Pseudoperonospora humuli

Hops Downy mildew Pseudoperonospora humuli Bordeaux mixture, copper oxychloride, copper sulphate + sulphur... 

When oat roots were used for bioassay, zoospores were first attracted and then caused lysis which raises the possibility that oat crops and their residues might be used to reduce soil populations of zoosporic plant pathogens. The cystospores were insensitive to concentrations of saponins or oat root extract that lysed zoospores. The zoospores lytic principle in oat root extract/exudate was believed to be a saponin, avenacin (61). The effects of avenacin (61) or root extracts on zoospores were identical to those of /0-aescin and consistent with a role of membrane active agents. Toxic effects of saponins on zoospores were also observed in Pseudoperonospora humuli Miyabe Takah. and Phytophthora spp. [139,140]. 

Downy mildew is caused by the fungus Pseudoperonospora humuli (Miyabe and Tak.), G. W. Wilson. It was first observed in Japan in 1905 and in the United States in 1909. At that time hops were grown in the United States along the east coast and the incidence of downy mildew was one of the major factors which determined the transfer of the hop-growing industry to the west coast. In Britain the disease was unknown before 1920 but since then it has spread to all the hop-growing areas and some infection can be found in most gardens. Epidemics can readily occur under suitable weather conditions if control measures are not carried out. As discussed above, new varieties resistant to downy mildew are now available. 

Peronospora tabacina Plasmopora viticola Pseudoperonospora humuli... 

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