Cabbage Worms And Cabbage Loopers

If you are seeing holes in cabbage leaves or frass (dark green droppings) collecting in the center of plants, cabbage worms or loopers are likely the cause.

What They Look Like
Cabbage worms are velvety green caterpillars that move slowly and blend into leaves.
Cabbage loopers are smooth, light green caterpillars that move in a distinctive looping or inchworm motion.
Both are often found on the undersides of leaves and can be difficult to spot until damage appears.
White butterflies hovering around brassicas are usually a sign that cabbage worms are present or about to be.

Damage Signs
Large irregular holes in leaves
Leaves may appear skeletonized, with only veins remaining
Dark green droppings (frass) visible on leaves or in plant centers
Damage often begins on outer leaves and works inward
Cabbage heads and broccoli florets may become contaminated

Plants Affected
Cabbage
Broccoli
Cauliflower
Kale
Collards
Brussels sprouts
Lettuce and leafy greens

Fast Control (Start Here)
Inspect plants daily, especially the undersides of leaves
Handpick caterpillars as soon as they are seen
Crush eggs before they hatch
Act early before caterpillars move deep into plant centers

Additional Control Options
Apply BT (Bacillus thuringiensis) when caterpillars are small and feeding
Spray thoroughly, including undersides of leaves
Reapply as needed to stay ahead of new hatch cycles
Use spinosad only if needed and with caution around beneficial insects

Prevention
Cover plants early with row covers to prevent egg laying
Check plants frequently once butterflies or moths are active
Encourage beneficial insects such as parasitic wasps
Clean up plant debris at the end of the season to reduce overwintering pests

Notes for Gardeners
White butterflies are a warning sign, not decoration
Damage often appears before you ever see the caterpillars
Frass is often the first clue something is wrong
Early action prevents pests from hiding deep inside heads where they are harder to reach