Mirids

Mirids are a key pest of mungbean and cotton.

Scientific name

Creontiades dilutus (green mirid)
Creontiades pacificus (brown mirid)
Sidnia kinbergi (crop mirid)

Other names

Crop mirid is also called Australian crop mirid.

Description

Highly mobile insects 7–8mm long with long antennae. Adults have clear wings folded flat on the back.

  • Green mirid adults are pale green (often with red markings). Nymphs have a pear-shaped body and the antennae tips are reddish-brown.
  • Brown mirid adults are similar to green mirids, but the front part of the body is brown. Nymphs have banded antennae, alternating red-brown and white.
  • Crop mirid adults are grey-green on top and bright green underneath. Nymphs are green with brown- and white-striped antennae and a black spot on the back.

May be confused with

Apple dimpling bug, broken backed bug, Rutherglen bug, brown smudge bug, black-headed mirid, bigeyed bug

Distribution and habitat

Widely distributed across Australia.

Hosts

  • A pest of cotton, lucerne, mungbean, navy bean, peanut, soybean, faba bean, adzuki bean, sunflower and safflower.
  • Also feed and develop on a wide range of other host plants, including many common weed species such as wild turnips, verbena and thistles.

Damage

Adults and nymphs pierce plant tissue and release a chemical that destroys cells in the feeding zone:

  • In cotton, growing points can be killed resulting in increased branching. Squares, buds, flowers and small bolls can be shed, decreasing yield potential. Boll feeding can reduce lint yield and quality.
  • In legume crops, mirids may also attack more mature pods, feeding on and damaging the seeds inside without causing shedding.

Life cycle

  • Individual eggs are inserted into the leaf or petiole and hatch after 4–10 days.
  • Nymphs have 5 instars (stages), each about 2–3 days duration.
  • Adults can live for 3–4 weeks.
  • Mirids can overwinter in low numbers on weeds or wild hosts. Local movement into summer crops occurs as alternative host plants dry off.
  • Early season storm fronts may bring influxes of adults that have matured in inland Australia.

Monitoring and thresholds

Check crops twice weekly from budding until post-flowering:

  • inspect visually or use a beat sheet
  • avoid sampling in windy conditions.

Populations are reduced by:

  • sustained hot weather (3 consecutive days above 35°C)
  • heavy rains or storms.

Natural enemies

Damsel bugs, bigeyed bugs, predatory shield bugs, as well as lynx, night stalker and jumping spiders feed on mirid adults, nymphs and eggs.

Control measures

No resistance to insecticides has been detected in Australia.

Minimise flowering duration by optimising water management.

Further information