Fifty years ago there was a seismic shift in cut-rose production from outdoor or heated greenhouse production in Europe to cultivation under unheated glass and plastic (polythene) protection in the African highlands. Roses (Rosa species) and the mildew disease which plagues them have been around since medieval times, but the situation is complicated by two distinct and completely different types of mildew disease -powdery mildew and downy mildew. Powdery mildew disease is caused by a true fungus called Podosphaera pannosa while a fungus-like microbe called Peronospora sparsa is causal agent of downy mildew.
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