Black (Stem) Rust

Pathogen

Puccinia graminis f.sp. tritici

Hosts

Puccinia graminis f.sp. tritici is specific to wheat.

Symptoms

Despite its name, the characteristic symptoms are brown sporulating pustules occurring in stripes on leaves and stems. Later in the season, black elongate pustules containing the teliospores develop, mainly on the stems.

Life Cycle

black-steam-rust-life-cycle.gif

The fungus produces teliospores on the wheat plant which produce a secondary spore, the basidiospore. This spore infects a completely different host - in this case the barberry (Berberis spp.). A further spore stage, the aeciospore, is produced on the barberry which can spread and re-infect the cereal host. This infection gives rise to the uredospore stage which produces the normal symptoms on wheat. Outbreaks in Britain are caused by air-borne spores originating in SW Europe and N. Africa so infection can only be found when appropriate air movements occur. The optimum temperature is in excess of 20°C so suitable air movements must be associated with high temperatures. Temperatures below 15°C inhibit the disease so it rarely develops under UK conditions.

Importance

The disease is very rare in the UK but may occur late in the season. Losses due to the disease in the UK are presently very small.

Cultural control

In the UK cultural control measures are generally not applicable to this disease. However, where the disease does occur commonly the removal of the alternate host is an established method of cultural control. In the USA efforts have been made to breed resistant varieties but the development of new races of the disease tend to overcome the resistance very quickly. There is no information on variation in varietal resistance in the UK

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