Diamondback Moth

How to identify it

• Mature caterpillars are small, about 1/3 inch, green-yellow with black hairs, and pointed at both ends.^[1]
• Two prolegs at the rear form a distinctive V.^[1]
• They pupate in loose white cocoons attached to leaves or stems.^[1]

Where it lives

It may be found year round in California and is often abundant in spring and early summer, rising again in fall.^[1]

US map: public records from 50 states since 1990 (GBIF). View the map

Biology and life cycle

Adults lay tiny eggs singly or in twos and threes under leaves.^[1]

Larvae mature in about 10 to 14 days, and there are four to six generations a year.^[1]

Damage and signs

• Larvae chew small holes, mostly on undersides of outer leaves, which matters mainly on cabbage wrapper leaves.^[1]
• Chewed growing points stunt young plants, and some larvae bore into broccoli or cauliflower heads.^[1]

Health risk

It feeds on cole crops; UC IPM mentions no risk to people.^[1]

Control

Sanitation

Destroy crop culls and mustard-type weeds several weeks before planting.^[1]

Biological control

Natural enemies often control it; Diadegma insularis wasps parasitize larvae, and Trichogramma pretiosum may attack eggs.^[1]

Bacillus thuringiensis or spinosad sprays are very effective.^[1]

Common questions

What are the tiny green caterpillars that wriggle when touched on my broccoli?

Likely diamondback moth larvae, which are small, pointed at both ends and have a V of rear prolegs.^[1]

Do I need to spray?

Often not; older plants usually aren't seriously harmed and natural enemies are effective.^[1]

Sources

1. University of California Statewide IPM Program, “Diamondback Moth (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/diabackmth.html (accessed 2026-10-06)
2. iNaturalist, “Plutella xylostella taxon page (order and family).” www.inaturalist.org/taxa/911325 (accessed 2026-10-06)