The Causes And Management Of Chlorosis Symptoms Of Citrus In Yongchun County, Fujian Province

Yongchun county of Fujian, is the famous for "township of citrus" in China. The rate of citrus which have chlorosis symptoms is up to 10% in the county in 2007. A survey on major cause of large range of chlorosis symptoms of citrus was conducted for the last three years in Yongchun county.The research showed that there are many causes lead to the large range of chlorosis symptoms of citrus in Yongchun county. Citrus Huanglongbing(HLB) is the most important cause for the large range of chlorosis symptoms of citrus. The detection rates of Candidatus Liberibacter asiaticus are all above 90% for suspicious plant by molecular biological diagnosis. That citrus Huanglongbing occur widespread and serious in Yongchun county.The results also revealed for the first time that the citrus nematode(Tylenchulus semipenetrans) is widely distributed in citrus producing regions in Yongchun county and appeared to be a major cause of large range of chlorosis symptoms of citrus. In the random survey conducted in 12 town, infested rate of citrus orchards is 69.6%,The percentage of infected citrus is 33.4%. The nursery stock infected by Tylenchulus semipenetrans is one of the important reason for the wildly spread in Yongchun county.Damage by Anoplophora chinensis is widely happen in Yongchun county, but. it always happened in the orchards which management is relatively weak and cause serious damage. In the investigation, nutrient deficiency, waterlogging damage, fertilizer damageand damages are also reason for chlorosis symptoms of citrus orchards, but it mainly happened in the low levels of orchard management. the migration of village-labors in Yongchun county is the important reason for the low levels of orchard management.Based on the causes of chlorosis symptoms of citrus in Yongchun county, combined with experience of author, the proposals on preventing and controlling the citrus yellows were put forward.