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从有杜鹃花枯梢病的病株上分离到Ｐｈｙｔｏｐｈｔｈｏｒａｃａｃｔｏｒｕｍ，在温室内，病菌的游动孢子悬浮液喷布植株的幼嫩组织均能致枯梢病。嫩梢上的病斑在２～３天内发展成浅褐色至暗褐色的病斑。游动孢子不会侵染无伤植株上的老组织，但侵入到植株体内的菌丝能穿过幼嫩组织而在老组织中定殖。老叶片上的楔形斑就是因病茎中的病菌穿过叶柄而产生的。病原菌在感病的寄主组织内部能产生卵孢子。病组织保湿１２小时后，在被感染的组织内形成孢子囊。
Phytophthoracactorum is isolated from diseased plants with rhizome cucumbers. In the greenhouse, the young tissues of zebra spores sprayed with germs are able to cause shoot blight. Young shoots on the lesion in 2 to 3 days developed into light brown to dark brown lesions. Zoospores do not infect old tissues on non-injured plants, but mycelia invaded into the plant colonize old tissues through young tissues. The wedged spots on the old leaves are caused by the bacteria in the diseased stems passing through the petioles. Pathogens can produce oospores in susceptible host tissues. After the diseased tissue is moisturized for 12 hours, a sporocyst is formed in the infected tissue.