University of Maryland Extension

Harlequin Bug - Vegetables

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Orange and black bug on broccoli, cauliflower, and kale

harlequin eggs and nymphs
Harlequin bug (Murgantia histrionica) 
Photo: Dr. Mike Raupp

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 eggs
Egg cases

harlequin bug eggs and nymphs
Newly hatching eggs

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.

harlequin bug damage
Stippling damage caused by harlequin bugs

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 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.

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