The cabbage white butterfly is drawn to brassicas (cabbage, cauliflower, broccoli, bok choy, kale…). A single caterpillar can decimate a young plant. Here’s how to get rid of cabbage worms in your garden — naturally.
Check out these natural methods for controlling some other garden pests, too!
Once upon a time, when I was a little girl, I proudly showed my grandma a wee sweet caterpillar. Instead of oohing and aahing over my find, Grandma snatched the wooly thing out of my hand and smashed it under foot. To her, it was simply a garden pest, but I was crushed.
I like to think that I’d never do such a thing in front of a child, but I can and do handpick pests in the privacy of my own garden. Cabbage whites – those pretty white butterflies that flit around home gardens in the summertime – can wreak havoc in a garden.
The other day a cabbage moth flew by. I did the logical thing and snatched it out of the air. There were no witnesses to my cruelty or to the fact that I’d snatched a moth right out of the air. I have turned into my Grandma, albeit a ninja version of my grandma.
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Identifying cabbage worms
There are a number of green worms that can plague cabbage and other brassica plants.
- Cabbage loopers are the larval stage of a grayish-brown moth. This worm has legs toward the front and the back of its body, but none in the middle. It moves in a characteristically “inchworm” style.
- The larval stage of the diamondback moth is much smaller than the cabbage looper or the cabbage moth, at about 5/16″ long.
- The cabbage worm is the larval stage of a cabbage white butterfly.
There are some similarities between the different pests. The adults flock to plants in the cabbage family, brassicas like cabbage, cauliflower, broccoli, bok choy, and kale, making it difficult to get these plants established in a garden. A single caterpillar can decimate an entire young plant, making them some of the most frustrating garden pests to deal with.
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Let’s focus on the one cleverly named “cabbage worm.”
Cabbage worm eggs
Cabbage moths are to brassicas as hornworms are to tomatoes. They are THE pest that you need to know about if you plan to grow brassicas.
White cabbage butterflies lay their eggs on brassica plants, often on the underside of the leaves. They are initially white, but turn yellow as they mature. The tiny eggs hatch in about seven days.
Cabbage white larvae
Tiny cabbage worms emerge from the eggs and begin immediately chewing on the leaves. The first telltale signs of damage will be shallow, grayish markings in the leaves. At this stage, the worms aren’t big enough to chomp all the way through a leaf. Not to worry, though — it will happen quickly enough!
Cabbage worms are a lovely velvety green. They blend in easily in a bed of green plants.
These worms tend to hide on or near the veins of leaves. When they’ve reached maturity at about an inch or 1-1/4″ long, they’ll pupate in preparation for their transformation into a cabbage white butterfly.
The chrysalis is often attached to the host plant or in nearby debris. In this case, it has attached itself to the planter my kale is growing in.
How to prevent cabbage white butterflies from moving in
An infestation of these pests can wipe out a young crop of cabbage or kale in days. Prevention is the best way to avoid that loss. There are a number of natural tactics you can use to prevent these pests from taking up residence.
- A floating row cover can prevent cabbage moths from accessing leaves on which to lay eggs, thus breaking the cycle. Another idea is to cover individual plants with upcycled mesh trash cans.
- Consider planting some cabbage moth trap plants to draw the cabbage worms away from your vegetable garden. A good choice in this case is a perennial tree collard. Planted some distance from your garden, you can let the moths go to town on these “sacrificial” plants.
- Interplanting brassicas with dill and lavender can deter cabbage butterflies. More on companion planting here.
- Give plants a good dusting of diatomaceous earth on a regular basis. Even if a butterfly manages to lay eggs on the plants, the soft-bodied caterpillars won’t stand a chance.
Signs that you have a cabbage worm problem
If you begin to see cabbage white butterflies flitting around your garden, it’s time to start watching your brassica plants for signs of the dreaded cabbage worm.
First though, grab an old tennis or badminton racket. It may seem gruesome, but I’ve had good luck swatting these flying pests out of the air. Killing them at this stage prevents them from laying eggs and interrupts their life cycle.
One of the best tactics for preventing cabbage worms is to check plants every few days for eggs and caterpillars. The earliest sign — and a chance to stop damage completely — are those tiny eggs. Check the underside of the leaves and wipe the eggs off.
Also look on the under side of the leaves and in leaf veins for tiny (TINY) green caterpillars and wipe those off as well.
Early damage will be hard to spot, but as the worms grow bigger, it will become more obvious. Chewed up leaves are a sure sign that you have a problem, but you might also notice tiny black droppings indicating that a cabbage moth has been eating (and pooping) on your plants.
Check the central vein of the leaves where it’s easy to miss the caterpillars. Giving the plants a good shake can dislodge cabbage worms, causing them to fall to the ground, but this isn’t a surefire method, as some will hang on tighter than others.
Instead of removing the chewed, ugly old leaves from the plants, try leaving them intact as bait for the cabbage moths. I’d rather have the caterpillars chewing on those than the young leaves.
Originally published in May, 2012.