Cabbage worms are the larval form of cabbage butterflies, and just like you may have been taught in grade school, they can eat through a significant portion of your veggie garden! They are constantly growing, and their one focus is on feeding as much as possible.
Cabbage worms love to eat veggies and will focus on broccoli, cauliflower, brussel sprouts, mustard greens, kale, collard greens, radishes, tomatoes, potatoes, and even squash and watermelon. Luckily, they can be controlled with manual removal, natural cabbage worm predators, and insecticides.
Luckily, there are many steps you can take to deter or eliminate cabbage worms from your garden. These tenacious pests can have multiple generations in a year, so you will need to be both thorough and consistent to completely eradicate them from your garden.
Why Are Cabbage Worms On My Plants?
The biggest question you may have is why cabbage worms are in your yard and plants in the first place.
These garden pests are prolific across North America and internationally, and have been problem insects for hundreds of years and many generations of gardeners.
Cabbage worms develop into butterflies, and they are able to distribute their populations far and wide once they grow wings.
Adults will seek out gardens that contain the plants they love. They will lay eggs right on the leaves in order to give their young the resources they need as they grow and develop.
So what exactly is attracting cabbage worms to your yard?
Cabbage Worms Love To Find A Bite To Eat
Like we discussed, cabbage worms are voracious eaters, like other caterpillars. Foliage is the main food source for cabbage butterflies, and they will often eat away all but the stems and veins of an infested plant.
Cabbage worms will show preference for and can do the most damage to young plants, but they will not shy away from mature plants and can still do serious damage.
As the worms get larger and closer to adulthood, they have even been known to burrow down into the heads of broccoli, cabbage, or other greens where they find safety and build chrysalises.
Because these pests have specific nutrient needs that are found in the plants they eat, cabbage worms will seek gardens that have a plethora of these cruciferous veggies growing.
Further, because they will often have up to four generations per season, plus overwintering larvae, cabbage worms are likely to stay in one place once they find a reliable food source.
Your Yard May Be Providing Them Safety
Cabbage butterflies have many natural predators, and your yard may actually be protecting them from predation if you are reducing natural biodiversity of insects and birds who may actually be helpful in reducing their populations.
Additionally, if you are leaving up previously eaten crops and infested beds, you may be increasing their overwintering survival rates.
Remove old and spent crops over winter to reduce sites that they will be using for protection during the colder months, according to the University of Minnesota.
Leaving weeds, especially those in the Brassicaceae (Brassica) family such as wild mustard, peppergrass, garlic mustard, and marsh cress can serve as desirable food sources in the absence of more traditional crops. Excessive weeds and plant debris can actually create a safe environment for pest insects to hide in.
They May Be Laying Eggs In Your Yard
The most likely reason you are seeing cabbage worms in your yard is because the adult butterflies are laying eggs in your garden and especially on host plants.
These butterflies take to the wing to travel far and wide to seek out gardens with a plethora of host plants to give their offspring the best chance of survival.
According to South Dakota State University, us that cabbage worms will generally reproduce two to three times per year, but can have up to four generations in one growing season.
This is why you should be consistent when applying any control technique, as cabbage worms will continue to reproduce and likely have another generation brewing before you have even eliminated the first.
South Dakota State University goes on to warn that the presence of these butterflies is often the first indication you will have that a cabbage worm infestation is afoot.
You can identify the butterflies by their distinctive white coloring with dark spots on the inner and outer edges of the wings. When you see them land on the target plants, you can assume they are likely laying eggs there.
What Plants Attract Cabbage Worms?
Now that you know why cabbage butterflies are seeking a home in your yard, you may be wondering exactly which plants they are after. Read on to discover the ten main plants that attract cabbage worms!
1. Cabbage Worms Generally Love Brassica Family Plants
It seems obvious since it is in the name, but cabbage worms target mainly plants such as cabbage and other members of the Brassicaceae (Brassica) family. The primary target plants of cabbage butterflies will include cruciferous veggies with thick, green, glossy foliage.
Though they will focus primarily on these specific plants, cabbage worms have been found to go for other plants when their preferred varieties are unavailable including tomato, potato, and even squash and watermelon leaves.
When the cabbage worms feed on these alternative foliage types, they can actually cause damage to the vegetable itself by cutting off the plant’s energy supply by eating the portions that photosynthesize.
2. Broccoli And Cauliflower Makes A Yummy Treat For Caterpillars
These hearty veggies are part of the Brassica family, and cabbage worms will munch the thick foliage of broccoli and cauliflower. As they mature, cabbage worms will actually burrow down into the heads of the veggies, eating their way through to the inside.
Here, they will build up their pupa, which are less than an inch long and a faded green or yellow and brown in color.
Inside of these plants the pupa find safety and shelter as well as an ample food supply when they emerge.
3. Cabbage Worms Love Cabbage!
It probably comes as no surprise because of their name, but cabbage worms love cabbage. From the dense heads to the thick, green foliage, cabbage worms will devour every part of the cabbage.
If you have a cabbage worm infestation, make sure to check your harvested cabbage and other related veggies closely for pupa and cabbage worms that may be hiding within the folds of the cabbage head.
You should soak your harvest in salt water for an hour or longer and then wash your produce thoroughly to get rid of any lingering pests you may have missed.
4. Cabbage Worms Adore Mustard Plants
This may come as a surprise, but mustard plants are actually a part of the Brassica family, closely related to cabbage, kale, and broccoli. Cabbage worms will go to town if you have these less common plants in your garden.
Some gardeners even plant mustard as a decoy to lure the cabbage worms away from more coveted plants they are hoping to protect.
You can plant a crop of cold hardy mustard greens and wait for the cabbage worms to take over them, then cut the whole plant down and dispose of the pests in a bucket of soapy water.
5. Kale, Collard Greens, And Other Greens Can Attract A Lot Of Cabbage Worms
Cabbage worms love thick, green or red, shiny foliage that is common in the Brassica family. It makes sense, then, that they are especially attracted to greens like kale and collard greens and sometimes even spinach.
It is quite remarkable how efficient cabbage worms are at taking down these leafy greens, stripping them down to the woody stem and veins, eating all of the tasty bits in between.
Check carefully on the undersides and toward the center veins of these leaves, where cabbage worms may be seeking shelter out of sight.
If you’d like more info, take a look at our full list of insects that love eating kale!
6. Cabbage Worms Will Eat Radish And Turnip Greens
Even though cabbage worms will ignore the root vegetable underground, radish or turnip greens make a tasty treat for the small pests. They will sometimes go after the leaves of other root veggies.
While this may seem innocuous, by munching away at the above-ground portion of these plants, cabbage worms destroy the photosynthesising part of the plant and can actually stunt the growth of the radish underground.
7. You Hate Brussel Sprouts, But Cabbage Worms Love Them
Brussel sprouts might not be the most popular vegetable, but cabbage worms would never turn up their nose at this member of the Brassica family.
Brussel sprouts have everything a hungry cabbage worm could want from small cabbage-like heads to plentiful foliage, and many cracks and crevices to hide within.
8. Some Cabbage Worms May Eat Tomatoes
Cabbage worms will even go for plants outside of the Brassica family if their preferred veggies aren’t available. Cabbage worms have been known to target the foliage on tomato plants.
Even though the pests are unlikely to go for the fruit of the tomato plants, feeding on the foliage can still affect the entire plant by inviting disease, fungus, or other pests into the wounds left behind on partially eaten leaves.
Additionally, damage to the foliage means the plant has less surface area to absorb energy from the sun!
9. Cabbage Worms Have Been Known To Eat Potato Leaves
Similarly to tomatoes and radishes, cabbage worms will also gladly populate potato leaves with the same potential for damage.
Cabbage worms have even been known to go for squash and watermelon if nothing else is available!
How To Get Rid Of Cabbage Worms On Your Plants
Cabbage worms are tenacious once they become established, and can reproduce up to four times in a single season.
For this reason, you need to be diligent about catching them early and consistently check for new generations throughout the growing season as new adults come into your garden and missed eggs develop into adults.
Read on for some tips on how to remove existing cabbage worms and prevent adults from laying new eggs on your plant.
If you’d like a more detailed list, take a look at our list of the things to do if you have cabbage worms in your garden! Otherwise, hang tight!
1. Prevent Adults From Laying Eggs On Host Plants
One of the most important cabbage worm control methods is to prevent the breeding adults from landing on and laying eggs on your plants in the first place.
A good idea is to grab some plant covers, like these Flarmor Floating Row Covers.
Install these or make them yourself using stiff wire and open mesh material. These covers will prevent the adult butterflies from landing on your plants at all.
They also have the added benefit of protecting your plants from other airborne pests and even freezing temperatures or scorching heat waves.
The drawback of this method is that these covers will also prevent beneficial insects and pollinators from reaching your plants, so you might want to limit their use to only when you know you have adults in the area.
2. Manually Remove Them From Your Plants
Despite how laborious this method can be, the most effective way to rid your plants of cabbage worms is to manually pluck them off of the plants and drop them into a bucket of soapy water.
Cabbage worms move sluggishly slow and will not flee in fear because they will be distracted by the feast they are residing on, so it is actually quite easy to pluck them one by one. If you are squeamish, you should glove up! These worms are squishy and slimy!
If cabbage worms have already ravaged a particular plant or set of plants, you may even want to just cut the infested plant down or prune it back aggressively to spare the rest of your garden from being taken over.
Make sure to dispose of the plant in a closed bin or soak it in soapy water to eliminate the pests and prevent them from finding their way back to the garden.
3. BT Is A Natural Cabbage Worm Solution
BT is short for Bacillus thuringiensis which is an organic bacteria-based insecticide according to the University of Maine and is especially effective in warm spring or summer weather, when the cabbage worms are most active.
Studies by the University of Florida have found these formulations to be particularly effective insecticides when it comes to cabbage worms and other types of caterpillars. As with most insecticides, BT is most effective on young cabbage worms as opposed to more mature specimens.
BT is organic and products like Southern Ag BT are readily available online and in most garden stores and nurseries.
Try to be intentional in your application of insecticides, avoiding beneficial insects that may actually be playing an important role in protecting your plants from cabbage worms and other herbivores by acting as predators.
4. Natural Predators Will Feed On Cabbage Worms
There are a lot of reasons to encourage natural biodiversity in your garden, but supporting naturally occurring predator insects is a particularly helpful tool to have in your toolbox.
Stink bugs, ladybugs, ambush bugs, wasps, and birds are all common garden predators that will either eat or parasitize cabbage moths, especially larvae or juvenile caterpillars.
The best way to create biodiversity that will attract a rich variety of birds, insects, and arachnids to your garden is simply to plant a wide variety of plants, particularly pollen-rich flowers.
The other benefit of creating this diversity in your landscape is that it reduces the impact on your garden if you do have a bad pest infestation or if disease or fungus targets a particular plant or plant family.
When your landscape lacks biodiversity, this type of infestation can devastate the whole garden, but with variety, you will always have other plants that are more resilient or completely unaffected by the disease or pest.
5. Choose Pest-Resistant Plant Varieties
Because cabbage worms have been present in the U.S. for hundreds of years, horticulturalists have bred resistant varieties of Brassica plants and identified which types have the best natural resistance. Many nurseries and garden stores will have pest-resistant plant varieties available.
The University of Florida specifies Chinese cabbage, turnip, mustard, rutabaga, and kale as Brassica species that are less likely to be targeted by cabbage worms than others on this list.
Even though these species might prove to have higher resistance against cabbage worms, they may still be impacted by them, especially if more vulnerable species are not available.
Intersperse resistant varieties of Brassicas with a wide variety of other plants to create an environment that does not support large populations of cabbage worms.
6. Neem Oil And Other Insecticides Can Be Effective Control
Another all-around effective insecticide to have in any gardener’s arsenal is Captain Jack’s Neem Oil or other spray-on neem oil products. Neem oil coats your plants in an oily film that covers pests that quickly dehydrates them or prevents the exchange of oxygen.
Neem oil is also a great fungicide and protects plants from disease, which is what makes it an all-around great product to use for most plant issues.
Neem oil degrades quickly, so you will need to apply it liberally and often, at least every couple of weeks as long as it’s not rainy.
That’s A wrap!
We’ve covered a lot of information quickly, so let’s do a quick recap to remind you of what we’ve learned.
Cabbage worms are actually caterpillars, the larval form of the mature cabbage butterfly, which are small and white with black spots on their wings.
Cabbage worms, as their names suggest, feed mainly on cabbage and other species in the Brassica family. Cabbage worms mainly eat the following vegetables:
- Mustard plants
- Collard greens
- Radish greens
- Turnip greens
- Brussel sprouts
- Tomato leaves
- Potato leaves
- Squash or watermelon leaves
Cabbage moths can do some serious damage if left unchecked, and you should definitely try to take control of their populations before they get out of control.
Bryant, A., Coudron, T., Brainard, D., Szendrei, Z.. (2014) Cover crop mulches influence biological control of the imported cabbageworm (Pieris rapae L., Lepidoptera: Pieridae) in cabbage. Biological Control. 73, 75-83.
Dickson, M.H. & Eckenrode, C.J. (1980) Breeding for Resistance in Cabbage and Cauliflower to Cabbage Looper, Imported Cabbageworm, and Diamondback Moth. Journal of the American Society of Horticultural Science. 105(6), 782-785.
Jaques, R.P., (1972) Control of the Cabbage looper and the Imported Cabbage worm by Viruses and Bacteria. Journal of Economic Entomology. 65(3), 757–760.
Twinn, C.R. (1923) Studies in the Life-history, Bionomics, and Control of the Cabbage Worm in Ontario. 54th Annual Report of the Entomological Society of Ontario. 82-86.