在青海省,馬鈴薯晚疫病引起块茎腐烂比地上部感染远为普遍和严重。例如,1960年叶面枯死率不到1％,而块茎腐烂則达10％左右。 1963年用塑料布复盖土表,并在縫隙处噴洒1％硫酸銅的隔离試驗証明,凡是地上部与地下部隔离的各处理,地下块茎均未感染晚疫病,而未隔离的地下块茎均有不同程度的感染(表1)。这說明引起块茎腐烂的病原菌是由地上部落下, In Qinghai Province, tuber rot caused by late blight of potato is far more common and severe than that of aerial parts. For example, in 1960, the rate of death of leaf foliage was less than 1%, while tuber rot was about 10%. In 1963, a plastic sheeting covering the soil surface and isolating the gap with 1% copper sulphate showed that none of the underground tubers were infected with the late blight and all the underground tubers that were not isolated were isolated from each other. All had different levels of infection (Table 1). This shows that the pathogen causing tuberous stems is fallen from above ground,