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Exotic plant disease: Karnal Bunt
Quality wheat depends on you!
Watch out for bunt
Australia has a well-deserved reputation for marketing quality wheat to the world. It depends on grain merchants and farmers to inspect the wheat and take action if they see any problems.
This advice sheet will help increase Australia’s ability to detect the wheat disease Karnal bunt, (which is not present in Australia). An incursion of this disease could severely disrupt international trade and have a major economic impact on the wheat industry. Our aim is to make you aware of what Karnal bunt looks like so that during your normal activities you will recognise suspect grains and know who to contact for follow-up action.
Your participation is vital in helping to prevent Karnal bunt from becoming established in Australia.
Karnal bunt: in brief
Karnal bunt is caused by the fungus Tilletia indica, which infects grains at flowering and is favoured by cool humid conditions.
Karnal bunt replaces part or all of the wheat seed with a black powder that smells foul, like rotting fish. It is a disease of bread wheat, durum wheat and triticale. It occurs in India and some neighbouring countries and has moved to Mexico and more recently to some parts of America. In these countries, it can reduce grain quality by causing an objectionable odour and taste to the grain and to products made from the grain.
Karnal bunt is not readily detected in the field because usually, only a few grains in a head are partially bunted. The disease is more easily found in grain after harvest.
Symptoms of Karnal bunt overlap with those of common bunt, black point and sometimes with loose smut, diseases that do occur in Australia. So, if you see something suspicious, it is more likely to be one of these. However, it is essential that you check, and if in any doubt, alert the appropriate person in your State's Department of Primary Industries or Agriculture.
Detect, Distinguish and Act!
- Examine the grain.
- Look for discoloured grey or black seeds and 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.
- 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.
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.
What to do
If you see any grain that you suspect has Karnal bunt:
- Take a two cup grain sample, and
- report suspect detections to your local department of primary industries or agriculture by calling the Exotic Plant Pest Hotline on 1800 084 881.
Important! Do not mix suspect grain with other grain.
After contacting your local department of primary industries or agriculture, you will be advised as to a course of action and samples will be analysed to determine if it is Karnal bunt.
10 Nov 2008