① Wax gourd: The diseased plant is dwarfed, with mosaic, curved leaves and top withered, resulting in severe death.
② Cucumber variety Suyo: When cotyledons are unfolded, the juice is inoculated. After 25 ~ 32℃ and14 ~ 28 days, the diseased seedlings are dwarfed, with bright veins and rolled leaves.
In vitro stability:
① Lethal temperature: 84℃.
② Survival period in vitro: 3d(4℃).
Electron microscopic observation: the study on the subcellular distribution of the pathogen showed that the pathogen existed in the nucleus and plasma membrane (Takahashietal., 1982). Electron microscopic observation showed that all the cell walls of diseased cucumber were deformed, in addition, the chloroplasts of diseased leaf cells disintegrated and the membrane system was obviously denatured (Kojimaetal., 1983).
Quarantine risk assessment: The pathogen of this disease, Hop Dwarf Virus, can be transmitted through the propagation materials of hops for a long distance, without vector transmission, which seriously harms hops. It has occurred in China. When the risk assessment was carried out in Ji Liang, the risk value was 6, and it was a low-risk quarantine pest.
Distribution: all over the world (Europe, USA, China, Japan) (Sanoetal., 1986). Japanese hops were originally planted in Tohoku (northern Honshu), Nagano and Hokkaido. Almost all beer gardens in Northeast China and Nagano are popular with hops dwarf disease (Sasaki &; Shikata， 1980）。 Cucumber ginkgo disease is only reported in the Netherlands, and all greenhouse cucumbers are sick (Vandorst &; Peters， 1974）。 Grape strains, detected from many grape varieties, have an incidence rate of about 85%.
Quarantine countries and regions: New Zealand, Australia, Indonesia, Algeria, Iceland, Morocco, Slovakia, etc.
Plants to be inspected: hop asexual propagation materials.
Quarantine measures: When importing hop asexual propagation materials, it is required to attach the Quarantine Certificate of the exporting country to ensure that there is no such virus. After entry, it can be used for production and planting only after inspection and confirmation of no disease.