Powdery Mildew
/POW-der-ee MIL-dew/🦠 Diseases● Basic
Powdery mildew is caused by various species of obligate parasitic fungi (Erysiphales) that produce distinctive white to gray powdery growth on leaf surfaces, stems, and sometimes flowers. Unlike most fungal diseases, powdery mildew thrives in dry conditions with moderate temperatures and high humidity (not wet leaves). Affected plants show reduced photosynthesis, distorted growth, and premature leaf drop.
Etymology
From Old English pudor (powder) + Old English meledēaw (honeydew)
Example
“The garden phlox showed classic powdery mildew — white patches coating the upper leaf surfaces in late summer.”