Cereal disease is a term used to describe diseases that affect cereal crops, such as wheat, barley, and rye. Two of the most common cereal diseases are ERGOT and SMUT. ERGOT is a fungus that infects cereal grains and can cause serious health problems if ingested. SMUT is a type of fungus that causes black spots on cereal grains, reducing their quality and yield. Both of these diseases can be prevented by proper crop rotation and fungicide treatments.