It is thought to be caused by various species of Alternaria, Fusarium, and Helminthosporium, and possibly other fungal genera.
[2] The fungus forms after the seeds have set but while they are still green and it is potentiated by high humidity.
Infected areas are brown to black in color, and as the disease spreads the kernels may become shriveled.
[3] Several studies have been unable to satisfy Koch's postulates or to associated black point with fungal infection.
They have concluded that Black Point is purely a physiological disorder and that Smudge is a separate issue caused by fungal pathogens.