powdery mildew

American  

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.

---

powdery mildew British  

noun

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

---

powdery mildew Scientific  

/ pou′də-rē /

1. 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.

---

Etymology

Origin of powdery mildew

An Americanism dating back to 1885–90

Compare meaning

How does powdery-mildew compare to similar and commonly confused words? Explore the most common comparisons:

• downy mildew vs. powdery mildew

Example Sentences

When tested on wheat, these compounds helped protect against fungal infections such as powdery mildew.

From Science Daily • Oct. 12, 2025

While diseases such as early blight and powdery mildew are already well-known by gardeners, they are appearing more frequently, especially for those in northern climates who are experiencing warmer weather than in prior years.

From Salon • Mar. 14, 2024

Maples are prone to many diseases, such as anthracnose, verticillium wilt, and powdery mildew, but I am still confused, so I call Brian Crooks, a forester with the Western Pennsylvania Conservancy.

From New York Times • Nov. 24, 2022

Honeysuckle vines are not drought-tolerant, and if they’re planted in a hot, dry location, they’re often plagued with powdery mildew and aphids.

From Seattle Times • Jul. 23, 2022

It is particularly valuable for the powdery mildew of many plants, especially gooseberry, carnation rust, rose mildew, etc.

From Manual of Gardening (Second Edition) by Bailey, L. H. (Liberty Hyde)