Grain disease is a type of plant disease that affects the production of grains, such as wheat, barley, and rye. Two common grain diseases are SMUT and ERGOT. SMUT is caused by a fungus that infects the grain and causes it to become discolored and form black spores. ERGOT is caused by a fungus that infects the grain and produces a toxin that can be harmful to humans and animals if consumed. Both SMUT and ERGOT can reduce crop yields and cause economic losses for farmers.