Worldwide distribution. In tropics and sub-tropics. On sorghum and grasses. Occasional outbreaks have been serious.
Spots merge and cause leaves to dry and die. Spores on undersides of leaves spread in wind and rain splash.
The blight survives in debris, and on 'volunteers'.
In the 1970s, in the US and elsewhere, a strain of the fungus (Race T), caused an epidemic, and resulted in ear rot, ear drop and lodging, and a large loss of yield. Race O is the common strain in the tropics and causes minor crop loss.
Cultural control: resistant varieties; remove volunteers; provide mineral fertilizers or manures; wide spacing to reduce humidity; collect trash at harvest, compost or feed to livestock; plough-in remains; crop rotation.
Chemical control: only use if resistant varieties are not available (main control method); use chlorothalonil or mancozeb. Apply when spots first appear.