Are you frustrated with seeing dents or holes in your cucumbers instead of smooth, healthy fruits?
When we put a ton of effort into growing food for ourselves or our families, losing even a single fruit can be heartbreaking. It’s especially frustrating when we can’t figure out what the problem is. That’s where this guide comes in.
If your cuke fruits are looking a bit holey, examine them well and try to rule out each of these issues in turn.
Below are 11 common causes of holes in cucumbers, and how to deal with them.
Causes of Holes in Cucumbers
1. Cucumber Beetles
If you’ve seen yellow and black striped or spotted beetles in amongst your cucumbers, then they’re likely at least one of the culprits for the holes you’ve been finding.
Cucumber beetles feed on Cucurbitaceae fruits such as cukes, melons, squashes, and pumpkins. They spread diseases while noshing on your precious plants and damage them throughout their entire life cycle, from larvae tunneling into roots and stems to adults eating the leaves and fruits.
Row covers can help to keep your cucumber plants safe, as can companions such as nasturtiums.
Planting a “trap crop” about 30 feet away can redirect the beetles’ focus elsewhere, and you can also pick them off manually and drown them in hot, soapy water.
Additionally, be sure to till your garden deeply in autumn to expose them to birds and other insectivores, and rotate your crops every two years.
Read more about cucumber beetles and how to eliminate them in our article.
2. Pickle Worms
If you’ve never heard of pickle worms before, you’re not alone—I hadn’t heard of them either until I found them in my beloved crystal apple cucumbers.
They’re the larvae of cantaloupe or squash vine borer (Melittia cucurbitae) moths, and they’ll wreak havoc on melon and cucumber fruits alike. Furthermore, since they tunnel into the fruits through the stems, they often do a lot of damage before they’re discovered.
Holes in cucumbers may be caused by these critters, as they have to create air holes for themselves to survive while they destroy your fruits from the inside.
If you see these holes, cut the fruit open to see if there are borers inside. There’s no real treatment for them other than destroying the fruit, rotating crops, and deep-tilling at the end of the season.
3. Anthracnose
If the holes in cucumbers that you’re spotting are dark and necrotic, you’re likely dealing with anthracnose. This pathogen thrives in cool, wet weather, so you’re more likely to come across it in the spring or autumn.
If you’ve dealt with it before, ensure that you solarize the soil well before planting, and treat the area regularly with neem or copper-based fungicides.
Aim to plant your cucumber seedlings once the weather has gotten hotter and dryer, and keep the plants pruned so there’s plenty of light fall and airflow. Keep the soil around them clear of detritus, and only water at soil level.
At the first sign of anthracnose, destroy infected plants and don’t grow cucumbers there again for at least five years.
Learn more about anthracnose in our article.
4. Cucumber Mosaic Virus
As with other mosaic viruses, this one can cause holes in cucumbers alongside the telltale “mosaic” patterns on the leaves and fruits. It’s transmitted by aphids and is so virulent that it can annihilate your entire crop if left unchecked.
There’s no treatment for mosaic virus, so all you can do if it appears is destroy any affected plants.
If you manage to harvest any fruits, don’t save the seeds (the virus will linger in them), and don’t plant any cucurbits in that area for at least five years.
If it’s an option, dig out all the soil in that area to a foot deep, solarize it on tarps, and work in well-aged compost before replacing it and planting a new crop. When you do plant cucumbers again, buy mosaic virus-resistant seeds from a reputable company.
5. Bacterial Soft Rot
Bacterial soft rot is caused by Erwinia carotovora , E. carotovora subsp. atroseptica, and Pectobacterium carotovorum bacteria, which thrive in hot, wet weather and can linger in the soil for years.
As such, if you live in a tropical climate or get very humid summers, you may have to deal with it ravaging your plants. You’ll recognize it as the cukes will be soft and spongy, with sunken, dark areas that smell quite foul.
Although bacterial soft rot can cause holes in cucumbers, it’s important to note that it can also enter the fruits via holes caused by other means.
If the fruits have been damaged by garden tools or insect predation, it leaves the fruits vulnerable to this type of bacterial infection.
You can try to treat this infection with copper-based bactericides or Streptomycin spray, but the best course of action is to detroy the plants and not sow cucumbers there for at least a few years.
6. Blossom-End Rot
If the holes in cucumbers that you’re dealing with are at the bottom ends rather than the sides, you may be dealing with blossom-end rot.
This issue occurs when there isn’t enough calcium in the soil during the plant’s flowering phase. After the flowers have been pollinated and the fruits start to mature, the blossoms drop off.
The problem here is that normally, the fruits’ skins seal up fully where the blossoms fell off. If there was insufficient calcium during flowering, however, the open wounds from the dropped blossoms don’t close up, but instead become infected.
This leaves open, gaping holes that rot quickly, rendering the entire fruit inedible.
Learn how to prevent blossoms end rot in our guide to this common physiological problem.
7. Animal Predation
I had been dealing with holes in cucumbers for some time and decided to rig up a camera for a few nights to see if I could find out what was going on.
In addition to the expected cucumber thieves, such as squirrels and raccoons, we discovered that deer and porcupines were also munching happily on our cukes.
Note that they weren’t actually eating these fruits: they were all simply biting into them and then going on their merry way to find items that were more palatable. Apparently, they just wanted to sink their teeth into them and ruin them for us before moving along.
If herbivores like these live in your area, consider putting up fences around your cukes to keep them from being gnawed upon.
Learn more about how to raccoon-proof your garden in our article.
8. Poor Pollination
If you’re wondering how pollination (or lack thereof) can cause holes in cucumbers, check this out: if a cucumber flower isn’t pollinated properly, this can result in deformed or incomplete fruit development!
As such, the “holes” you’re seeing in your cucumber fruits may be gaps and irregularities where the skin didn’t form properly as it grew.
To combat this issue, you can either get down and pollinate the cucumbers yourself, or sow pollinator-attracting species as companion plants nearby. Some of the best neighbors that will entice pollen-spreading bees and butterflies over to your cukes include:
9. Low-Quality Seeds
We literally reap what we sow, and if you planted old, poor-quality seeds, they might mature into sickly plants that produce misshapen, lumpy fruits that are full of holes, if they mature at all. Cucumbers grown from poor seeds may be stunted in size, lumpy, or pockmarked.
If this is the case, harvest what you can and process your cukes into relish or similar products that don’t require aesthetically pleasing shapes. Don’t save any of the seeds, and purchase high-quality ones from a reputable seed company or nursery next season.
10. Slugs and Snails
It should come as no surprise that slugs and snails will chomp holes in cucumbers. They’ll often leave trails or open wounds in the plant.
You’ve probably dealt with slugs and snails before, but if you’re looking for some advice on how to deal with them, please visit our guide.
11. Scab
Scab is a disease caused by the fungus Cladosporium cucumerinum. When the fungus infects your cucumbers, it causes small holes and sunken spots on the fruit. You might also see green spores on all parts of the plant.
Remove any symptomatic fruits and dispose of them in the garbage, not the compost. Then, spray the plant with copper fungicide. Repeat the treatment every two weeks until a week or two before harvest.
