flax rust vs flax rust fungus

flax rust and flax rust fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
flax rust	Yes	No	No	No
flax rust fungus	Yes	No	No	No

As nouns, flax rust and flax rust fungus are synonyms defined as:

Other synonyms of flax rust include Melampsora lini.

flax rust (noun)	flax rust fungus (noun)
fungus causing flax rust	fungus causing flax rust