cedar-apple rust vs rust fungus

cedar-apple rust and rust fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
cedar-apple rust	Yes	No	No	No
rust fungus	Yes	No	No	No

As nouns, rust fungus is a hypernym of cedar-apple rust; that is, rust fungus is a word with a broader meaning than cedar-apple rust:

Other hypernyms of cedar-apple rust include rust.

cedar-apple rust (noun)	rust fungus (noun)
rust fungus causing rust spots on apples and pears etc	any of various fungi causing rust disease in plants