一、关于侵染的研究早期的研究工作侧重于探索病菌侵入的集中时期,为药剂保护预防病菌侵入与发病提供依据,但未获预期结果。五十年代,国外的林病工作者在杨树等林木树皮溃疡病的研究中发现,外观无任何症状的树皮上有溃疡病菌寄居。在环境适宜、植株生长正常时,侵入的病菌潜伏于树皮中,只有在植株移植到不适宜的环境或遭受冻旱灾害生 First, the study of infection Early research focused on exploring the focus of germ invasion, provide a basis for the prevention and control of drug intrusion and pathogenesis, but did not get the expected results. Fifties, foreign forest workers in the poplar and other tree bark ulcer disease study found that the appearance of any symptoms of bark canker resident. In the right environment, plant growth is normal, the invasion of bacteria lurking in the bark, only in plant transplants into an unsuitable environment or suffer from cold and drought damage