Here are tips on how to identify, control, and get rid of cabbage worms.
What are Cabbage Worms?
Cabbage worms are the same pest as “imported cabbageworms.” The adult butterflies are sometimes called cabbage whites or small whites. The Latin name is Pieris rapae, or Artogeia rapae.
This is a common pest for cabbage, kale, cauliflower, broccoli, and other members of the cabbage vegetable family. Do not be overly concerned if you see a hole in a leaf; plants can withstand much leaf loss without consequence. It is during seedling establishment or early head formation that plants will incur true damage to their growth and yield.
How to Identify Cabbage Worms
Cabbage worms are velvety green larvae. They have a few faint yellow stripes. They are not to be confused with cabbage loopers, which are yellow-green caterpillars. Unlike cabbageworms, cabbage loopers raise and lower their bodies as they move because they have no middle legs. Cabbage worms become cabbage white butterflies, which are mostly white with a few black markings. Cabbage white butterflies might seem like a pretty addition to the garden, but they are probably laying eggs on the undersides of leaves.
Where you find cabbage worms and cabbage loopers, you also might find the eggs and larvae of the diamondback moth and the zebra caterpillar. The camouflage of these creatures is excellent, so you will often see the frass, or fecal matter, that they leave behind before you see them.
Photo Credit: Cabbageworm eggs like the one in this picture are absolutely tiny, so you might not see them before it’s too late.
Cabbage Worm Damage
Cabbage worms can happily eat away at the bases of cabbage, cauliflower, or the heads of broccoli without being noticed. They feed on foliage, and eventually they can leave plants only with stems and large veins. If left to their own devices, cabbage worms can devour your crops. Their fecal matter can also stain and contaminate the produce.
Photo Credit: Purdue University. Imported cabbageworms feed on the flesh of foliage and often hide on the undersides of leaves.
Control and Prevention
How to Get Rid of Cabbage Worms
Manually remove (handpick) the eggs if possible.
Yellow sticky traps will catch the adult butterflies, but may also catch beneficial insects.
Spraying with Bt (Bacillus thuringiensis var. kurstaki) every 1 to 2 weeks will also help control cabbage family pests. Sevin also is effective. And, the few pests that remain on the vegetables can be washed out after harvest using water and a small amount of detergent or other surfactant.
It is said that if you dampen cabbage leaves and sprinkle them with cornmeal, the caterpillars will eat the meal, swell, and die.
Old folk advice from The 1963 Old Farmer’s Almanac states: Years ago, people sprinkled rye flour over cabbage plants in the early morning. The flour dehydrated the cabbage worms. Give it a try!
Photo Credit: York College of Pennsylvania. It is hard to control cabbage worm damage, so it’s best to prevent them from coming to your garden in the first place.
Prevent Cabbage Worms
Cover your plants with row covers to deter the adult butterflies from laying eggs on the cabbages.
Trichogramma wasps (very tiny; they do not sting humans) parasitize the eggs of the imported cabbage worm; these beneficial insects are available by mailorder, although you’ll need to time their release appropriately—the mailorder company would be able to help you. Read more about beneficial insects.
Companion planting is a useful deterrent for many pests. Cabbage worms are repelled by thyme, so it would be a good idea to plant thyme near your susceptible plants. Cabbage worms are attracted to mustard plants, so planting mustard near more valuable plants can be a good trap for cabbage worms. Once they take over the mustard, you can destroy the plant.
Try planting red leafed varieties of cabbage. The cabbage worms won’t be able to camouflage, so they are less likely to choose these plants.