Download a free copy of the Adobe Acrobat Reader. It is caused by a fungus called Tilletia indic a. Infected portions of the kernel are replaced with masses of dark, powdery, fishy-smelling, fungal teliospores. Infected kernels are fragile and easily break open to release the teliospores.
Karnal bunt is difficult to detect in the field.
Typically, only a few kernels per head are infected. There may be a slight swelling or darkening of infected florets, but this is easily overlooked. Therefore, Karnal bunt is easiest to detect by analyzing harvested grain. Yield losses from Karnal bunt are usually minor, but grain quality may be reduced because teliospores impart an unpleasant odor. Grain with more than three percent bunted kernels is usually considered unsatisfactory for human consumption.