Aspergillus flavus causes a greenish-yellow mold growth on the surface of infected grain. However, this does not necessarily mean that the poisonous by-product aflatoxin, has been produced by the fungus. Laboratory assays are required to determine levels of contamination. Field molding and aflatoxin contamination have been associated with production stresses and insect damaged ears. Bacterial leaf blight produces narrow, parallel-sided streaks on upper leaves which run together to give plants a scorched appearance when infection is severe.
Lesions are water soaked at first, becoming tan and eventually shredding leaf tissue.
Damage is usually restricted to localized spots within fields since it is spread only in water droplets by blowing rain or field machinery. Bacteria are soilborne, and require several rainy days where water stands in whorl long enough for incubation and infection to occur. Vasey grass is a weed host for the bacterium.