also: ろきんびょう
noun
downy mildew
A plant disease caused by oomycete pathogens, appearing as downy growth on leaves. Technical term used in agriculture and botany.
今年は雨が多くて、キュウリにべと病が発生した。
With all the rain this year, downy mildew broke out on the cucumbers.
べと病の予防には、風通しを良くすることが大切です。
To prevent downy mildew, it's important to ensure good air circulation.
Powdery mildew, a different fungal disease that appears as white powdery spots, unlike the downy growth of べと病.
The term べと病 derives from べとべと (sticky, damp) describing the downy, moist appearance of the mildew, combined with 病 (disease). The kanji form 露菌病 literally means 'dew fungus disease'.