Flag Smut of Wheat

Urocystis agropyri


Grey, long, raised streaks with black powdery spores on the leaf blades, sheaths and sometimes on the stems. The streaks rupture the leaf tissue revealing a mass of powdery grey to black spores which rub off the leaf readily. Leaves may become twisted and split lengthwise.

Infected plants are usually stunted and produce numerous tillers, some of which may lodge with age. Heads often fail to emerge or produce poor grain.

Species Affected:


Barley and Oats are not affected.


Seed and soil borne.

Disease will survive in the soil for 2 years or more.

Spores are dispersed from Wheat straw by wind during harvest.

Grain contaminated during harvest will carry the disease to the next crop.

Infection can occur before the crop emerges and early sowing into warm dry seed beds favours infection.

Life Cycle:

Origin and History:



Management and Control:

Sow resistant varieties. See Disease Susceptibility of Wheat Varieties

Use seed from uninfected areas.

Treat seed of susceptible varieties that will be planted into contaminated paddocks with a fungicide for soil borne Flag Smut.

Sowing clean seed into a contaminated paddock will not control the disease and a fungicidal seed dressing for soil borne disease is required.


3-5 infected plants per hundred plants indicates that the soil is contaminated with disease spores and following wheat crops are likely to be heavily infected. Collect plants at heading to determine the levels of disease.

Related and Similar Species:



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