If you’ve ever grown cabbage, you’ve probably had your own battles with cabbage worms. These small worms can do a lot of damage and need to be dealt with as soon as you spot them in your garden. Here are some natural, organic ways to control cabbage worms in your garden.
How to Identify Cabbage Worms
The cabbage family is host to many pests that people refer to as cabbage worms. This includes the actual larvae of a cabbage white butterfly (Pieris rapae), cabbage loopers (Trichoplusia ni), zebra caterpillars (Melanchra picta), and the larvae of the diamondback moth (Plutella xylostella).
An actual cabbageworm is the larvae of the cabbage white butterfly. If you see the white butterflies with black markings flying around your garden, they are likely laying teeny, tiny eggs all over your cabbage plants. These worms are not to be confused with the cabbage looper but do look similar. Cabbage worms are fuzzy and green with subtle yellow markings on them.
A cabbage looper is more of a yellow-green and does not have legs in the center, so instead of walking straight ahead, they inch forward by “looping”.
While we get our fair share of cabbage whites, the main pest problem on our cabbage crops is zebra caterpillars. These guys are black, white, and green. They eventually turn into an American noctuid moth.
And lastly, the diamondback moth caterpillar. This is a small, green caterpillar with white and black dots on it.
Identifying If You Have Cabbage Worms
All of the above pests feed on cabbages and other cabbage family crops and can be referred to as cabbage worms. They are all, however, very good at camouflaging and their eggs are very, very small and difficult to spot.
The eggs, while tiny, are typically laid on the outer leaves on the underside. The worms will likely be found in the same areas. On the underside of leaves, hiding toward the middle of the plant, etc. They are generally whitish or yellowish in color and have tiny, oblong eggs. You will find them singly laid, not in groups. Groups of a similar colored, oblong egg are ladybug eggs.
Once they become a problem, you’ll find holes eaten through your plants and an infestation can easily decimate a crop to leave only the thick stems of the plant left behind.
If you only see a hole or two, you don’t have a major problem, but if your plant has several holes in it, you already have a major issue with caterpillars or cabbage worms.
The easiest way to identify and combat a problem in the early stages is you’ll see frass, or fecal matter, on your plant. It looks like small, yellow, brown, or greenish spots all over the place, usually in groups. If you routinely check your crops, you’re going to see the frass before you find any other signs of cabbage worms.
How to get rid of cabbage worms
If you happen to see cabbage worms, their eggs, or their fecal matter, it’s time to get them under control… now. Leaving them to their own devices is a sure fire way to have very little crop left.
Thankfully there are several natural and organic ways to get rid of cabbage worms in the garden. Let’s discuss:
Remove Cabbage Worms and Eggs By Hand
Depending on how grossed out by insects you are, this can be an easy method to get rid of the creepy crawlies. You can even get your kids involved (I know mine absolutely love to pull the caterpillars off of our plants).
As for the eggs, as mentioned above, they are tiny, oblong whitish or yellowish eggs. However, you should only see single eggs. If you see a group of tiny, oblong white or yellow eggs, laid together it is more likely ladybug eggs and those you don’t want to pull off or kill as they are a natural enemy of what you’re trying to combat.
You can either take the caterpillars and put them in a bucket of soapy water or you can simply pull them off, put them in a small container and feed them to your backyard chickens when you’re finished.
Cornmeal has some interesting uses in the garden, for sure, and killing off cabbage worms is one of those. You can simply wet down your plants with water and generously sprinkle some cornmeal on them. The worms will eat the cornmeal and it will cause them to swell and die.
Make a Homemade Spray
Mix together 1/4 cup vinegar to 3/4 cups water, and 1 teaspoon of soap. The soap will help it stick to the leaves. Spray on tops and bottoms of leaves, sparingly. To use this spray, you’ll want to make sure that you don’t saturate the leaves and that your plants aren’t young small seedlings. Also, I recommend testing it in a small area of the plant (just in case) and spraying it in the evenings, not in the heat of the day (which can cause your plants to bake in the sun).
I’ve used this spray for several years and had no issues with it at all, but I spray it sparingly on mature plants in the evenings. It does contain vinegar, which is a natural herbicide (and great for killing weeds), but I’ve never had a problem with this diluted spray.
Spray With Bt
Bacillus thuringiensis (or Bt for short) is an organic pesticide that can be utilized to kill off a variety of pests in the garden. This microbe is found naturally occurring in the soil and has been used in organic gardening and farming for many years.
Bt is only toxic to the larvae of butterflies and moths and is not toxic to birds or other mammals, making it a great, organic pesticide to use to control cabbage worms and other pests in the garden.
You can spray Bt on your plants every two weeks or so to kill off any infestation you may have. If any worms remain, they will be minimal and you can easily pick them off or wash them out. It is considered safe for human consumption so it can be sprayed as soon as the day of harvest with no ill effects.
Try Spraying Plants or Worms with Neem Oil
Neem oil is a wonderful, natural pesticide that can help kill off caterpillars and other soft-bodied pests in the garden (like aphids). It can be sprayed directly on the cabbage worms to kill them off.
Neem oil can also be sprayed onto the plants to help repel the moths and butterflies from laying eggs. However, like some of the other preventatives I’ve listed below, neem oil isn’t likely to completely solve your problem and is best used in conjunction with other methods.
Use ducks to eat the worms
Ducks, chickens, and even songbirds will eat the worms (and butterflies) when given the opportunity. So, invite them in.
Chickens may very well eat your cabbage, so I highly recommend ducks (which won’t as long as the plant is mature). They enjoy cabbage worms and will definitely eat them if given enough opportunity.
I love the idea of symbiosis. Allowing the natural world to do what the natural world does. So, invite your ducks, or invite some songbirds into your garden and let them do their thing.
Preventing Cabbage Worms
An ounce of prevention is worth a pound of cure and the same stands for keeping cabbage worms from ever becoming a problem. These methods won’t work if you already have a problem, but they can help keep them from ever becoming a problem. Let’s discuss them.
Invite beneficial insects into your garden.
Garden pests of all kinds have enemies and lots of them. So, invite all of their natural enemies into your garden. Lady beetles, Trichogramma wasps, yellow jackets, spiders, and the green lacewing are all enemies of cabbage worms.
The most popular of the natural enemies are the Trichogramma wasps (or parasitic wasps), which you can actually purchase. Unlike the large, annoying stinging wasps we all envision when we hear the word wasp, these are small and harmless to humans. You will often find their eggs on the backs of caterpillars, particularly tomato hornworms.
However, be forewarned that these parasitic wasps will kill all caterpillars, so if you invite or raise other butterflies such as monarchs, you may want to hold off on purchasing them.
Spray cabbage crops with tansy oil
Like the neem oil mentioned above, tansy oil is a great, natural, organic way to keep cabbage worms at bay. You can spray your crops with tansy oil to deter them from laying eggs on your cabbage. While not 100%, it will help to break the cycle.
Utilize Companion Planting
Companion planting is every gardener’s best friend. There are a few plants that can help repel cabbage moths and others from being interested in making your plants home for their young.
Marigolds, thyme, dill, and other cabbage companion plants can help deter the moths from being interested in laying their eggs. But, none of these will completely repel the butterflies. I have marigolds planted all around our cabbages and we still have worms.
Also, instead of utilizing the oil you could plant tansy nearby just be careful, this particular plant spreads like wildfire.
Another idea is to plant mustard near your cabbage plants. Mustard will attract the cabbage butterflies and can be an excellent trap to catch the problem. Simply remove the plant when you’re finished.
Use floating row covers
If you already have a lot of worms on your cabbages, floating row covers won’t get rid of them. However, they can be placed in order to keep more eggs from being laid.
I find row covers work best on raised beds than they do in traditional row gardens, but they can be used even on individual plants. These can be put in place not only to keep insects off but also to keep the birds from eating your crops.
Row covers can be left on all the time as they still allow sunlight in and they are easily pulled out of the way when you need to fertilize, harvest or simply to check on your crops.
Use Red or Purple Cabbage Varieties
While this won’t really repel or prevent cabbage worms, it will make them immensely easier to see. We like to interplant red and purple varieties with our green cabbages. Not only to help keep cabbage worms under control but simply because… who doesn’t like variety?
There are other ways to repel cabbage worms, but these are the best ways we’ve found to keep them at bay. If you put row covers on as soon as you plant, you will likely never gain a problem from them. If row covers aren’t possible, or just aren’t your thing, just make sure you have some of the natural enemies to eat them up and pick the rest off by hand.