Cabbage worms and loopers: how to spot it and what to do

Cabbage worms and loopers

Insect or pest Pieris rapae, Trichoplusia ni · also called imported cabbageworm, cabbage looper, cabbage white butterfly

Holes or chewed leaves Damaged fruit, pods, or ears Bugs I can see

A green cabbage worm on a chewed leaf — Photo: 螯蝦, iNaturalist (CC0)

A velvety green cabbage worm on a leaf with ragged holes — Photo: Chris Gannaway, iNaturalist (CC0)

How to spot it

Velvety green caterpillars about 1 inch long. Cabbage worms have a faint yellow line down the back; loopers are paler and arch into a loop as they crawl. The white butterflies with black spots fluttering around your cabbage lay the eggs.

What it does

They chew ragged holes in leaves and bore into heads of cabbage and broccoli, leaving green droppings behind.

What to do now

Pick off caterpillars, and rub off the tiny yellow eggs under leaves.
Spray Bt (Bacillus thuringiensis kurstaki) or spinosad on the leaves; Bt only harms caterpillars.

Keep it away next time

Cover cabbage-family crops with row cover from planting on. They don't need bees, so it can stay on.
Grow dill, thyme, and alyssum nearby for the wasps that attack caterpillars.
Check plants weekly from spring on.

Helpful supplies

Bt caterpillar spray Insect netting Spinosad spray

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Plants it affects

Every plant in the cabbage family (brassicas).

Lettuce

Not sure? Your county extension office can identify it from a photo or sample, often for free.