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Causal organism - Urocystis agropyri
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The teliospores released from the leaves can either be blown onto grain of healthy plants, contaminating the grain or they can drop to the soil where they are very persistent, surviving up to 4 years. When contaminated grain is sown or if healthy grain is sown into contaminated soil the teliospores germinate, producing a secondary spore type - the sporidia. These spores infect the germinating wheat seedling's coleoptile. The fungus, having penetrated the seedling then grows inside the plant, eventually producing the typical striping on the upper leaves late in the season, giving rise to a new generation of teliospores. The teliospores can survive in soil for several years so even where a break from cereals occurs, susequent wheat crops may become infected.
Importance
Flag smut of wheat occurs in some european countries and in the major wheat producing countries of Australia, Canada and the USA. However, it was not known to be present in the UK until 1998 when an outbreak was confirmed in Essex. The disease in itself is not particularly damaging unless present at high levels but it can have serious consequences with regard to exporting grain or wheat products. Many countries have quarantine restrictions which prohibit the importation of wheat products from countries where the disease is established.
