powdery mildew

noun
1.
any of various parasitic fungi of the ascomycete order Erysiphales, which produce a powderlike film of mycelium on the surface of host plants.
2.
Plant Pathology. a disease caused by powdery mildew, characterized by yellowing and death of the foliage and a white mealy growth of fungus on the surface of above-ground parts.

Origin:
1885–90, Americanism

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
powdery mildew
 
n
1.  a plant disease characterized by a superficial white powdery growth on stems and leaves, caused by parasitic ascomycetous fungi of the family Erysiphaceae: affects the rose, aster, apple, vine, oak, etc
2.  any of the fungi causing this disease

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
powdery mildew   (pou'də-rē)  Pronunciation Key 
Any of various important plant diseases caused by fungi, especially those of the family Erysiphaceae, which produce powdery conidia on the surface of the hosts leaves and stems.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

powdery mildew

plant disease of worldwide occurrence, caused by many specialized races of fungal species in the genera Erysiphe, Microsphaera, Phyllactinia, Podosphaera, Sphaerotheca, and Uncinula. Hundreds of species of trees, shrubs, vines, flowers, vegetables, fruits, grasses, field crops, and weeds can be affected by powdery mildew.

Learn more about powdery mildew with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Powdery mildew occurs worldwide in cool, humid, and semiarid areas where cereals are grown.
Spider mites and a disease called powdery mildew can make life miserable for roses growing in greenhouses.
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