plant disease vs disease

plant disease and disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant disease	Yes	No	No	No
disease	Yes	No	No	No

As nouns, disease is a hypernym of plant disease; that is, disease is a word with a broader meaning than plant disease:

plant disease (noun)	disease (noun)
a disease that affects plants	an impairment of health or a condition of abnormal functioning