Natural Ways to Control Cabbage Worms
What Is Eating My Vegetables?
Harvesting and enjoying the fruit of one’s labor is a rewarding and satisfying feeling every gardener growing their own food should experience. We browse through colorful seed catalogues all winter long, strategically planning what and where to plant it all. There’s nothing like taking a stroll through the garden, picking a little of this and a little of that, and preparing a delicious, healthy, and affordable meal for your family.
And there is no greater frustration and feeling of defeat when you arrive at your little oasis of food to find that something has already eaten your salad. Many put up fences and scarecrows to guard precious crops from deer, rabbits, birds, and other animals, but caterpillars can do just as much damage.
One particularly bad one that is known for destroying many crops is the cabbage worm.
Did You Know...
Cabbage worms don't only eat cabbage. There's a long list of cruciferous vegetables in the Brassicaceae family that they enjoy.
What Does a Cabbage Worm Look Like?
Not all caterpillars are bad; some are actually very beneficial, so before you start exterminating, be sure you've identified the caterpillar properly.
- Cabbage worms are velvety green larvae that grow to be about 1 1/4 inch long. If you look really closely, you may see some tiny black or yellow markings. They sometimes linger on the undersides of leaves, out of sight of predators, but they are very hungry and spend their days nibbling around and boring into leaves, spreading out the damage they do to the plant.
- Cabbage white butterflies are what they grow into, which are mainly white but with a few black markings with a wingspan of 30 to 47 mm.
- Eggs: They lay their very small and yellowish or leaf-green eggs on the undersides of leaves, and you probably won't notice them, even if you're looking really hard.
- Other signs: Sometimes, it's not the caterpillars that you first notice but the damage they do to the plants. Wormholes and dark green droppings are signs to look for.
Natural Ways to Get Rid of and Control Cabbage Worms
So how do you get rid of these cabbage worms in a way that is safe and effective? If you are growing food, you most likely do not want to be using chemicals, since you want to keep it as clean, healthy, and organic as possible. Well, there are several natural remedies and methods you can use safely.
- Plant garlic, allium, thyme, tomatoes, onions, sage, borage, nasturtium, tansy, and rosemary near the affected plants, as they are known to deter cabbage worms. Plant flowering plants and herbs nearby to attract natural predators.
- There are plenty of other insects you can attract to the garden that attack these worms, such as spiders, ground beetles, yellow jackets, and wasps. The braconid wasp will prey on these caterpillars all day long.
- Their predators include the house sparrow, skylark, and goldfinch skylark, so if you can attract those birds to your yard, you can enlist their help.
- Crop rotation will help reduce future pest populations. This means every so often, you plant a different type of plant in that section of your garden.
- Be sure to remove old and dead plants quickly. In its pupa stage, the caterpillar will over-winter in plant debris such as this.
- Tilling the soil several times between planting will help destroy the eggs and pupa as well.
- Hand-picking the worms off will slow an infestation (but if your infestation is anything like the one I had on my kale last season, you will never win). With gloved hands, pick them off at least once a week. (You can crush them or drown them in a jar full of soapy water.)
- Cover your plants with lightweight nylon so that the butterflies cannot lay their eggs on the plant's leaves. (Do this before you see any signs of the pest since this same net might prevent natural predators from eating the worms.)
- There are some natural and organic applications. Sprinkling dry cornmeal or rye flour on damp leaves will kill the worms. After they eat it, they bloat and die. You can also use diatomaceous earth.
- An organic spray that is very popular amongst many growers is Bacillus thuringiensis or BT, which is a natural soil-borne bacterium that has been used as a natural insecticide for over 50 years and has been proven to be very safe for the environment and humans. If you see any cabbage butterflies, start using BT weekly. Spray it on your plants in between waterings, so it doesn't get washed off too quickly.
- Make your own spray repellant. See recipe below.
Make Your Own Cabbage Worm Repellant Spray
- In a blender, combine any combination of the following ingredients: garlic, mint, onion, hot peppers, horseradish, and/or mineral oil.
- Mix in an equal amount of water.
- Strain. Sprinkle the solid stuff under the plant and put the liquid into a spray bottle.
- Add a tablespoon of liquid soap.
- Spray it onto your plants in between waterings.
What Do Cabbage Worms Eat?
- Bok Choy
- Brussels Sprouts
- Mustard Greens
What Do Cabbage Butterflies Eat?
They like blue, purple, and yellow flowers the most. They are less attracted to flowers that are white, green, or red.
What About Those Little Dark Caterpillars or Inch Worms Eating Your Vegetables?
Cabbage worms are not the only type you might find eating your vegetables. These other two pests are common:
Cabbage Loopers (Trichoplusia ni)
- As larva: Loopers (aka inchworms) are easily recognized by the way they move: They double up (or “loop”) as they inch along. They have six legs: Three in the front and three behind (but none on their middle, looping segments). They are plump, soft-looking, and pale green with two slim, white, lateral stripes and grow to be about an inch and a half long.
- As adults: These are nocturnal, mottled brown or gray, with an inch and a half wingspan. Each forewing has a silver, v-shaped spot.
Diamondback Moths (Plutella xylostella)
- As larva: They start small and brownish with a forked-looking tail and quickly turn pale or bright green with a darker head. They have ten legs, and the hindmost protrude to form a v-shape. These larvae are quite active and may wriggle violently when disturbed.
- As adults: Also known as cabbage moths, these nocturnal night-flyers are small (15 mm from wingtip to wingtip), slim, and grayish-brown with pronounced antennae.
Extermination methods for these two are generally the same described for cabbage moths above.
What If You Accidentally Eat a Cabbage Worm? Are They Poisonous or Dangerous to Humans?
These little green caterpillars are completely harmless to humans and pose no danger, even if you accidentally ate one. In fact, they are a sign that your vegetables are probably organic, since chemicals would probably have killed them. If you find them on your food, just wash them off.
Where Did the Cabbage Worm Come From?
The cabbage worm came from Europe and is believed to have arrived in Massachusetts about 1869, and then quickly spread throughout the rest of the United States. Members of the brassica or mustard family are its main targets.
The cabbage worm is the larval form of the cabbage white butterfly (Pieris rapae), which is white with specks of three to four black spots on each wing. These pretty white butterflies lay little yellow eggs on the underside of leaves. Within a week’s time, these eggs hatch little green caterpillars that immediately start munching away on your precious kale, cabbage, broccoli, and cauliflower, leaving ragged holes in the leaves. They will continue feeding for 2-3 weeks, and then pupate, having between three to six generations in one season.
If you haven’t noticed any damage to your plants, but see these little white butterflies flying around, start taking action! Make sure to check the underside of the leaves. This is where they like to lay those eggs, and even when they become worms they are so hard to see, they blend in so perfectly.
Remember to Check Underneath the Leaves!
Remember to always check and spray underneath the plant's leaves. There were so many occasions when I thought I had all of them removed, until I turned a few leaves over. They blend in so well! If you see the white butterfly flying over your crops, take immediate actions, and start inspecting your plants and try to prevent any future infestations.
Chances are if you're reading this article you most likely are a gardener, and have experienced a few run-ins with these guys. I am curious to know of some more natural ways to get rid and prevent these worms. I lost nearly my entire crop of kale to them last year and want to avoid that as much as possible. Please share with me if you have any experience in dealing with the cabbage worms by leaving a comment below. Thanks, and may we all have a great growing season!
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
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© 2011 rpalulis