Two harelquin bugs

Harlequin bug (Murgantia histrionica)
Photo: Dr. Mike Raupp

Updated: May 17, 2021

This pest is most often found on cabbage family members (broccoli, cauliflower, collards, kale, horseradish, etc.) It is very partial to cleome, an annual flower. It is a true bug (has a triangular-shaped thorax) and sucks leaf sap leaving small white spots known as stipples. Leaves wilt and turn brown from prolonged feeding. 

Appearance

  • Eggs: 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.
  • Nymphs: Rounded and black, with pale green markings which soon turn brilliant red and yellow. Five instars (growth stages between two periods of molting in the development of a nymph).
  • Adults: Shield-shaped body, up to 3/8" long, brightly colored, typically black and yellow or black and red— color patterns vary with the season.
  • Harlequin bug egg mass
    Photo: Dr. Mike Raupp

    Harlequin bug eggs
  • Harlequin bug nymphs and feeding injury (stippling)
    Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

    harlequin bug immatures and feeding damage called stippling

Life cycle/habits

  • Adults overwinter in sheltered locations in or near gardens, including winter crops and organic debris.
  • In spring, adults emerge and deposit eggs on leaf undersides.
  • Nymphs and adults feed by piercing leaves to suck nutrients.
  • Harlequins are a stink bug and adults will produce a smelly odor when disturbed.
  • They love the annual flower, cleome.
  • Two or three generations occur per year.

Host plants

  • Cole crops (a.k.a. crucifers or brassicas) such as cabbage, broccoli, cauliflower, turnip, collards, horseradish, arugula.
  • Many other crops may be affected, including asparagus, bean, cantaloupe, onion, pea, potato, squash, and tomato, as well as fruits such as grape, peach, pear, and raspberry.

Signs/symptoms

  • White spots, known as stipples, result from the piercing-sucking feeding of nymphs and adults.
  • Leaves brown and look tattered.
  • Plants may wilt, be deformed, or, under severe infestation, die.

Monitoring

  • Turn leaves over to spy egg clutches.
  • Watch leaves for white or yellow blotches, distortion, and browning.
  • The bright colors of nymphs and adults makes them easy to spot, though they will hide under leaves when threatened.

Prevention/control

  • Clean up the garden at season's end. Remove all crop debris to eliminate overwintering sites.
  • Search out and manually crush eggs, nymphs, and adults.
  • Use floating row cover to exclude this pest.
  • Spray nymphs with insecticidal soap alone or in combination with pyrethrum or use neem oil.
  • Cleome can be grown as a trap crop. Spray infested cleome with an insecticide or pull plants up and dispose of in black trash bags.
  • Check catalogs for resistant varieties of many cruciferous plants.