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Cotton harlequin bug

  • Adult with egg cluster
    Adult with egg cluster
  • Damage to cotton boll
    Damage to cotton boll
General information

The cotton harlequin bug is a member of the jewel bug family (Scutelleridae).

Scientific name

Tectocoris diophthalmus


Adults are 20 mm long and are brightly patterned in yellow, orange, red, metallic green or metallic blue colours. Nymphs are mostly metallic blue or metallic green and are found in groups feeding on open bolls or very small bolls where they can reach the seeds with their short stylets. Eggs are laid in a cluster, generally encircling a branch and are guarded by an adult.

Pest status

Minor, widespread, irregular.

Crops attacked



Bug feeding on the seeds in mature bolls allows the entry of a boll-rotting fungi that stains the lint. It is rarely a pest, as insecticides applied against other pests control it. In transgenic cotton insecticide application is reduced and the pest has become more frequent.

Risk period

In cotton this pest usually appears late in the season.


Check for adults, nymphs and eggs from squaring onwards.


The threshold for cotton harlequin bug is four adults per metre using a beat sheet. Damage can be assessed regularly from boll set to boll maturity by randomly selecting 14-day-old bolls and squashing them in the palm of the hand. Look for the presence of warts or stained lint. A threshold of 20% of young bolls damaged indicates the need for control. For current chemical control options see Pest Genie or APVMA.

Further information

Last updated 10 November 2010