1983年在歙县发现菊花霜霉病,为害药用贡菊品种(Chrysanthemum mroifolium Ramt.)春季发病多成苗幼造枯死或成弱苗,秋季发病整株枯死。1985年冬发病2000余亩,防治差的,减产70—90%.危害之重,为国内外所罕见, 菊花叶片、嫩茎、花梗和花蕾发病。病叶褪绿,叶背和嫩茎长满白色菌层.病叶自下而上枯死. 病菌初步定为Peronospora danica Gaum.,但菌层白色,较厚.孢囊梗分杈3—5次,第一分杈不对称,大小为28.6 Chrysanthemum downy mildew was found in Lixian County in 1983, and Chrysanthemum mroifolium Ramt., Which is a disease-damaging medicinal plant, died in spring when it became more or less dead. More than 2000 acres of winter disease in 1985, poor control, cut 70-90%. Harmful weight, rare at home and abroad, chrysanthemum leaves, tender stems, peduncles and buds incidence. Sick leaves chlorotic, leaf back and tender stems covered with white fungus layer. The diseased leaves died from bottom to top. The bacteria initially set Peronospora danica Gaum., But the fungus white, thick. The first bifurcation is asymmetric and has a size of 28.6