black root rot fungus: fungus causing black root rot in apples
fungus: an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia
hepatitis a: an acute but benign form of viral hepatitis caused by an RNA virus that does not persist in the blood serum and is usually transmitted by ingesting food or drink that is contaminated with fecal matter