a fungous disease of cereals and wild grasses caused by Claviceps purpurea, family Clavicepitaceae, which attacks the inflorescence, replacing the grains with black or dark purple, club-shaped, horny structures (sclerotia) which are harvested with the grain and must be removed before the grain is used for flour or feed, parasiitseen; selle seene mügar, nt rukkil