Plant Problem Diagnostic
Harlequin Bug on Cabbage-Family Crops
The short answer
The harlequin bug is a shield-shaped bug, brightly colored black and yellow or black and red, that uses piercing-sucking mouthparts on cabbage-family crops like cabbage, kale, collards and mustard.
Its feeding leaves white spots called stipples, and heavily fed foliage turns brown and tattered while plants may wilt, become deformed, or die.
Handpick adults, nymphs and eggs and drop them into soapy water, and clean up garden debris to remove overwintering sites.
For added protection use floating row cover to exclude the pest, plant a trap crop, and treat hot spots with insecticidal soap, pyrethrum or neem oil if needed.
How to identify harlequin bugs and their eggs
Adults are shield-shaped, up to about 3/8 inch long, and brightly colored in black and yellow or black and red patterns.
The University of Maryland describes the distinctive eggs as tiny white barrels encircled by black bands with a black crescent on top, laid in small clusters arranged in rows of six on leaf undersides, a giveaway that separates this pest from other cabbage insects.
What they attack and the damage they cause
Primary hosts are cabbage-family members including broccoli, cauliflower, collards, kale and horseradish, with secondary hosts such as bean, tomato, squash and others.
Feeding produces white spots known as stipples; affected foliage browns and looks tattered, and plants may wilt, be deformed, or under severe infestation die.
Control without heavy spraying
- 1Handpick and destroy — Remove and destroy eggs, nymphs and adults by hand, dropping them into soapy water rather than squishing them.
- 2Sanitation — Remove garden debris to eliminate overwintering sites for the bugs.
- 3Exclude — Apply floating row cover over cabbage-family crops to keep the pest off the plants.
- 4Trap crop — Grow cleome as a trap crop, since harlequin bugs prefer it, to draw pressure away from the main crop.
When to use a product
If handpicking and cultural steps are not enough, the University of Maryland lists spraying with insecticidal soap alone or in combination with pyrethrum, or using neem oil.
Treat the infested plants and undersides of leaves where the bugs and eggs concentrate rather than blanket-spraying the whole bed.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Maryland Extension — Harlequin Bug on Vegetables — Verifies shield-shaped body up to 3/8 inch, black and yellow or black and red coloring; cabbage-family hosts; white stipple spots and tattered browning foliage with wilting, deformity and death; the white-barrel eggs banded in black with a black crescent laid in rows of six on leaf undersides; and management by removing debris, destroying eggs/nymphs/adults, floating row cover, cleome trap crop, and insecticidal soap with pyrethrum or neem oil.