black-stem rust A disease that affects a wide range of cereals and other grasses. Symptoms include the appearance on stems and leaves of patches of reddish-brown spores. The causal agent is a fungus, Puccinia graminis; this organism requires two hosts to complete its life cycle, the other host being the barberry (Berberis).

black-stem rust A disease which affects a wide range of cereals and other grasses. Symptoms include the appearance on stems and leaves of patches of reddish-brown spores. The causal agent is a fungus, Puccinia graminis; this organism requires two hosts to complete its life cycle, the other host being the barberry (Berberis).