INVESTIGATION AND IDENTIFICATION OF CITRUS EXOCORTIS DISEASE IN FUJIAN PROVINCE

The bark symptoms of susceptible rootstock and the results of identification by indicator plant showed that the exocortis disease of citrus have occurred in Fujian Province. In 4 out of 21 major citrus-producing counties,18 out of 131 cultivars presented typical exocortic symptoms with diseased rates of 10-100%. Trifoliate orange(Poncirus trifoliata (L.)Raf.)rootstock was highly susceptible, but mandarin cv. Fuju (Citrus reticulata Blanco)rootstock widely distributed in Fujian was tolerant. The incubation period of infected tree was more than 5 years. The scions collected from citrus trees with or without symptoms were indexed by the indicator plant including Etrog citron Arizona 861 or Arizona 861-S-1,or Gynura aurantiaca.The indexing data indicated that the major citrus cultivars in Fujian such as madarin cvs. Ponkan, Satsuma, Fuju, sweet orange cvs, Sekken,Xinhuicheng and other cultivars such as Gailiangcheng were infected by CEV. The disease was distributed in 9 counties, i. e., Fuzhou, Minqing, Jianyan, Jian’ou, Shaxian, Yongchun, Zhangzhou, Zhangpu, Nanjing. It is possible that this exocortis was introduced into Fujian from Sichuan Province,and that the agent comprised of some different strains. In Fujian, quarantine and eradication of diseased seedlings and trees of citrus are the key to controlling exocortis disease.Decontamination of budding tools and other tools is also an effective measure to reduce the spread of disease.