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Foot-and-mouth disease
By Kate Glastonbury, New South Wales Grains Biosecurity Officer
Wheat blast is a serious and rapidly developing fungal disease caused by the pathogen Magnaporthe oryzae pathotype Triticum. It primarily infects wheat, but oats, barley, triticale and certain grasses can also be affected. Under ideal conditions, wheat blast can devastate entire crops, resulting in yield losses of up to 100 per cent. Although Australia remains free from wheat blast, its increasing global spread highlights the need for strong on-farm biosecurity practices and early detection.
First identified in Brazil in 1985, wheat blast quickly spread throughout South America. In 2016, it reached Bangladesh, and in 2020, it was confirmed in Zambia, marking its entry into Africa. The pathogen favours warm, humid climates (18–30°C) with prolonged periods of rainfall, which makes parts of Australia’s northern grain-growing regions potentially vulnerable.
Wheat blast can be introduced through contaminated seed and can naturally spread via wind-blown spores. There is growing concern that spores could potentially travel from South-East Asia to northern Australia via wind currents. Once established, wheat blast spreads rapidly through wind and rain, and can be further dispersed on contaminated clothing, vehicles and farm equipment.
Current chemical control options overseas have limited effectiveness against wheat blast, particularly if warm, rainy conditions persist during the critical heading period.
Early identification of wheat blast is crucial. The disease typically causes progressive bleaching of wheat heads, initially appearing as distinct patches or ‘hot spots’ within paddocks. Infected heads rapidly become silvery white, and the disease can affect all above-ground parts of the plant.
Stems and leaves may develop dark brown, eye-shaped lesions, often accompanied by dark grey spores. Grain may become shrivelled and misshapen within days of the first visible symptoms. The best time to inspect your crops for wheat blast is during the reproductive stage.
For more information, download the wheat blast fact sheet at grainsbiosecurity.com.au.
Image: Wheat head affected by wheat blast. Source: C. Cruz, Purdue University
Wheat blast symptoms may be mistaken for other plant diseases or stress factors. On cereal heads, symptoms of wheat blast can resemble several common diseases and abiotic stresses. The symptomatic bleached heads of cereals may look similar to fusarium head blight or crown rot, while lesions on leaves can appear similar to spot blotch. Wheat blast damage may also be confused with drought stress or micronutrient deficiencies.
Accurate identification is essential in its control and eradication, and any suspicious symptoms should be reported immediately to the Exotic Plant Pest Hotline on 1800 084 881.
Image: Typical eye-shaped lesions on wheat leaf. Source: C. Cruz, Purdue University
To safeguard against wheat blast, growers should implement rigorous on-farm biosecurity measures. Essential steps include:
Early detection and rapid reporting are vital. Contact your local Grains Biosecurity Officer or call the Exotic Plant Pest Hotline on 1800 084 881 immediately if you notice unusual symptoms.
The Grains Farm Biosecurity Program aims to improve the management of, and preparedness for, biosecurity risks in the grains industry at both the farm and industry levels.
Launched in 2007, this program is managed by Plant Health Australia and funded by growers through Grain Producers Australia together with the New South Wales, Queensland, South Australian, Victorian and Western Australian governments.
