Answer:
"Falscher Mehltau" is a German equivalent of "downy mildew" (Peronosporaceae family).
This particular mildew especially is dreaded by growers of such crops as hops (Humulus lupulus) and gourd relatives (Cucurbitaeceae family). It first shows up as light green to yellow spotting on foliage. But it ends up stunting growth and sabotaging any attempt at harvest.