Stem rust of wheat: Puccinia graminis

Stem rust is caused by a fungus. The fungus produces symptoms on almost all above-ground parts of the plant, especially the stem and leaf sheathes. At the initial stages of the disease, long, narrow streaks of red, dusty spots (pustules) are formed on all green parts of the plant. These spots are brick red in the beginning and become black at maturity. Moisture and warm weather favour the development of this disease, which usually appears at the heading stage. The fungus weakens the plant by taking its nutrients.

In nature, stem rust disease requires a living host for its growth and reproduction and cannot exist independently. The disease arrives at a new plant after being spread by the wind, usually travelling from the hills to the plains. Stem rust is favoured by hot days, mild nights and rain or dew that causes leaves to become wet. The disease can spread to healthy plants via running water, for example rain splash or water channels. The overuse of nitrogen also favours the development of the disease.