SINCE 1828

An Encyclopædia Britannica Company

powdery mildew

noun

Definition of powdery mildew

1 : an ascomycetous fungus (family Erysiphaceae) producing abundant powdery conidia on the host
2 : a plant disease caused by a powdery mildew

See powdery mildew defined for kids

1889

First Known Use of powdery mildew

1889

Learn More about powdery mildew

Britannica.com: Encyclopedia article about powdery mildew

Seen and Heard

What made you want to look up powdery mildew? Please tell us where you read or heard it (including the quote, if possible).

show

WORD OF THE DAY

bilious

play

of or relating to bile

Words at Play

alt-5931949575ca5

'All the Feels,' All the Time

Once more, with 'feels'

alt-59480e09b8844

A Pineapple Is An Apple (Kind Of)

Pineapple once had a different, more internationally common name.

alt-594938b88b98e

Read This to Get 'Smart'

A thinking person's guide

Words From London

Essential words for Anglophiles

Ask the Editors

Is it wrong to use 'decimate' to mean 'destroy'?

Language changes

The Serial Comma

Why don't they call it the Merriam-Webster comma?

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

istock-refers-to-this-as-a-tumble-of-strawberries-which-sounded-pretty-nice-to-us

June 2017 Words of the Day Quiz

Summer's first WOTD quiz.

Take the quiz

alt-5941ad7527c3c

Yearbook Superlatives Quiz

Is that your picture under "Largest Vocabulary"?

Take the quiz

Name That Thing

Name That Thing

Test your visual vocabulary with our 10-question challenge!

Take the quiz

SCRABBLE® Sprint

SCRABBLE® Sprint

SCRABBLE® fans, sharpen your skills!

Play the game