Cucumber Leaves Turning Yellow – What Is It?

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My pickling cucumbers are flowering and getting pollinated like mad! It’s truly amazing. Except for the cucumber leaves turning yellow, which I can’t discern for the life of me. Why is this happening?

I am loving my garden this year and don’t want to sacrifice any of those adorable and delicious pickling cucumbers. I’m hot on the case of trying to diagnose the yellow spots on cucumber leaves in my pickle garden.

I’m going to chronicle my journey here and share any tips and tricks I decide to try. I’ll also share my suspicions as to why this is happening. Hopefully it’s reversible!

Why Are My Cucumber Leaves Turning Yellow?

Figuring out the cause of the yellow spots on our pickling cucumber leaves may take some time. I’m going to list out my theories for why our pickling cucumber leaves have yellow spots.

• Is it overwatering? Leaves can turn yellow when they get too much water. We’ve had a sprinkler hooked up on a daily irrigation schedule for at least two or three weeks now. We’ve also left it go even if we got rain. Perhaps it’s too much water? But again, the regular cucumbers are doing just fine. The easy fix would be turning off my watering system or repositioning it and watering manually for a few days.
• Is it low nitrogen? Another gardener advised me that low nitrogen can cause yellow spots on cucumber leaves. An easy fix for this would be applying some bloodmeal, which adds nitrogen to the soil. We actually should have some because I’ve used bloodmeal to deter squirrels from the garden in previous years.
• Is it cucumber mosaic virus? It sure looks like it! I am afraid of this being the case, because I hate destroying any of my plants for any reason. Especially when the plants are producing fruits and veggies. I am going to keep researching this and make a judgement call. If it is cucumber mosaic virus, I should probably handle it before the virus spreads to other plants. (gulp!)
• Could it be cucumber beetles?! I’ve just heard from another gardener who had these same markings on her cucumber leaves. As it turns out, she was dealing with a cucumber beetle infestation. This gardener said unfortunately she lost all of her cucumber plants to the cucumber beetles. I’ll definitely be doing more research on this garden pest!

Cucumber Leaves Turning Yellow – What Gives!?

It’s so frustrating not to know what’s causing yellow cucumber leaves. The leaves aren’t fully yellow but have green and yellow splotches. This seems to support the theory of cucumber mosaic virus – my least favorite choice of the game, what’s wrong with my cucumbers.

Our cucumbers are growing so vigorously that I didn’t expect a problem like this. They’ve largely escaped the damage by the awful Japanese beetle infestation.

Our pickling cucumbers aren’t currently showing signs of issues with squash bugs and vine borers.

I guess they were just doing too well to skate past all that unscathed! So now we go to battle with… whatever this is.

What If It *IS* Cucumber Mosaic Virus?

It seems it would be wise to have a plan in mind in case our yellow cucumber leaves turn out to be a result of the cucumber mosaic virus. Right now, that looks like the most likely situation based on photographic comparisons.

If it is cucumber mosaic virus, we may have no choice but to remove and destroy or safely discard the infected cucumber plants. If it spreads easily from contaminated tools, gloves, hands, and aphids, it seems like too great a risk even considering they’re productive plants.

The GOOD news is I just planted new cucumber plants the other day on July 7! I saw a few of our regular cucumbers wilting, which I believed to be a sign of vine borer infestation. Planting a new batch of cucumbers made for a quick backup plan.

(If you’re interested, be sure to check out our list of what to plant in July for your succession planting and fall harvest needs!)

Why Are Cucumber Plants Turning Yellow? | Questions to Help

When your cucumber leaves turn yellow, it’s time to do a little detective work. Consider these questions carefully to help lead you to your next steps:

• Did you see aphids on your plants earlier in the season?
• Is the soil constantly damp? Do you see mushrooms or other fungi growing?
• Could it be a nutrient deficiency in the soil, such as low nitrogen?

Watering – If it is a watering problem, that’s an easy fix. Adjust your irrigation system or water less often.

Fertilizer – Perhaps it’s a fertilizer issue—a nutrient deficiency. If feeding is the problem, consider adding some bloodmeal to the soil around your plants. This will increase nitrogen levels naturally.

Cucumber Mosaic Virus – If it is the cucumber mosaic virus, we are so sorry for your loss. Just about all sources we’ve researched so far strongly urge removal and destruction of the plant. Some even say not to compost it but to put it out with the trash. And, some sources even say the seeds may be contaminated and to be sure not to save those ones.

If you find your cucumber leaves turning yellow and think it is the mosaic virus, it may be best to just listen to the experts and remove the plants.

It pains me to think of doing this but it will be sacrificing one or two plants to save the whole garden.

(And I think I read that rose bushes can get it, too!)

Cucumber Beetles – Of course, there’s also the chance that the problem is an infestation of cucumber beetles. As it turns out, cucumber beetles can kill your plants – I never knew this and just thought they were a pain in the butt! Plants may not survive when the cucumber beetles infect them with bacterial wilt or when cucumber beetle larvae chew up the roots.

As with most things, a pound of prevention is worth a ton of cure. However, I’ve heard from a local gardener that pruning away the bad leaves and treating the plant with Neem oil and the soil with food grade diatomaceous earth can help.

Final Thoughts: Yellow Spots on Cucumber Leaves

Discovering my pickling cucumber plants with leaves resembling yellow and green tie-dye gave me a clue that something’s wrong.

I’ve been so busy on pest patrol in the garden that I haven’t even given much thought to the quality and condition of the leaves. Unless I’m scraping off bug eggs, of course.

But looking at these plants, I do see some buggy holes. This seems to indicate pest damage!

With pickling cucumber leaves turning yellow, I realize the situation may be dire or if I’m lucky, it could be something we can solve.

I wanted to put together a post to help other gardeners finding themselves with yellow cucumber leaves.

(Hopefully yours is just a watering issue or a feeding schedule that you can amend!)

If it’s the cucumber beetles or the mosaic virus leaving cucumber leaves yellow in its wake, we’ll get through it together. Time will tell.

I’d love to hear from you if you’re going through anything with yellow spots on cucumber leaves, mosaic virus, cucumber beetle infestation, or similar. Let’s chat in the comments and help each other with tips!

Happy Gardening and good luck!