Hessian flies

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Hessian flies

Exotic to Australia

Features: Tiny mosquito-like insects that have caused serious damage to wheat
and barley crops in many parts of the world

Where it's from: Hessian flies are widespread in the USA and Europe. Other
countries such as New Zealand, Africa, the Middle East and the Russian Federation
have had detections of one or both of the pests.

How it spreads: Importation of infested crops, straw and other plant materials

At risk: Wheat, barley, triticale and rye

Both species of adult hessian fly are tiny and mosquito-like.
Scott Bauer, USDA Agricultural Research Service, Bugwood.org

Report it

Keep it out

Hessian flies (Mayetiola destructor and M. hordei) are serious pests of cereal crops and one of the most damaging insect pests in the world. It attacks the whole above ground part of cereal plants, resulting in stunted growth, less grain and a poor-quality crop. Up to 40 per cent crop losses have been recorded in severe infestations overseas, with the US and Spain reporting large amounts of damage in fields.

The fly in its adult stage is mosquito-like, just 2-4 mm long, and very difficult to control with pesticides. Females lay eggs on the upper surface of leaves, and larvae (grubs) make their way down to the leaf stem where they feed, damaging the plant.

If hessian flies were to make their way to Australia, they would damage grain crops, and some of our trading partners would reject our exports of grain and hay, to avoid importing the pest as well.

Hessian fly damage in the foreground.
John C. French Sr., Retired, Universities: Auburn, GA, Clemson and U of MO, Bugwood.org
Flaxseed-like pupae are found at the base of the plant, here wheat.
John C. French Sr., Bugwood.org


Importing goods

To keep hessian fly out of Australia, never ignore Australia’s strict biosecurity rules.

Import shipments may need to be treated and certified, so before you import, check our Biosecurity Import Conditions system (BICON).

What to look for

There are no flies in Australia that attack cereal plants above ground.  Keep an eye out for:

  • small flies 2-4 mm long
  • white to red larvae, 3-4 mm in length, feeding at the base of the plant
  • dark brown flaxseed-like pupae (cocoons) inside the base of the plant
  • stunted and discoloured plants
  • withering heads and lodging (collapse) in grain.
  • M. hordei can be also be detected by galls on barley stems.

Where to look


Infested plants, straw and other plant material is the most likely way that hessian fly would make it to Australia.

Grain growers

  • Check your wheat and barley crops frequently for the presence of new pests and diseases.
  • Keep an eye out for poor growth, flies, larvae and flaxseed-like pupae in and around plants.

What to do

If you think you’ve found hessian fly:

  • take a photo
  • contain the material without disturbing it (this may be as simple as closing the doors on a shipping container or preventing access to a field)
  • collect a sample of the insect, if it is possible to do so without disturbing the pest.

Report it

Seen something unusual? Report it. Even if you’re not sure.

Read the detail

Last reviewed: 9 February 2021
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