Cabbage worms are one of the most common pests in the garden. In this article, I’ll walk you through what’s really going on, and the simple, practical ways you can stop cabbage worms before they take over your garden and ruin your brassica crop.
How to defeat cabbage worms
Picture this: you’re outside admiring your garden, and everything looks great. Your plants are growing nicely, and you’re already imagining the meals you’ll make with your harvest.
And then the next morning, you walk out to your garden, take a look at your cabbage, and there are holes everywhere.
You think, “But they were fine yesterday! How could this happen overnight?”
Here’s the cause: cabbage worms.
Cabbage worms are one of the most common pests in the garden. And if you grow cabbage, broccoli, kale, or any of the brassicas, you’re going to deal with them at some point.
But here’s what I’ve learned after years of growing these crops:
This isn’t something you want to react to - it’s something you want to stay ahead of.
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| Visible damage from cabbage worms. |
What are cabbage worms?
Those pretty white butterflies floating around your garden in the spring?
Those are cabbage butterflies (sometimes called cabbage moths), and they’re laying their eggs on your plants - usually on the underside of the leaves, where you don’t see them.
Those eggs hatch into small green caterpillars - what we call cabbage worms - and they start feeding almost immediately.
They’ll go after cabbage, broccoli, cauliflower, Brussels sprouts, kale, and collards. They’ll also chew on radishes and turnips.
Cabbage worms vs. cabbage loopers
You might also hear gardeners talk about cabbage loopers. They are different pests, although they target the same plants and cause similar damage.
Cabbage worms are slightly smaller than cabbage loopers. They’re soft green caterpillars that crawl normally. They come from those familiar white butterflies you often see fluttering around the garden, and they usually leave smaller, scattered holes—often on the undersides of leaves.
Cabbage loopers are light green caterpillars that move in a distinctive looping motion, arching their bodies like an inchworm as they crawl. They come from a brown moth and tend to chew larger, ragged holes in leaves.
Since cabbage worms and cabbage loopers are similar pests and cause similar damage AND you deal with them in the same ways, I’m going to lump them both together today and refer to them all as “cabbage worms.
What cabbage worm damage looks like
At first, you might not notice anything, but before long, you’ll start seeing:
- Holes in the leaves
- Ragged edges
- Small dark droppings on the plant
And once they get inside the head of a cabbage, that’s usually the end of it.
That’s why the key isn’t just dealing with cabbage worms - it’s catching them early, or better yet, preventing them altogether.
Your First Line of Defense: Pay Attention
One of the simplest and most overlooked things you can do is just get in the habit of checking your plants.
When you’re out watering or weeding, take a moment to flip a few leaves over and look for:
- Tiny yellow eggs
- Small green caterpillars that blend in with the leaves
You can pick them off by hand and drop them into a jar of soapy water. This does work, but let’s be honest, it gets old fast.
And if that’s your only strategy, you’ll always feel one step behind.
The Most Effective Solution: Cover Your Plants
If you do nothing else to prevent cabbage worms, do this: cover your plants.
Here’s the secret: if the cabbage butterflies can’t reach your plants, they can’t lay eggs. And if there are no eggs… there are no worms.
You can use:
- Insect netting
- Row covers
- Nylon mesh (even inexpensive fabric store netting works)
Set up a simple low tunnel using wire hoops, fencing, or anything you have on hand. Then drape the netting over the top and secure it along the edges so nothing can sneak in.
Sunlight still gets through. Rain still gets through. And your plants grow just fine, safe inside their protective tunnel.
Because cabbage and other brassicas are harvested before they flower, you don’t need pollinators for these crops - so it’s perfectly fine to keep them covered right up until you're ready to harvest.
This one step will make the biggest difference in your garden.
Companion Planting
Companion planting isn’t magic, but it can help. Think of it as adding another layer of protection.
Some plants seem to confuse or repel cabbage butterflies, making it harder for them to find your crops.
Some companion plants also attract beneficial insects to your garden, which is why I suggest it in addition to covering your plants.
One of my favorites is catnip. It has a strong scent that can help mask your cabbage plants, and it also attracts beneficial insects.
Other helpful companion plants include:
- Thyme and sage
- Onions and garlic
- Nasturtiums (which can act as a trap crop)
- Borage and rosemary
These plants might not stop every cabbage worm, but when you combine companion planting with row covers and regular checking, you’re stacking the odds in your favor.
Organic Sprays: A Supporting Tool
If you prefer organic methods (as I do), you can also use sprays to help repel cabbage worms. One simple option is a homemade garlic spray made with:
- 1% minced garlic
- 1% fish oil
- 98% water
Let the mixture sit overnight, strain it, add to a spray bottle and spray it on your plants.
This won’t kill cabbage worms, but it can help repel them and reduce damage. You'll need to reapply it regularly, especially after rain.
Organic-approved sprays for cabbage worms
As a last resort, you might want to use Bt (Bacillus thuringiensis), a naturally occurring soil bacterium that’s approved for organic gardening. But there are different types, and for cabbage worms and cabbage loopers, you need Bt kurstaki, often labeled Bt-k. The package will probably state “for caterpillars.”
This is the type that targets caterpillars, including cabbage worms, cabbage loopers, and tomato hornworms. When the caterpillars eat treated leaves, they stop feeding and die.
However, Bt doesn’t know the difference between pests and beneficial caterpillars. It will affect all caterpillars, including butterfly larvae, so it’s best used carefully and only when needed.
Bt is considered safe for birds and other wildlife. But in my own garden, I try to step back and look at the bigger picture. Caterpillars like cabbage worms and loopers aren’t just pests—they’re also food for birds. When we remove them completely, we’re also removing part of the natural system that helps keep everything in balance.
Personally, I’d rather have birds and butterflies in my garden, so I rely on prevention rather than eradication. (Yes, even the pretty white butterflies that lay eggs that hatch into cabbage worms.)
That means I accept a little bit of damage here and there, because I know those birds are helping me in ways I can’t always see. Over time, that balance makes a difference.
If you do need to step in, Bt is a reasonable option—but think of it as a backup plan, not the first line of defense. If you choose to use it, apply it in the evening, spray both sides of the leaves, and reapply after rain for the best results.
Let Nature Help You
A healthy garden isn’t just plants: it’s an ecosystem. There are plenty of beneficial creatures that help control cabbage worms for you, including:
- Braconid wasps
- Damsel bugs
- Ground beetles
- Spiders
- Frogs and toads
- Birds
You can encourage these helpers by planting a variety of herbs and flowers and creating a garden that feels alive and balanced.
Your simple plan
A few simple mistakes can make cabbage worm problems worse, especially waiting until you see damage before taking action, and not checking the undersides of your plants' leaves regularly.
A little prevention goes a long way. Adopt this plan to keep your cabbage and other brassica crops safe from cabbage worms:
- Cover your plants: Using row covers is the single most effective way to get ahead of the cabbage worm problem. For the best results, cover your plants as soon as you transplant them into the garden, or right after you sow the seeds.
- Check your leaves when you’re already in the garden
- Add one or two companion plants nearby
Every gardener deals with pests - it’s just part of growing your own food.
With a little planning and a few simple strategies, you can grow healthy, beautiful cabbage without cabbage worm damage, and actually enjoy the process.
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Kathi Rodgers is the gardener and writer behind Oak Hill Homestead (est. 2006) and the host of HOMEGROWN: Your Backyard Garden Podcast. With over 30 years of gardening experience in a variety of climates and soils, she helps new and aspiring gardeners grow healthy, organic food right in their own backyards.
A passionate advocate for simple, self-reliant living, Kathi is the author of multiple ebooks, a published magazine contributor, and shares practical advice with readers who want real-life solutions they can trust.
Kathi lives in Oklahoma, where she grows more cherry tomatoes than she can count and keeps a watchful eye on tornado season. A proud grandma and great-grandma, she believes that wisdom - like a bountiful garden harvest - should be shared.
