Cabbage worms can destroy a plant almost overnight. If you’re seeing holes in cabbage, Brussels sprouts, or other cole crops, there’s a good chance the cabbage white butterfly or cabbage looper moth is to blame.
The caterpillars for these butterflies and moths love hide-and-seek. They'll hide under leaves and eat nonstop.
Getting rid of these garden pests doesn’t have to be complicated, but it does take consistency. Now, let's get rid of those goobers.
1. Get Used to Looking For These Pests
Cabbage worms come in more than one form. Most of them look like small, pale-green caterpillars, but there are a few species to watch for.
- The cabbage white butterfly (Pieris rapae) lays eggs that hatch into green larvae with a velvety texture. It's small, white, fluttery. Harmless-looking, but lays eggs daily.
- The cabbage looper (Trichoplusia ni) is another major pest, recognizable by its looping crawl and soft green body. It's brown and active at night. A member of the Family Noctuidae.
- The diamondback moth (Plutella xylostella) produces smaller larvae that wiggle when disturbed. It's slender, tan with a diamond pattern. Moves quickly when touched.
All of them go after host plants like cabbage, broccoli, cauliflower, kale, and Brussels sprouts.
A single cabbage worm can do a lot of damage, but it’s rare to have just one. You’ll usually find clusters of holes on the outer leaves first. If you find one, look underneath; you might find more worms or tiny yellow eggs stuck to the undersides.
2. Choose Natural and Organic Controls That Work
Chemical sprays aren’t your only option for pest control. Some natural and organic methods work just as well (sometimes better) when used correctly.
The most effective treatment is Bacillus thuringiensis (often shortened to Bt). It’s a microbial insecticide made from soil bacteria. It kills cabbage worms, loopers, and many other Lepidopteran pests without harming bees or birds. Caterpillars must eat it, so spray it directly on the leaves, especially the undersides. And don't forget to reapply it after rain.
Neem oil is another option. It doesn’t kill instantly but slows feeding and interrupts egg-laying. Use it early in the morning or late evening to avoid burning leaves.
Other natural enemies can help too:
- Parasitic wasps lay eggs inside cabbage worms. The larvae eat the worm from the inside. We don't like wasps either, but if you have them around, it's not always all bad.
- Ladybird beetles help with other soft-bodied pests that attract worms.
- Floating garden covers or agricultural mesh fabric keep adult moths away. We hate draping our whole garden with covers, but at certain periods of the spring and summer, it can help.
- Crop rotation also keeps pests from building up in one spot year after year.
Finally, after a particularly bad season, we ramped up our focus:
- We check the plants daily (field scouting helps spot problems early)
- I've placed pheromone traps to catch moths before they lay eggs. They seem to work? Fewer moths this year!
- I planted thyme and mountain mint in planters, and keep those plants nearby. They're strongly scented, which apparently moths don't like.
3. Keep Them From Coming Back
Getting rid of cabbage worms is only half the job. Keeping them out is just as important.
Try mixing up what you plant and where you plant it. Cabbage looper moths and cabbage butterflies are smart; they return to known host plants. Moving crops around, especially cole crops, helps confuse them.
Some gardeners switch from green cabbage to red cabbage, which tends to attract fewer cabbage moth caterpillars. Companion planting helps too. Interplant dill, oregano, or nasturtiums between rows of brassicas to throw off the scent trail moths follow.
Removing old plants is also important because worms and pupae often hide in fallen leaves. This is a good reason why cleaning up your garden at the end of the season can help. Those that survive winter can turn into adults next season and start the cycle all over again.
FAQ
Is the cabbage looper the same as the cabbage worm?
Not exactly. Cabbage worms are usually larvae of the cabbage white butterfly (Pieris rapae). Cabbage loopers are larvae of the cabbage looper moth (Trichoplusia ni), part of the Subfamily Plusiinae in the Order Lepidoptera. Both eat cabbage but have slightly different life cycles and body shapes.
Can cabbage worms harm other vegetables?
They sure can. While they prefer cabbage and Brussels sprouts, they’ll also go after broccoli, cauliflower, kale, and collard greens. These are all part of the brassica family, known as cole crops, and are frequent targets. They won’t usually eat things like tomatoes or carrots, but if you're growing lots of brassicas, they're a magnet.
