The imported cabbage worm is the larval stage of the cabbage butterfly. The adult butterfly has white wings, with black tips and spots on the forewings. Wingspan is about 1-1/2". Eggs are laid in the spring on the leaves of host plants, which include cole crops such as broccoli and cabbage, as well as radish, turnip, and nasturtiums. The caterpillars are green with faint yellow stripes along the back and sides. They feed on the leaves, chewing irregular holes in the leaf tissues. Mature caterpillars are about 1" long and may also feed in the center of cabbage heads. Black pellets of frass (excrement) are often present on the leaves. The caterpillar pupates in a pale green chrysalis which may be attached to any convenient object in the garden. Three to five generations may occur in a single season.

Management Options

Non-Chemical Management

Cover crops with floating row covers or screen cages to prevent egg-laying by adult butterflies.
Hand-pick any caterpillars found on leaves.
Pick and destroy any pupae found.
Natural enemies of caterpillars include predacious beetles, parasitic wasps, and birds. Avoid use of broad-spectrum insecticides when possible to conserve beneficial insects.
Remove debris which may shelter pupae.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Use product according to label instructions. Read the product label for timing between last application and harvest. Apply in spring about 10 days after flights of mating pairs are observed. Use a spreader-sticker with liquid Bt formulations.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
Active ingredient: spinosad (spinosyn A+D) | EPA reg no: 4-472
Bonide Thuricide BT Conc
Active ingredient: Bacillus thuringiensis subsp. kurstaki | EPA reg no: 4-226
Bug Buster-O [Organic]
Active ingredient: pyrethrins | EPA reg no: 1021-1771-54705
ferti-lome Dipel Dust
Active ingredient: Bacillus thuringiensis subsp. kurstaki | EPA reg no: 7401-290
Safer Brand Caterpillar Killer for Trees, Shrubs & Vegetables Conc II [Organic]
Active ingredient: Bacillus thuringiensis subsp. kurstaki | EPA reg no: 70051-106-42697
Safer Brand Caterpillar Killer/Trees, Shrubs, & Vegetables Conc
Active ingredient: Bacillus thuringiensis subsp. kurstaki | EPA reg no: 42697-23
This list may not include all products registered for this use.

Images

+ Show larger images


Caption: Imported cabbage worm and damage on cabbage Photo by: A.L. Antonelli
Caption: Imported cabbage worm adult Photo by: A.L. Antonelli

WSU Extension

Hortsense