What’s Eating My Broccoli (and Kale, and Brussels Sprouts…)?

Cabbage Moth Vegetable Garden

Do you see white butterflies, like this one near your kale, flittering around your garden each day?

Does your cabbage, broccoli, kale, or Brussels sprouts have holes in the leaves?

Pest Damage on Broccoli

Or maybe they look more like something was chewing on them for dinner…like this?

Worms on my broccoli

If so, the imported cabbage worm has likely taken up residence in your garden.

WHAT’S EATING YOUR BRASSICA PLANTS AND WHAT TO DO ABOUT IT

Cabbage, broccoli, cauliflower, kale, Brussels sprouts, kohlrabi, pac choi and mustard greens are all members of the same family – the brassicas. Plants that are in the same family are susceptible to the same diseases and pests in the garden. The biggest problem that gardeners all over the country face with brassicas is the imported cabbage worm.

The white butterflies can often be seen twirling and spinning right above your garden. They spend their days laying up to 300-400 eggs on the undersides of the leaves. Once hatched, the worms feed on both the inner and outer leaves of brassica plants, and can also be found boring into the broccoli florets and cabbage heads.

So, what do you do if you have cabbage worms?

Once they’re infesting your garden you have a few choices. As an organic gardener, spraying harmful chemicals is not an option in my yard. But, a treatment approved for certified organic use is Bt (Bacillus thuringiensis). Bt is a naturally occurring bacteria you spray on the leaves. It makes the caterpillars sick and eventually kills them when ingested. I’ve never used it in my own garden. I suggest you read more before using any chemical, organic or otherwise, in your garden.

Another option is to handpick the eggs and worms. This can be a lot of work if you have many brassica plants in your garden like I do. If you only plant a few and visit your garden often, this could be a great option for you.

I have the best luck seeing the worms and eggs in the morning or evening. Turn over the leaves and look for single eggs on the underside. They are tiny. Let me repeat…they are so tiny you can barely see them. See the photo below where I have one right by my thumb.

Broccoli Damage

When you find one, smear and crush it with your fingers.

The worms can be various sizes – extremely small and difficult to see, or fat and juicy and just right for squeezing!

Again, you’re looking mostly on the undersides of the leaves. They tend to hang out around the center rib of the leaf, near large holes, or anywhere you see little piles of dark worm poo (called frass).

I squish the little ones with my fingers, but the big guys can have an unappealing burst when crushed. I use a trusty old brick to smear or smash them against another hard surface.

What's Eating My Broccoli

  A tiny cabbage worm in the middle of the photo.

Worms on my cabbage

A big, juicy worm about to eat my purple cabbage for dinner.

A third option is to keep your plants covered with row cover for either part of or the entire season to prevent the moth from laying her eggs on your plants. I did this with a garden bed full of kale last season with great success. The kale leaves were pretty much perfect every time I harvested them. Not so with the kale that was left to fend for itself all season. It was riddled with holes.

kale under row cover in garden

My kale bed under row cover in late fall.

The kale left out to defend itself was destroyed by late fall.

This week, go out for a cabbageworm treasure hunt in your garden. Look for moths, eggs, and worms on your brassica plants. If you find some, decide which of the control options above you’re going to choose. I’d love to hear what you decide in the comments below this post!

Want to read more about summer challenges in the garden?

Top 8 Summer Gardening Challenges

Cut Down on Weeding in Your Summer Garden

How to Water Your Vegetable Garden in Summer

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Comments

  • I really enjoyed reading this! I think I will go on a bug hunt this week. This will definitely test my tolerance level..I might be willing to leave a few behind just to avoid the squishing and bursting experience. I think I’ll be walking softly and carrying a big brick. Great advice!

  • Jenifer Wilde-McMurtrie

    Have you tried diatomaceous earth?? EXTREMELY safe….

    • Hi Jenifer – Thanks for the suggestion. Bt works better on cabbage worms than DE. I used DE for the first time this year after a lot of reading. It does affect honey bees and other beneficial insects, so I don’t know that I would classify it as extremely safe. I would suggest using it with caution. That’s the tough part about treating our gardens, the things we use often affect all much more than the garden pests we’re trying to get rid of. I err on the side of letting nature take it’s course, for better or worse!

  • Thanks for the article! I am a first time gardener and have a lot of learning to do. I did notice little white butterflies hanging around our raised bed garden. I wondered was was eating holes in the Kale leaves. I checked the underside of the leaves and didn’t see anything. Of course it was in the middle of the day, and they were probably too small to see. Now I know what to look for. I may buy some of the row cover you talked about. I don’t want to harm any beneficial insects. Thanks for giving great advice!

    • You’re welcome, Roger! The eggs are teeny, so try looking for them again in the morning or evening. If you have the moth you definitely have the eggs. Good luck!

  • […] This past season, they destroyed my entire lacinato kale crop. Luckily, they don’t seem to bother the curly varieties, so I have still had plenty of usable kale. But, there are so many that it’s not practical to pick them off by hand after a few months. Next year I may experiment with keeping some kale under row cover for the entire season. (Read more about them here). […]

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