1. A smut fungus causing a smut in cereals and other grasses that chiefly affects leaves and stems and is characterized chains of sori within the plant tissue that later rupture releasing black masses of spores
   "The flag smut fungus caused distinctive streaks on the wheat leaves"

Derived forms: flag smut fungi

Type of: smut, smut fungus

Part of: genus Urocystis, Urocystis