powdery mildew

noun

Updated on: 20 Apr 2018

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

Recent Examples of powdery mildew from the Web

Also keep a fungicide handy to apply as needed — Hydrangeas often suffer from powdery mildew and leaf spots.

— tom maccubbin, OrlandoSentinel.com, "Find the ideal spot to plant hydrangeas," 14 Apr. 2018
The spores of such fungal diseases as black spot, rust and powdery mildew may be lurking on dead leaves or atop old mulch.

— debbie arrington, sacbee, "How to grow better roses? Start now," 12 Jan. 2018
Topping that list: spider mites and powdery mildew.

— debbie arrington, sacbee, "What’s wrong with your marijuana plant? They know," 3 Feb. 2018
Fungal disease: Cool nights and hot, sunny days may result in powdery mildew on some of your susceptible roses.

— rita perwich, sandiegouniontribune.com, "Roses: Proper pruning can bring a burst of fall blooms," 31 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'powdery mildew.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.