mildew vs false mildew

mildew and false mildew both are nouns.

Word	Noun	Adjective	Verb	Adverb
mildew	Yes	No	Yes	No
false mildew	Yes	No	No	No

As nouns, false mildew is a hyponym of mildew; that is, false mildew is a word with a more specific, narrower meaning than mildew:

mildew: a fungus that produces a superficial (usually white) growth on organic matter
false mildew: any of various fungi of the family Peronosporaceae parasitic on e.g. grapes and potatoes and melons

Other hyponyms of mildew include powdery mildew, downy mildew.

mildew (noun)	false mildew (noun)
a fungus that produces a superficial (usually white) growth on organic matter	any of various fungi of the family Peronosporaceae parasitic on e.g. grapes and potatoes and melons
the process of becoming mildewed

mildew (verb)	false mildew (verb)
become moldy; spoil due to humidity