Wheat rust is a common and serious disease, reducing crop yields both in the United States and in other wheat-growing areas of the world. The disease is caused by the parasitic fungus Puccinia graminis, and can affect both the leaf and stem of wheat plants.

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In individual fields, wheat rust can account for crop loss up to as much as 40%, should weather conditions be favorable for fungus growth. Rust infections usually appear as yellow, orange, red, rust, brown, or black pustules on leaves, young shoots, and fruits.

This fungus produces two types of fruiting bodies during its life cycle, aecia and pycnia. These structures produce different types of spores (aeciospores and pycniospores, respectively), which are transmitted from one plant to another by the wind. The pycniospores parasitize wheat while the aeciospores can infect other plants.