If something is devouring your cabbage, broccoli or cauliflower plants, you have good reason to suspect the cabbage looper worm (Trichoplusia ni).
These caterpillars are lepidopteran insects and one of the main insect pests affecting cole crops.
The term, Lepidoptera, refers to one of the largest orders of insects, butterflies, and moths.
Typical Lepidoptera larvae are caterpillars armed with powerful chewing mouthparts designed for gobbling up vegetation.
Cabbage loopers are insect pests specializing in decimating cole crops (aka: crucifers, cruciferous veggies or brassica). These host plants are cool weather plants and members of the mustard family. They include:
- Chinese cabbage
- Brussels sprouts
- Broccoli raab
In addition to caterpillars eating leaves and laying waste to cole crops, cabbage loopers will happily destroy your:
To minimize damage, choose tolerant varieties of cole crops. Some examples include these three green cabbage varieties:
- Savoy Chieftain
- Green Winter
In general, cabbage loopers seem not to prefer red cabbage. [source]
What Do Cabbage Loopers Look Like?
Fully grown looper caterpillars are quite large and about one-and-a-half inches long.
They are a bright, light green with four thin, white, horizontal lines – two on the back and one on each side.
These caterpillars get their name from the way they move. When they ambulate along, they arch their bodies like an inchworm.
The cabbage looper’s odd gait occurs because these caterpillars have only three pairs of legs, as opposed to the five pairs most caterpillars have.
Although this strange locomotion causes these pests to look like inchworms (Geometridae family), the two types of insects are not related.
Cabbage loopers are related to corn earworms, pesky armyworms, and cutworms, which are all pests belonging to the noctuid moth family.
Adult looper moths are a nondescript grayish/brown with brown mottling and a distinctive “8” or “Y” shaped marking on the forewings.
They have a wingspan of approximately an inch-and-a-half and can be found flying about after dark.
What Does Cabbage Looper Damage Look Like?
These green caterpillars eat up the vegetation between the midribs and large veins of cole crop leaves.
They produce large, ragged holes in the upper surface of leaves near the midribs.
If feeding is excessive, crop growth will be stunted. This is especially notable on cauliflower and cabbage heads.
The cabbageworm may also damage buds as they emerge on young cabbage plants, which completely prevents head development.
They may also bore into small cabbage heads early in development. This stunts the growth of the produce.
In addition to shredding plant leaves, cabbage looper caterpillars also produce great quantities of droppings (frass) which may contaminate the plants and their produce.
Loopers can also damage root crops, but this damage is typically insignificant.
How Can You Find Cabbage Loopers?
Inspect your yard and garden regularly for signs for this insect pest and others.
Check the tops and undersides of leaves for eggs and larvae.
Look for damage to leaves and frass on plants and on the ground beneath plants.
Keep a close eye on seed beds as these are prime targets for these green caterpillars. They love to prey on tender young shoots.
When cabbage loopers attack a mature, healthy plant it is possible for the plant to survive. They will completely lay waste to seedlings, though.
The Life Cycle Of The Cabbage Looper
Some cabbage looper moths overwinter in the southern United States and migrate north in the summertime.
Others overwinter in plant debris in areas where the winter is too cold for them to be active but not so cold that it kills them.
Like most insects, the moths reproduce during the warm months of summer, laying their eggs on the undersides of leaves throughout the month of July.
After the eggs hatch, it takes about a month for the larvae to pupate.
The pupal stage lasts for a couple of weeks and then moths emerge, mate and lay a second batch of eggs.
In the northern United States, you can expect two generations of cabbage loopers during the growing season.
In the extended growing season of the warmer, southern states, it is possible for them to complete four reproductive cycles annually.
How To Get Rid Of Cabbage Loopers and Kill Caterpillars
You must get rid of these pests the minute you see them.
Use a good Integrated Pest Management (IPM) control system to attack them on numerous fronts. Here are some smart practices to help keep these and all sorts of caterpillar pests at bay.
#1 – Inspect New Transplants
Be very careful never to introduce an infested plant to your garden. Inspect all transplants carefully and quarantine them for a couple of weeks before setting them out in your garden.
#2 – Scout For Cabbage Looper Eggs
Cabbage looper eggs are very small and pale green. You will find them in clusters on the undersides of leaves. Learn to recognize the eggs and remove them by hand whenever you see them. Be careful not to remove the eggs of beneficial predatory insects.
#3 – Use Chickens
Chickens make a good line of attack against cabbage loopers.
If you keep a flock, allowing them into your garden periodically can be a good way of getting rid of these pests and turning them into something useful (eggs and/or meat).
#4 – Floating Row Covers
Use floating row covers over your cole crops to block entrance to these pesky caterpillars. Use netting to block access to cabbage moths.
#5 – Sprinkle Diatomaceous Earth
Sprinkle food grade diatomaceous earth liberally around and on plants where cabbage loopers are expected or have been seen. More on using food grade diatomaceous earth.
#6 – Hand-Pick
Hand pick the critters as you see them. If there are only a few, simply pick them off and drop them into a bucket of soapy water as you walk through your garden.
#7 – Clean Leaf Litter
Clean up leaf litter in the fall. Don’t give the pupae and moths a cozy place to overwinter.
#8 – Control Weeds
Keep your weeds under control because these pests can also overwinter in weeds. Be sure to cut weeds such as:
- Shepherd’s purse
- Wild mustard
- Pepper grass
… down to the ground in autumn to do away with pest hiding places.
#9 – Dust With Cornmeal
Dust your plant leaves with cornmeal. When caterpillars eat it, it swells in their stomachs and kills them.
#10 – Use Companion Planting
Use a companion planting method. Some plants repel pests. Good examples include very aromatic herbs, such as mint and thyme.
Planting these herbs among your cole crops can help keep cabbage looper moths away.
#11 – Make All-Natural Organic Pests Sprays
Make your own insect repellent spray using natural products such as Neem oil, cayenne pepper and garlic. To see our recipes below:
#12 – Apply Insecticidal Sprays
Use insecticidal sprays sparingly and always opt for natural controls whenever possible.
Cabbage loopers are susceptible to a number of different insecticides, including:
- Carbaryl (Sevin)
Of these, spinosad is the best option and least detrimental to the natural balance of your garden.
If you use any of these products, use it sparingly and in conjunction with other methods. Be sure to follow all packaging directions closely.
#13 – Introduce Beneficial Insects
Engage the assistance of beneficial insects.
Natural enemies and predators (even bug juice spray insecticide) such as ground beetles, parasitic wasps, praying mantis and garden spiders can be very helpful in getting rid of the cabbage looper moth and lots of other pests.
Lizards (e.g. geckos) and birds are also quite fond of these plump, juicy invaders.
#14 – Apply Insecticidal Soap Sprays
Insecticidal soap is a mild deterrent that can be effective against cabbage loopers without doing much harm to your beneficial fauna. [source]
You can purchase specially produced insecticidal soap or make a simple insecticidal soap spray using a little plain dish soap or an organic liquid castile soap if you prefer.
Insecticidal soap can kill off lots of different sorts of pests. Spray it directly onto pests such as aphids, small caterpillars and other small, soft-bodied bugs to kill them on contact.
#15 – Use Natural Bacillus Thuringiensis
Bacillus thuringiensis (Bt) is an excellent deterrent against all sorts of caterpillars. If you are asking the question – “How to get rid of caterpillars naturally?” Check out Bt.
Bt works by causing their intestines to swell and explode. Be sure to follow all packaging instructions. It’s best to apply the product early in the season to catch the caterpillars while they are very small.
Apply it carefully, sparingly and only to plants where you have seen cabbage loopers.
You don’t want to also kill off harmless moth and butterfly caterpillars.
This natural bacterium is readily available at your local garden center or online in both a liquid and powder form.
Good Cabbage Looper Control Is Effective Against All Caterpillars
When you know how to control cabbage loopers, you know how to control all kinds of caterpillars.
If the caterpillars you see do not quite match the cabbage looper description but are laying waste to your cole crops and other plants, these tips can still be useful.
You may be dealing with some other sort of brassica-loving pests such as garden webworms, diamondback moth larvae or imported cabbage worms. It matters not.
They are very similar and will succumb to the same weaponry needed to subdue cabbage loopers.