also: くろぼ
noun
A fungal disease of cereal plants, characterized by black, powdery spore masses on the ears.
今年の麦は黒穂病にやられてしまった。
This year's barley was hit by smut disease.
Compound of 黒 (kuro, 'black') and 穂 (ho, 'ear of grain'), referring to the blackened ears caused by the fungus.