The pathogen responsible for scab is primarily determined by geographic location. In the U.S. corn belt Fusarium graminearum is the pathogen. In other areas F. aveneceum, F. culmorum, and F. nivale are the causal agents. These pathogens can also cause seedling blights and crown rots in wheat depending on environmental conditions. Scab is initiated by infection of floral parts, glumes, and spikelets during warm, wet weather.
Plants are most susceptible at anthesis.
Infection leads to development of shriveled and moldy grain. Spikelets distal to infection may be barren or contain very shriveled grain, but not contain the pathogen. Infected grain contains mycotoxins harmful to livestock and humans. Control is primarily through crop rotation. Rotations should have a non-host between corn and wheat.