Imported Cabbageworm

Pieris rapae

0 host plants

Last updated

Data Maturity Baseline

This profile contains verified pest data from extension databases. Regional field notes and expert review are in progress.

Quick Reference

Order
Lepidoptera
Type
larva (leaf-feeding caterpillar)
Host Plants
0
Peak Activity
April through October; continuous with overlapping generations
Damage Severity
moderate

Monitoring & Action

How to Monitor

Watch for white butterflies hovering around brassica plantings. Check undersides of leaves for single yellow-green eggs and green caterpillars. Frass pellets on leaves indicate active feeding.

When to Act

Treat when caterpillars are present and actively feeding on young plants. Established plants tolerate moderate feeding.

What Damage Looks Like

Caterpillars chew ragged, irregular holes through brassica leaves. Leave dark green frass pellets on leaves. Can defoliate young plants. Damage starts at outer leaves and works inward.

Cultural Controls

  • Floating row covers or screen cages prevent adult butterflies from laying eggs on crops
  • Hand-pick caterpillars from leaves; effective on small plantings
  • Remove and destroy pupae found on garden structures in fall and winter

Sources & References

Primary: WSU HortSense