A cabbage worm is a common pest for common vegetables that we enjoy including the cabbage family. This pest can damage your crop, but if you know how to identify them, get rid of them, and prevent cabbage worms in the future, there is no need to panic.
Before discussing how to get rid of cabbage worms using natural or chemical methods, let us take a closer look at these unwelcomed creatures.
What Is Cabbage Worm?
The cabbage worm’s scientific name is Ascia monuste, but it is also known by many other names such as gulf White cabbage worm, imported cabbageworms. Adult butterflies (they are not moths) are also called cabbage whites or small whites. Pieris rapae or Artogeia rapae are its Latin names too.
Originally from Europe, cabbage worm eggs are mainly a problem for cabbage plants (Brasscica oleraceae) like cabbage, kale, cauliflower, broccoli, etc., causing serious damage to the foliage.
These plants can handle such damage, but during cold seasons (in the seedling establishment or early head formation), cabbage worm caterpillars are the most harmful to the crop’s growth and yield.
Note: While these butterflies are not moths, they are also not worms but caterpillars.
What Do They Look Like?
If you want to know how to get rid of cabbage worm and wipe them out successfully, you should not mistake them for other pests.
Cabbage worm larvae are green and as you can see in the pictures, they have a velvety look. It is easy to confuse them with cabbage loopers. However, the latter is yellow-green caterpillars that, unlike Ascia monuste, raise and lower their bodies when moving since they do not have middle legs.
Tip: Next to cabbage loopers and worms, you may also find diamondback moth and the zebra caterpillar eggs or larvae in your garden. They are amazing at camouflage since most of the time you can only see the fecal matter that they leave behind.
Cabbage worm caterpillars turn into cabbage white butterflies that are white for the most part with a few black markings. Females display two black spots on each forewing, while males have only one spot. From the outside, they seem a playful addition to the gardens. Bet, it does not change the fact they are laying eggs on the back of the cabbage leaves.
Cabbage Worm Life Cycle
The cabbage worm life cycle begins when the female white butterfly lays the eggs on the undersides of leaves. The eggs are bullet-shaped, elongated, and yellow in color.
When they hatch after 7 to 12 days, the larvae measure 1 mm and have a greenish-yellow color. After a few days, they take on a light green color with black dots and a few yellow lines on the back. The cabbage worm larvae reach their maximum development at 21 days, measuring 4 cm long.
After feeding heavily for 15 or more days, the worms pupate for 10 days during late spring and summer, and a new generation of butterflies emerges. They generally live for a couple of weeks, sometimes as long as 3 weeks. There are 3 to 5 overlapping generations each year. And if you live in warmer areas, you may see up to 8 generations.
What is The Cabbage Worm Damage and Its Signs?
As mentioned earlier, cabbage worm damage includes the loss of foliage. If unnoticed, they continue eating away, leaving your plants only with stems and large veins. They can eventually kill the plants by destroying their ability to photosynthesize.
Sometimes the damage is only cosmetic, but if one does not know how to get rid of cabbage worm, they can devour the crops as well as contaminate them with their dark green, round, pelleted fecal matter (called frass) also known as the cabbage worm poop! And as mentioned, they can be devastating to
If you see holes in the leaves or flower stalks, skeletonized leaves, and their excrement, you need to find an effective method for controlling these creates. Before reviewing the options, let us answer another important question:
Are Cabbage Worms Harmful to Humans?
While ingesting worms has no specific benefits for humans (besides a little bit of extra protein), cabbage worm damage does not extend to humans. You may have heard some stories about these caterpillars causing problems for the brain, but they are all misconceptions.
How to Get Rid of Cabbage Worm?
To ensure no toxic effect on humans, birds, pets, bees, or other beneficial insects,
Remove Them by Hand
If you are okay with handling these pests, you can try manual removal. It may not seem like it, but in the case of some pests like cabbage worm caterpillars, and when growing a handful of plants, manually removing them upon noticing is sometimes the quickest and easiest way to get rid of them.
All you need to do is hand-picking and collect the caterpillars from brassicas and leafy greens and remove them somehow. For example, you can give them to chickens or squish them. If you are going to dedicate yourself to this method, we recommend inspecting your vegetables frequently (once or twice per week).
When inspecting, keep in mind that often you can find cabbage worm eggs and worms underside of leaves or in the new growth at the plant’s center. Check the center vein of kale leaves for sneaky ones. And finally, cabbage worm poop is a strong indicator that caterpillars are nearby. Additionally, if you see any tiny oblong white to yellow eggs underside of leaves, wipe them away.
Introduce Beneficial Insects
Sometimes, you do not have to personally intervene to drive this pest away. There are beneficial insects like parasitic wasps that can help you with that.
This species lay its eggs inside or on top of other arthropods like caterpillars and their pupae. And once the eggs hatch, the wasp larvae feed on the host caterpillar and kill it.
There are dozens of types that can help you minimize cabbage worm damage and even other pests like tomato hornworms. We recommend buying a starter community of Trichogramma wasps to introduce to your garden that, unlike other large wasps, do not bite or sting either.
Use Yellow Sticky Traps
Set these traps in different parts of your garden to catch adult butterflies. However, consider that they can catch beneficial insects too.
Use Bacillus Thuringiensis (Bt)
‘Bt’ is a naturally soil-dwelling bacteria found on leaves and in soil worldwide and a frequent ingredient in organic biological pesticides. ‘Bt’ kills caterpillars by making them stop eating. However, it is toxic to butterflies or moths’ larvae. Therefore, Bacillus Thuringiensis is commonly used to control cabbage worms as well as cabbage loopers on brassica plants. Let us see how to get rid of cabbage worms using Bt.
You can find pre-mixed Bt sprays or as a concentrate that must be diluted before applying. We recommend the second option as they offer better results. As mentioned, Bt is completely safe for humans or other mammals, even if sprayed the same day as harvest. It also rapidly degrades in sunlight and washes off with water or rain.
Here are some tips when using this method:
- Mix the concentrate well directly in your pump sprayer.
- Apply the Bt solution in the evening hours.
- Spray the plants including the bottom of leaves until dripping.
- Avoid over-spraying the plants onto non-target areas.
- Bt is most effective against small cabbage worm caterpillars, so treat caterpillar-infested plants early on. You may need to remove the larger ones manually.
Sprinkle Cornmeal or Rye Flour
Some say that dampening cabbage leaves and sprinkling them with cornmeal is an effective way to get rid of cabbage worms. The idea is that the pests eat the cornmeal, swell, and die.
There is also a piece of old advice about sprinkling rye flour over cabbage plants in the early morning, which dehydrated the worms.
This is a powerful response to how to get rid of cabbage worms. Always use the pesticides that have the least toxicity. If using Bt was not helpful, try another pesticide when the worms are large or digging. Piretrina, which is plant- or bacteria-based, is a good option. However, they might be harmful to beneficial insects.
There are stronger options like esfenvalerate, lambda-cyhalothrin, Acetamiprid, permethrin, carbaryl, endosulfan, and malathion. But they affect all insects and should not be drained in any body of water.
How to Prevent Cabbage Worm Caterpillar?
To prevent this problem in the future, try the following methods. You can also combine them with the methods for getting rid of Ascia monuste for maximum effect.
Apply Neem Oil
Neem oil is not only the answer to “How to get rid of cabbage worm?” This plant-based oil is effective against many pests. This organic pest control is perfect for controlling small insects with soft bodies like aphids, spider mites, mealybugs, scale, etc. as well as cabbage moths, mosquitoes, and flies.
Simply dilute concentrated neem oil and spray it onto plants routinely. It coats the cabbage worms’ bodies, and interferes with their reproduction and feeding, killing them eventually. Keep in mind that if your plant is already infested with this pest, neem oil will not typically kill them.
Use Decoy Cabbage Moths
Looking for quick ways in “How to Get Rid of Cabbage Worm and Prevent Them” lists? Try this method. Apparently, Ascia monuste are territorial. That means that if they see cabbage whites around, they will stay away from that territory.
Using this tip, there are gardeners that successfully deter these pests by placing decoy white butterflies around their garden beds. Make your own dummy butterflies using printable templates found online and (with some luck) save your garden in no time!
Cover the Plants
If the pests cannot reach your plant, they cannot damage it! Row cover is the best way to protect the plants and block out pests, incest, squirrels, rabbits, neighborhood cats, wild birds (that mainly attack young seedlings), or other undesirable elements. In addition to preventing cabbage worm damage, they are used for frost protection and to provide shade.
How to get rid of cabbage worm using floating row cover you ask? You can use sleek hoops (short or long depending on the bed width and the height of the plants), insect netting, and base extenders. You can also make customized hoops using PVC pipes. Also, make sure to check the various sizes of netting to find the size that fits your garden the best.
They work great at stopping these pests (especially when using the right material and tucking the corners and sides in tight) while offering easy pull-back for harvesting. The downside of this method is that along with cabbage worms, pollinators cannot reach your plant as well.
Although the cabbage family does not need pollination to grow, if you are growing flowering plants like squash, this might be a problem. In this scenario, open and close the covers daily or hand-pollinate them.
Plant Cabbageworm-Resistant Varieties
If you are open to planting purple and red varieties, you do not need to worry about cabbage worm caterpillars anymore. Since pests are generally less attracted to red and purple vegetables, another idea is planting varieties like purple cabbage and red kale.
But what is the reason? One theory is that green or pale-colored pests cannot disguise on vegetables with bright colors, making them easy targets for predators. Studies also show that anthocyanin (the antioxidant-rich flavonoid in red, purple, and blue-pigmented vegetables) is mildly toxic to caterpillars. This could even help in deterring larger pests like squirrels.
Try Companion Planting
A little diversity benefits everyone and what way better than polyculture (growing various plants in one space) to introduce diversity in your garden. This way you can maintain balance, attract more beneficial insects, and minimize the chances of widespread devastation by pests like cabbage worms.
So, consider interplanting some companion plants that deter cabbage moths (like thyme, dill, oregano, lavender, onions, garlic, and marigolds) with brassica that are susceptible to pests. You can also use companion plants (like Nasturtiums) as trap crops that lure cabbage worms away from other vegetables.
If you chose the latter option, remove infested trap crops regularly to prevent a swarm of cabbage moths in your garden, or remove and kill the caterpillar by hand from the trap crops.
What is your experience with cabbage worm caterpillars and their potential damage? What did help you to get rid of them? Let us and other readers know in the comments.