Plant Problem Diagnostic
Cabbage Worms in the Garden
The short answer
The imported cabbageworm is a velvety green caterpillar, up to about an inch long, that chews holes in cabbage, broccoli, kale, and other cole crops; the adult is the familiar white butterfly with black wing spots. The best prevention is floating row cover placed at transplanting to keep the butterflies from laying eggs.
Where crops are uncovered, hand-pick caterpillars into soapy water and check leaf undersides for eggs. For heavier pressure, the least-toxic microbial category Bt (Bacillus thuringiensis) targets young caterpillars, and natural predators and parasitoids also help keep numbers down.
How to identify it
Caterpillars are velvety green with a faint yellow stripe down the back, growing to about an inch, and blend into cole-crop leaves. Adults are white butterflies with black spots near the forewing tips. Eggs are yellow and oblong, laid singly on leaves. Damage is ragged holes and dark droppings, often near the center of heads.
- Velvety green caterpillar with faint yellow stripe
- White butterfly with black wing spots (adult)
- Yellow oblong eggs on leaves
- Ragged holes and droppings in cole crops
IPM least-toxic management
- 1Exclude with row covers — Place lightweight floating row cover over cole crops at seeding or transplanting to stop the adult butterflies from laying eggs.
- 2Scout and hand-pick — Check leaf undersides for eggs and pick caterpillars into a pail of soapy water.
- 3Use Bt if needed — For active caterpillars, the Bt (Bacillus thuringiensis) category can be applied when small worms are found, targeting caterpillars specifically.
- 4Conserve natural enemies — Predators like paper wasps and lady beetles and various parasitoid wasps help keep caterpillar populations low.
When to escalate
If damage continues despite covers, hand-picking, and Bt, additional options exist. For product options consult your county Extension and always follow the label.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Caterpillars on cole crops — Imported cabbageworm is a velvety green caterpillar from a white butterfly; floating row covers exclude egg-laying adults, hand-picking and Bt manage caterpillars, and natural enemies help.