black root rot fungus vs fungus

black root rot fungus and fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
black root rot fungus	Yes	No	No	No
fungus	Yes	No	No	No

As nouns, fungus is a hypernym of black root rot fungus; that is, fungus is a word with a broader meaning than black root rot fungus:

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

black root rot fungus (noun)	fungus (noun)
fungus causing black root rot in apples	an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia