Karnal bunt

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​​​​​​​​​​​​​​​​​​ Infected pieces of grain with karnal bunt that have black masses of spores on sections of the grain. Each piece of grain varies in the severity of infection.


Karnal bunt

Exotic to Australia

Life form: Fungus
Origin: India
Distribution: Afghanistan, Brazil, India, Iran, Iraq, Mexico,
Nepal, Pakistan, South Africa and United States of America
Features: Broken hollow grain, powdery masses of dark spores
strong fishy odour, similar to common bunt, black point, loose smut
Pathways: Wheat seeds, soil, agricultural products, machinery
At risk: Grain (wheat, durum wheat and triticale)


Karnal bunt is a highly invasive exotic grain pest which threatens Australia’s wheat industry by its potential heavy impact on the quality and saleability of infected crops.

Karnal bunt is caused by the fungus Tilletia indica which infects grains at flowering and is favoured by cool humid conditions.

If introduced into Australia, Karnal bunt would be almost impossible to eradicate as its spores can persist in soil for a considerable time, up to four years.

  • Natural spread can be substantial as spores can be carried over long distances by wind.
  • They can also pass through the digestive tracts of animals undamaged, making it possible for the fungus to be distributed with animal manure.
  • The main mode of international spread is on infected wheat seeds.

An incursion of this fungus could severely disrupt international trade and have a major economic impact on our agricultural industry, as a major exporter of wheat.

How to identify Karnal bunt

Everyone needs to keep an eye out for symptoms of Karnal bunt, which is spread through transportation of stored grain and soil, or on agricultural products or machinery.

It is easiest to detect symptoms after the grain has been harvested because there are usually only a few partially infected grains in each wheat head.

Visible symptoms of the fungus:

  • Black masses of spores on sections of the grain which crush easily into a black powder, and produce an odour like rotten fish.
  • Similarities exist with common bunt which is found in Australia, however, Karnal bunt tends to infest only part of the seed head.
Karnal bunt spores Source: PaDiL
Microscopic view of Karnal bunt infected grain. Under a microscope the spores are evident by appearing darker and misshapen.
Infested wheat head Source: forestyimages.org
A wheat head infested with karnal bunt. Often harder to detect as the wheat head usually only has a few bunted grains.


Karnal bunt can reduce grain quality by causing an objectionable odour and taste to the grain and to products made from infected grain. Only three per cent of grain needs to be infected before consumers can taste and smell the fishy odour, rendering the grain unsaleable.

Karnal bunt intensity on wheat seed (top – healthy, bottom – complete infestation)
A number of pieces of grain are displayed, showing a range in severity of infection from healthy grain to heavy infestation with large amounts of black spores.



If you work around imported goods you need to look for grain that:

  • is infected with a blackened and sooty appearance
  • gives off a ‘dead fish’ smell
  • crushes in hand producing a greasy black powder.

Also ensure that all imported agricultural machinery is clean and free of wheat seeds and other contaminants.

Growers and grain handlers

Karnal bunt is not readily detected in the field because usually, only a few grains in a wheat head are partially bunted. The disease is more easily found in grain after harvest.

Check harvested grain regularly:

  1. Examine the grain.
  2. Note any unpleasant or fishy smell. If there is an unpleasant odour but no obviously abnormal seeds, the bunt balls may have all been broken up and the spores spread throughout the grain.
  3. Look for discoloured grey or black seeds. Pick out a few of the discoloured seeds. Rub them between thumb and forefinger. Does the grain crush and release a black powder?
    • No: if the grain is dark at one end, the condition is black point. Depending on the level of black point in the sample, the grain may be downgraded (check local quality requirements).
    • Yes: if the powder has a foul smell, the grain is affected by either common bunt or Karnal bunt. Sometimes loose smut does not completely disperse before harvest and some pieces can find their way into the sample.
  4. Look at how much of the seed has been replaced by bunt. Common bunt usually replaces the whole seed, whereas Karnal bunt usually only replaces part of the seed.

Keep Karnal bunt out of Australia

All Australians and international tourists have a role to keep out exotic pests and diseases. Australia remains free of Karnal bunt and we need your help to keep it this way.

Check what you can and cannot bring into Australia, whether you are a:

Quality wheat depends on you

Australia is one of the world’s most reputable producers of high quality wheat. This favorable status depends on good biosecurity practices, including growers and grain handlers inspecting their wheat, and taking action if they see any problems.

Protect your farm from biosecurity risks and learn about import restrictions and biosecurity measures.

Some items, by law, are subject to certain import conditions to be allowed into Australia. Please check the Biosecurity Import Condition System (BICON).

Be aware of any Karnal bunt biosecurity measures that may be in place for incoming goods and conveyances. Industry advice notices are reviewed regularly and could change.

Secure any suspect specimens

Containment is critical. This can be as easy as isolating suspect grain and not mixing it with other grain. If you see any grain that you suspect has Karnal bunt, take a two cup grain sample and report it.

Report detections of exotic pests

Any detections of Karnal bunt must be reported to the authorities.

Import community

If you receive or work around goods imported from overseas, including mail, you need to be vigilant to symptoms of Karnal bunt and other exotic pests. If you see an unusual pest, secure the goods to limit the movement of the pest and immediately report it to the department’s SEE. SECURE. REPORT. Hotline 1800 798 636 or by using the online form.

Growers and home gardeners

If you see symptoms of Karnal bunt or anything unusual, report it to the Exotic Plant Pest Hotline 1800 084 881. This will put you in touch with the department of primary industries or agriculture in your state or territory.

When reporting your concern, you will be given advice on handling the specimen and what to do next until an officer can investigate.

Additional information

Last reviewed: 4 February 2020
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