant.

How to Fix it

If there is an infestation of pests on your cucumber plants, there are a few options you can take to get rid of them.

Insecticides, but these can kill beneficial insects.

  • Diatomaceous Earth
  • Neem oil

How to Prevent it

  • Row Covers
  • Companion planting
  • Predator insects – braconid wasps, nematodes

Diseases That Affect Cucumber Plants

Cucumber Mosaic Virus

Cucumber leaves turning yellow can also indicate cucumber plant damage from cucumber mosaic virus or cucumber vein yellowing virus.

These cucumber viruses are spread by aphids who feed off cucumber plants, infect cucumbers and cucumber leaves then move on to infect other cucumber plants. Cucumbers with cucumber vein yellowing will have delayed harvest time again due to cucumbers not being able to reach maturity when cucumber vein yellowing is present in cucumber plants.  

Cucumbers with cucumber mosaic virus will have an overall yellow appearance or spots between veins in cucumbers.  These cucumbers also often develop brown spots on the leaves.

How to Fix it

To get rid of this problem, you’ll need to remove cucumber plants from cucumber beds and destroy them so the cucumber viruses won’t spread to nearby cucumbers. Do NOT add these plants to your compost pile as it could cause issues with next year’s harvest.

If allowed to stay in the garden, aphids and other pests can transfer these to other cucumber or cucurbit plants.

Downy Mildew

If portions of the top of the leaves are turning yellow or showing yellow spots, this could be downy mildew. As these areas expand, the leaves can begin to turn brown as well.

Overwatering

Cucumbers require a large amount of water, but when they get too much water, this can introduce a host of problems.

Whether it’s from too much rain, or human error, overwatering can lead to yellowing leaves.

How to Fix It:

If you suspect that your cucumbers are being over-watered, try giving them less water and see if it makes a difference. Allow the plants to dry out for a day or two before considering watering them again.

How to Prevent It

Check the soil around your plants before watering. If there is water found a few inches down into the soil, then hold off on watering. If that soil is dry, go ahead and water the cucumber plant.

Cucumbers are delicious vegetables that contain lots of vitamin C and potassium. They can provide a lot of yield per season, but don’t come without their problems.

By knowing cucumber plant problems, you can take action in advance and solve cucumbers issues.

Leave a Comment