Flag smut

Urocystis tritici

Flag smut was historically an important disease of wheat in Australia, however through the regular use of seed treatments and planting resistant varieties, it is now effectively controlled. Flag smut differs from other cereal smut diseases as symptoms appear on the leaves rather than the heads. Yield losses of 5 – 20 per cent have been recorded from flag smut.

Description

Symptoms appear on the leaves, leaf sheath, awns and sometimes stems. Flag smut is characterised by long, raised, black streaks which break through the plant tissue revealing masses of sooty grey-black spores. Plants may be stunted, leaves can appear curled and distorted, and plants can tiller excessively, with not all tillers displaying symptoms. Infected tillers generally don’t produce grain.

Flag smut is seed and soil-borne and spores can survive in the soil for up to seven years. Spores are released during harvest, contaminating grain and the soil. Spores from contaminated grain infect seedlings prior to emergence, this process is favoured by warm temps (20 °C) and early dry sowing.

Control

Preventative measures are important to control flag smut. Resistant varieties should be planted, particularly in paddocks where flag smut has been previously diagnosed.

The regular use of seed dressings provides effective control for flag smut in wheat. Several options exist including Jockey^® Stayer^®, EverGo^®; Prime , EverGol^® Energy, Raxi^® T and Hombre^® Ultra.

Jockey Stayer , EverGol Energy, Raxil T and Hombre Ultra are all registered for the control of flag smut (seed and soil-borne) in wheat and EverGol Prime is registered for the control of seed-borne flag smut and suppression of soil-borne flag smut.

Related Pests

Smut

Ustilago nuda - (loose smut barley), Ustilago tritici - (loose smut wheat), Ustilago avenae - (loose smut oats), Ustilago hordei - (covered smut oats and barley), Urocystis tritici - (flag smut wheat), Tilletia spp. – (covered smut or bunt of wheat)

Smut is a fungal disease affecting cereals crops in Australia. Commonly known as loose, flag or covered smut; hosts include wheat, barley and oats. The pathogens causing smut produce masses of soot-like spores in the leaves, grains and ears, causing significant reductions in both grain quality and yield. Each pathogen is specific to each type of cereal and therefore cannot be transferred between them. In Australia, there is a minimum to zero tolerance for grains contaminated with smut at grain receival points.

Refer to the links below for more detailed information on smut in each crop.

Loose smut

Ustilago nuda - (loose smut barley), Ustilago tritici - (loose smut wheat), Ustilago avenae - (loose smut oats)

Affecting wheat, barley and oats, loose smut is rarely seen due to the regular use of effective seed treatments. Each cereal is infected by a particular strain of loose smut, therefore loose smut in wheat cannot infect barley or oats, for example. There is a minimal to zero tolerance of grain contaminated with loose smut at most grain receival points across Australia.

Covered smut

Ustilago hordei (oats and barley), Tilletia laevis (wheat)

Covered smut is caused by the same fungal pathogen in barley and oats, but in wheat it is caused by a different pathogen. Covered smut in wheat has several names including ball smut, stinking smut and common bunt. Like other cereal smuts, covered smut is generally controlled effectively with seed dressings. Covered smut can cause yield losses and there is a nil tolerance of grain contaminated with covered smut at receival points in Australia.

Refer to the link below for more detailed information on bunt.

Bunt

Tilletia laevis, Tilletia caries

Bunt is a disease of wheat, rye and other grasses and is known by several names including common bunt, stinking bunt, stinking smut, ball smut and covered smut. Bunt is caused by two fungi species which produce masses of soot-like spores in the grains or ears. Plants may appear stunted and reductions in yield and grain quality are common. There is a zero tolerance for grain contaminated with bunt at receival points across Australia. Karnal bunt is a highly invasive disease which significantly affects grain quality, so the Australian grains industry is working hard to prevent its introduction into Australia.

Refer to links below for more information on other smuts and bunt.

References

CropPro (Viewed Nov 2019), ‘Flag smut of wheat’, http://www.croppro.com.au/crop_disease_manual/ch04s05.php

Department of Primary Industries and Regional Development (DPIRD) (2016), ‘Diagnosing flag smut of wheat’, https://www.agric.wa.gov.au/mycrop/diagnosing-flag-smut-wheat

Holloway, G (2012), ‘Bunts and Smuts of Cereals’, Agriculture Victoria, http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/grains-pulses-and-cereals/bunts-and-smuts-of-cereals

Thomas, G, Jayasena, K, Beard, C and Hills, A (2017), ‘Smut and bunt diseases of cereal – biology identification and management’, Department of Primary Industries and Regional Development (DPIRD), https://www.agric.wa.gov.au/print/node/326