How to Get Rid of Cabbage Worms

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Learn how to keep pesky cabbage worms from destroying your garden’s cabbage, broccoli, Brussels sprouts, and cauliflower.

Cabbage worms can pose a real threat to cruciferous vegetables in the garden. These velvety green caterpillars nibble at leaves and vegetables and can even contaminate crops with their fecal matter. If left untreated, they can nearly decimate the cabbage, broccoli, cauliflower, and other cruciferous crops in a garden, leaving behind only veins and stems.

Knowing how to get rid of cabbage worms is essential in preventing this garden pest from wreaking havoc and wiping out plants.

What Are Cabbage Worms?

Cabbage worms, also known as imported cabbage worms, are a type of caterpillar. These pests feed on plants from the Brassicaceae family, which includes cruciferous vegetables like broccoli, Brussels sprouts, cabbage, collard greens, kale, rutabaga, and turnips.

Once cabbage worm larvae undergo metamorphosis, the butterflies are referred to as small whites, cabbage whites, or cabbage moths. Female adult butterflies lay their eggs on the underside of leaves. Since baby caterpillars quickly emerge to feed on the leaves of these plants, adult cabbage moths also pose a threat to the health of cruciferous plants in the garden.

Identifying Cabbage Worms

Closeup of cabbage worm crawling on lettuce — Photo: istockphoto.com

Cabbage worms are light-green with a faint yellow stripe running down their back and additional yellow stripes crossing their body. They have velvety soft hairs. Once cabbage worms first hatch from their eggs, they are very tiny, while full-grown cabbage worms will be about 1 inch long.

Life Stages

There are four stages in the cabbage worm life cycle: egg, larva, pupa, adult. Depending on the weather, it can take between 3 and 6 weeks for the cabbage worm to go through all four stages of the life cycle.

Egg: Adult cabbage white butterflies lay their eggs on the underside of leaves of plants in the Brassicaceae family. Cabbage worm eggs are very small—just ½ to 1 millimeter (mm) long. The eggs are pale white immediately after being laid but will change to a yellowish color before the larvae hatch.
Larva: The larval stage lasts for about 15 days. During this time, the caterpillars go through five instar stages as they molt their exoskeleton and grow. The caterpillars that emerge from the eggs are only about 3 mm long, or a little under ⅛ inch. By the end of the fifth instar, they will be about 25 mm, or 1 inch, long. During all but the first instar stage, the larvae will have a characteristic yellow line running down the center of their backs, though it may not be a solid line in the earlier instars.
Pupa: Cabbage worms normally form their pupae, or chrysalises, on plants. While the chrysalides may vary in color, they are typically green, yellow, gray, or speckled brown. This stage in the life cycle lasts for about 11 days, though it can be significantly longer if in the overwintering stage.
Adult: Adult butterflies have pale-yellow wings with very faint black spots. Their wingspan is between 4½ and 6½ centimeters (about 1¾ to 2½ inches). The females’ bodies are covered in white hair, and the males’ bodies are covered with a darker color. Female butterflies can produce as many as 300 to 400 eggs during their 3-week lifespan.

Plant Damage

Cabbage worms can cause significant damage to garden plants. As mentioned above, these pests feed on cabbage, broccoli, kale, collard greens, cauliflower, Brussels sprouts, and other Brassicaceae family members. The first evidence of cabbage worms in the garden will likely be the appearance of uniform holes between the veins in the leaves of these plants.

If a garden is facing a large cabbage worm infestation, the plant damage can be more severe. The worms may eat all of a plants’ leaves, leaving behind just the veins and stems. Beyond leaf damage, cabbage worm feces can contaminate a plant’s vegetable growth.