The yield and quality of pear are greatly taken from virus desease as viruses infecting and accumulating in the pear tree while continually asexual propagation.

• 梨树在长期的无性繁殖过程中，感染并积累了多种病毒。分布较广泛的有梨环纹花叶病毒、梨脉黄病毒、苹果茎沟病毒，榅桲矮化病毒等。