Downy Mildew
/DOW-nee MIL-dyoo/🦠 Diseases●● Intermediate
Also known as: peronospora
A group of plant diseases caused by oomycetes (water moulds, not true fungi) that produce a soft, downy growth of sporangiophores on the lower leaf surface. Unlike powdery mildew, downy mildew thrives in cool, moist conditions and typically causes yellowing (chlorosis) on the upper leaf surface corresponding to the downy growth below. It affects grapes, cucurbits, lettuce, impatiens, and many other crops.
Etymology
Middle English douny (soft, fluffy) + Old English meledēaw (honeydew, mildew)
Example
“Downy mildew devastated impatiens plantings worldwide starting in 2011, causing many growers to switch to resistant alternatives.”