InsectUpdated Apr 2026

Harlequin Bug

Murgantia histrionica

White blotches that turn brown on brassica leaves, caused by brightly patterned orange-and-black stink bugs injecting toxic saliva.

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Symptoms

  • White or yellow blotches on brassica leaves that turn brown and papery as the feeding site collapses
  • Wilting of young plants that does not recover with watering — caused by toxic saliva injected during feeding
  • Shiny black and orange (or red) shield-shaped bugs, about 3/8 inch long, visible on stems and leaf undersides
  • Barrel-shaped eggs in distinctive double rows of 12, white with black rings, on leaf undersides
  • Stunted growth on broccoli and cabbage transplants attacked early in the season
  • Both nymphs and adults cause damage; nymphs share the vivid patterning of adults but are smaller and rounder
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Life cycle

Harlequin bugs are true bugs (Hemiptera) and overwinter as adults in plant debris and weedy patches near gardens, especially in the southern and mid-Atlantic United States. They emerge in early spring and move to brassica hosts quickly. Females lay two egg masses per cluster, each in a neat double row. There are two to three generations per year in warmer climates. The bug is difficult to control once established because both adults and nymphs move readily between plants. Host-plant remnants left in the garden over winter are a primary source of next-season pressure.

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Management

  1. 01Remove and dispose of all brassica crop debris promptly after harvest — do not compost it; this is the single most effective step
  2. 02Hand-pick adults, nymphs, and egg masses in early morning when bugs are sluggish; drop into soapy water
  3. 03Plant a trap crop of mustard greens at the garden perimeter; monitor it closely and destroy infested plants before bugs move to main crops
  4. 04Kaolin clay applied as a particle barrier can deter feeding when reapplied consistently after rain
  5. 05Neem oil or insecticidal soap can suppress nymphs but is less effective on adults with their waxy cuticle
  6. 06Where populations are severe, pyrethrin-based insecticides labeled for stink bugs are a last resort — apply in the evening to reduce impact on pollinators
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When to call extension

If harlequin bugs are consistently destroying transplants in early spring before you can intervene, a local extension office can advise on timing-specific management and whether trap-cropping is practical at your scale.

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Sources

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