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Why Do My Cucumbers Have Black Specks

Plants are very good at showing symptoms when something wrong is going on with them. In some cases, diseases are treatable, but other times, unfortunately, there isn’t anything we can do to stop a plant disease from taking over. Cucumbers will show symptoms like wilting leaves, yellowing leaves, deformed fruit, drying up, and sometimes black specks will appear.

Black specks can mean a few different things when it comes to cucumbers. Either they have a disease, or there is a pest attacking your cucumber plant. Sometimes, the black specks are bugs themselves. 

To find out what diseases and pests cause these black specks and how to deal with them, continue reading.

What Causes Black Specks on Cucumbers?

As we know, two main things that cause black specks—those being diseases or pests. But precisely what diseases and pests are we dealing with? Let’s find out.

Four Lined Plant Bug- Up close this bug looks like a small
beetle like bug with yellow and black stripes. These bugs will leave tiny holes in your plants leaves where they are eating your plant. An extreme case will leave your plant looking wilted and leaves browning. 
Anthracnose-Caused by warm moist weather, anthracnose is a fungal disease. It starts by leaving dead, spots along the leaves. Once greatly effected, the leaves will begin to fall off. It will do the same to cucumbers that have already begun to grow. 
Aphids- Gathering in small clusters around your plants, aphids like to feed on the new growth of your cucumber plant. Typically, aphids don’t do a whole lot of damage to cucumbers, but they do transmit nasty diseases like the mosaic disease that you don’t want in your garden. Blight- Specifically gummy stem blight will leave black looking smudges or spots on cucumbers. Blight is also a fungal disease. When effected, cucumber plants stems will begin to look spotted and rotten. They may even begin oozing a brownish substance. 
Squash Bugs- Squash bugs work quickly in eating much of a cucumber plant, leaving it looking brown and yellow. They target the sap in the leaves, starting with small holes in the leaves and eventually taking over the whole plant. Bacterial Leaf Spots- Starting as yellowing around the edges of leaves, it can quickly turn into browning spots and eventually black spots on the whole leaf. The leaves will eventually fall off. This the most common bacterial disease that effects peppers, but also will attack melons, cucumbers and squashes. 

Cures For the Diseases

Unfortunately, for all three diseases listed, there are no total cures. Each of the diseases is manageable but will stick around for the season. Here is how you can treat and manage these diseases.


  • Because anthracnose is a fungal disease, it lives in the soil and will return year after year if you continue to plant in that affected soil. So this can be tricky to deal with. The recommended approach is to rip out and burn any affected plants. Do not put them in your compost because otherwise, you are tainting that compost.
  • Afterward, you can cover your soil with h2O2 and let the sun try and burn out all those bad funguses. Next year and for the years after, rotate your crops. If there is bad rainy weather, you can put down fungicides; however, too much fungicide can harm good things we want in our soil, like earthworms.

Gummy Stem Blight 

  • Gummy stem blight is a fungal disease, so to try and fix the problem, you would go about it the same way you went about anthracnose. Burn your crops, rotate your crops, and burn your soil. The silver lining to gummy stem blight is that it’s very manageable with fungicides up until harvest time. So you may still be able to get a decent yield out of your plants. 

Bacterial Leaf Spots

  • Bacterial leaf spots usually happen because a bug or seed-borne carries it over. So the best thing to do is to be proactive against this bacterial disease. Hot water treats your seeds and makes sure you stay on top of getting rid of those bugs.
  • These bacteria also grow in moist conditions, so having a dry environment is essential. Try drip irrigation or hand watering instead of using an overhead water sprinkler. If you get the disease, you can try just removing the leaves as they get worse. Copper-based sprays may also help you curb the problem. 

Cures For the Pests

Getting rid of pests is generally the same, but with slight differences. Some bugs do more damage than others, while some are a bit tamer. But the good thing is that you can usually get rid of bugs fairly easily. 

Four Lined Leaf Bugs

  • Four-lined leaf bugs are some of the easier ones. They will only stick around for about a month and usually stick to eating the leaves. Most gardeners tend to leave these bugs alone, so their damage is minimal, but putting down neem oil, Dr. Bronners, or liquid dish soap/oil combination works effectively. 


  • Aphids can do a lot of damage, but only if you let them. They are traveler bugs and will go from plant to plant-eating away at it. If you don’t want them on some plants, you can spray them with water or brush them off. The liquid dish soap/oil combination applied twice a week to your plants works great at keeping them away. You can also try the vinegar method. One parts vinegar and 3 parts water in a spray bottle and spray your plants. 

Squash Bugs

  • Squash bugs are also fairly easy to get rid of. If you can find their eggs, brush them off into a bowl of soapy water (to kill them). And again, using the liquid dish soap/oil method works for these bugs. 

Are Cucumbers With Black Specks Edible?

Luckily when it comes to all these diseases mentioned and the pests mentioned, causing or looking like black specks, the cucumbers on the plant are still edible. However, if the damage is so severe, you may not want to eat the cucumbers.

You will have to take a thorough look at each cucumber you harvest and give it a good wash. Cut it open before just eating it right away to ensure there aren’t bugs inside the cucumber. For the cucumbers affected with something like blight, for instance, the cucumbers may be so rotten you wouldn’t eat them anyway. So when faced with a disease or a pest problem, make sure to inspect your product before consuming it. 

Final Thoughts

Black specks on cucumbers can mean a variety of different things. Luckily, the pests causing the black specks are not the end of the world. Although they may be annoying, there are many different methods of getting rid of them. The diseases are preventable, and it is always a good practice to use clean soil and clean garden equipment while gardening to ensure that no diseases are spreading around. Happy gardening!

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