bottom rot fungus vs fungus

bottom rot fungus and fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
bottom rot fungus	Yes	No	No	No
fungus	Yes	No	No	No

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

bottom rot fungus: fungus causing bottom rot in lettuce
fungus: an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia

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