Wheat leaf rust, is fungal disease that effects wheat

Wheat

Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, barley

Barley

Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

 and rye

Rye

Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...

 stems, leaves and grains. In temperate zones it is destructive on winter wheat

Winter wheat

Winter wheat is a type of wheat that is planted from September to December in the Northern Hemisphere. Winter wheat sprouts before freezing occurs, then becomes dormant until the soil warms in the spring. Winter wheat needs a few weeks of cold before being able to flower, however persistent snow...

 because the pathogen overwinter

Overwinter

To overwinter is to pass through or wait out the winter season, or to pass through that period of the year when “winter” conditions make normal activity or even survival difficult or near impossible...

s. Infections can lead up to 20% yield

Crop yield

In agriculture, crop yield is not only a measure of the yield of cereal per unit area of land under cultivation, yield is also the seed generation of the plant itself...

 loss - exacerbated by dying leaves which fertilize the fungus. The pathogen is Puccinia rust fungus

Rust (fungus)

Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales. About 7800 species are known. Rusts can affect a variety of plants; leaves, stems, fruits and seeds. Rust is most commonly seen as coloured powder, composed off tiny aeciospores which land on vegetation producing...

. Puccinia triticina causes 'black rust', P.recondita causes 'brown rust' and P.sriiformis causes 'Yellow rust'.