Kernels of infected plants are replaced by masses of dark brown smut spores.

Occasionally smut sori may also develop in leaf blades, where they appear as long streaks.

Infection is seed-borne within the seed, the fungus penetrating the endosperm while the grain is being formed.

Spores are sticky in nature when present inside the membrane due to oily coating.

At least 13 pathotypes are known; virulence is governed by at least three single recessive and independent gene pairs.