Cabbage Looper

• Irregular ragged holes in cabbage, kale, or broccoli leaves — often starting on outer leaves then moving inward
• Green caterpillar arching its back in a looping motion as it crawls (the distinctive identifying behavior)
• Frass (dark green pellets) on leaf surfaces and caught in leaf folds
• Leaves eaten down to the midrib on severe infestations
• Small white eggs, ribbed and dome-shaped, on the upper surface of leaves
• Damage concentrated on mid-canopy leaves, not just the outermost or innermost

Adults are brownish moths with a small silver figure-eight marking on each forewing. They migrate northward each season rather than overwintering locally in cold climates, arriving mid-summer when populations build. Females lay eggs singly on leaf surfaces; larvae hatch within a week and feed for 2–4 weeks before pupating. Multiple overlapping generations can occur in a single season, so pressure tends to intensify from midsummer onward. The looper is often confused with the imported cabbageworm (Pieris rapae), which is a distinctly different species — the imported cabbageworm is velvety with a faint yellow stripe and walks without arching.

1. 01Check leaf undersides and inner canopy weekly from midsummer onward — early detection keeps populations manageable
2. 02Hand-pick caterpillars and eggs when populations are low; drop them in soapy water
3. 03Cover plants with floating row cover before moths arrive to prevent egg-laying entirely
4. 04Apply Bacillus thuringiensis var. kurstaki (Bt) spray to foliage when caterpillars are small — Bt is specific to caterpillars and breaks down quickly; reapply after rain
5. 05Spinosad (a soil microbe-derived insecticide) is effective on larger larvae that have passed the Bt window
6. 06Encourage parasitic wasps by leaving some flowering herbs such as dill or fennel nearby — Trichogramma wasps parasitize looper eggs

If damage is severe despite Bt applications and you're unsure whether you're dealing with loopers, imported cabbageworms, or both simultaneously, an extension diagnostic lab can ID the caterpillar from a sample and advise on timing.

• Cabbage Looper — Vegetable IPM— UC ANR Integrated Pest Management
• Caterpillar Pests of Cole Crops— University of Minnesota Extension