Blackleg and soft rot are bacterial diseases that, in some years, causes heavy losses in Kentucky potato patches. They may cause missing hills when it destroys the seed piece or the sprouts before they emerge from the ground. The bacteria can also cause serious rotting of tubers in the hill and in storage.
Hartman, John R. and Nesmith, William C., "Blackleg and Soft Rot Disease of Potato" (1985). Agriculture and Natural Resources Publications. 68.