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How to identify it
- Adults are shield-shaped bugs, black or deep blue with vivid red, orange or yellow markings; NC State and New Mexico State put them at 1/4 to 3/8 inch long.[2][3][1]
- Eggs look like tiny white kegs with two black bands and a black circle or crescent on top, standing on end in a double row, usually 10 to 13 eggs (often two rows of six) under the leaves.[2][3][4]
- Nymphs are rounded and boldly patterned, cluster near their egg shells at first, and look like wingless adults as they grow.[2][1][4]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Bagrada bug | An invasive bug that is much smaller than the harlequin bug and has white markings the harlequin bug lacks.[1] |
| Consperse, Say and southern green stink bugs | Common garden stink bugs are gray-brown, green or bright green, without the harlequin bug's black body and bold red, orange or yellow pattern.[1] |
Where it lives
Native to Mexico and Central America; it was first reported in the United States in Texas in 1864 and in Kansas in 1870. It is a common pest in the southern states and is becoming more common farther north, as in Pennsylvania, though winter survival there is low.[3][4]
Biology and life cycle
Adults overwinter under crop residue and weed debris, then become active in spring and feed on wild and cultivated mustards.[2][3][1][4]
Females begin laying eggs about two weeks after emerging; in warm weather eggs hatch in 4 to 5 days, and in early spring they can take about 20.[2]
NC State says nymphs feed for 6 to 8 weeks and Kansas State 5 to 6 weeks before becoming adults; New Mexico State gives 30 to 50 days from egg to adult, depending on temperature.[2][4][3]
Adults release aggregation pheromones that draw them together, so they cluster on favored plants, which is what makes trap crops work.[3][4]
They hide on the undersides of leaves in the hottest part of summer days, since direct sun can kill them, and drop to the ground when disturbed.[4]
Damage and signs
- They pierce leaves, stems and veins and suck out the juices, leaving cloudy, white or yellow blotches that later turn yellow-brown.[2][1][4]
- Young plants can wilt, turn brown and die, while older plants are usually stunted or distorted.[2][3][4]
- Favorite hosts are mustard-family plants: cabbage, collards, kale, broccoli, cauliflower, Brussels sprouts, turnip, radish, mustard, and ornamentals such as cleome, ornamental kale, flowering cabbage and stock.[2][3][4]
- When mustard-family plants are scarce they also feed on squash, beans, tomato, okra, asparagus, potato and some fruits such as grape, peach and pear.[2][3][4]
- Harlequin bugs don't transmit plant diseases.[4]
Health risk
Harlequin bugs are plant feeders. Their bright colors warn predators that they taste bad, from compounds they take up from their host plants, and they give off a foul odor when handled, so wear gloves.[3][4]
Control
Prevention
Plant a trap crop of mustard, radish, kale or cabbage and destroy the bugs that gather on it. In Virginia trials, mustard was the plant harlequin bugs chose most consistently over collards and reduced feeding injury on the collards; a trap crop left unattended can build the population instead.[3][4][5]
Sanitation
After harvest, remove or till under old cole crop plants and crop residue so fewer adults survive the winter.[1][3][4]
Control wild mustards and other weeds such as pigweed and lambsquarters around the garden early in spring.[1][3][4]
Traps and physical control
Handpick bugs and egg clusters and drop them into soapy water; fall and early spring, before populations build, are the most effective times.[2][1][3][4]
Lay old cabbage or turnip leaves on the ground; harlequin bugs gather underneath and can be destroyed.[4]
Biological control
Egg predators such as lady beetles, lacewings, minute pirate bugs and spiders, plus parasitic wasps, give some control, but the bugs' bad taste and hard bodies limit predation of nymphs and adults.[3][1][4]
Pesticides
UC IPM generally doesn't recommend insecticides for stink bugs in gardens. If you use one, choose a product labeled for the crop and for bugs, aim at nymphs, which are easier to kill than adults, and don't spray plants in flower.[1][2][3][4]
Trap crop research
Virginia Tech field trials found that adding a systemic insecticide to a mustard trap crop gave no extra control of harlequin bug over 10 weeks in spring.[5]
USDA-ARS trials found that females on a mustard border still moved to nearby collards to lay eggs. Leaving about 2.3 meters (two unplanted rows) between the mustard and the collards cut egg-laying on the collards fourfold and feeding damage about 2.5-fold in fall plantings.[6]
Where sources disagree
Adult size: NC State and New Mexico State say 1/4 to 3/8 inch; UC says 3/8 inch; Kansas State says 1/2 to 5/8 inch.[2][3][1][4]
Generations: NC State says two to four a year in North Carolina; New Mexico State says two to three in the southern states, and Kansas State two or three.[2][3][4]
Eggs per female: NC State says up to about 155 and New Mexico State up to 164; Kansas State says 300 to 500.[2][3][4]
Nymph stages: NC State and Kansas State say five; New Mexico State says five to six; UC says four or five molts.[2][4][3][1]
Common questions
- What are the black-and-white striped eggs on my kale?
- Tiny white barrel-shaped eggs with black bands, laid on end in a double row, are harlequin bug eggs; crush them or scrape them into soapy water.[2][3][4]
- Why are my collards covered in white blotches?
- Cloudy white or yellow blotches on cole crops often come from harlequin bugs sucking out plant juices; check leaf undersides for the bugs and eggs.[1][2][4]
Sources
- University of California Statewide IPM Program, “Harlequin Bug (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/harlequin-bug/ (accessed 2026-11-11)
- NC State Extension, “Harlequin Bug (PDIC Factsheets, revised January 2025).” content.ces.ncsu.edu/harlequin-bug (accessed 2026-11-11)
- New Mexico State University Cooperative Extension Service, “Guide H-259: Harlequin Bug.” pubs.nmsu.edu/_h/H259/ (accessed 2026-11-11)
- Kansas State University Research and Extension, “Harlequin Bug (MF3135, June 2014).” bookstore.ksre.ksu.edu/pubs/MF3135.pdf (accessed 2026-11-11)
- Journal of Economic Entomology, via PubMed, “Host plant preference of harlequin bug, and evaluation of a trap cropping strategy for its control in collard (Virginia Tech, 2013).” pubmed.ncbi.nlm.nih.gov/23448042/ (accessed 2026-11-11)
- Journal of Economic Entomology, via PubMed, “Trap cropping harlequin bug: distance of separation influences female movement and oviposition (USDA-ARS, 2021).” pubmed.ncbi.nlm.nih.gov/33704486/ (accessed 2026-11-11)
- iNaturalist, “Murgantia histrionica taxon page (order and family).” www.inaturalist.org/taxa/56756 (accessed 2026-11-11)