Objective Gonggan(Citrus reticulata blanco var. Gonggan)production is one of the pillar industries in Renhua County, Shaoguan City, Guangdong Province. In recent years, the planting area of Gonnggan has been scaled up gradually. In 2019, Renhua County Citrus Industrial Park was selected as the one of the second batch provincial modern agricultural industrial parks in Guangdong Province. However, the investigations and researches of major diseases on Gonggan in the region have not been reported in details.

Method The QPCR(probe)detecting system and(RT— PCR)method were used for the detection of Huanglongbing(HLB)and citrus virus diseases(Citrus tristeza virus, CTV; Citrus tatter leaf virus, CTLV; Citrus exocortis viroid, CEVd; Citrus yellow vein clearing virus, CYVCV)separately on 150 samples from Renhua County. Besides, some of the fungal diseases in the field were more severe, therefore, conventional fungal separation methods and the common primer transcription interval of fungi, ITS, were used to isolate the main pathogens and identify the molecular biology of diseased samples collected from the region.

Result The average positive rate of HLB on C. reticulata blanco var. Gonggan samples collected in April 2019 was 13.2% and below 17% in October 2019 except for those in the unsupervised garden on Huangkeng Village, Huangkeng Town. It is worth noting that the positive detection rate of citrus HLB rose from 18.2% in April 2019 to 87.5% in October, while that in the orchards of Gebu Village, Danxia Street increased from 6.7% to 14.3%. Meanwhile, the average positive detection rates of CTV in April 2019 and October 2019 were 41.2% and 100%, respectively. None of other virus diseases were detected. Besides, citrus cancer, citrus anthracnose and citrus brown spot disease also occurred in this region, and they were more serious in some individual orchards.

Conclusion There is a certain degree of occurrence of citrus HLB in Renhua County. The damages of HLB on citrus industry can be reduced and the abundant year and production life of citrus orchards be extended as much as possible through comprehensive prevention and control measures, such as the classified control of high-quality and high-yield sustainable development with strengthening field management as the focus. However, CTV on C. reticulata blanco var. Gonggan has a high incidence rate, which suggests that the detection of CTV shall be conducted during citrus seedling production or before planting. And it is recommended to strengthen the scientific prevent and control of citrus anthracnose and citrus brown spot disease, rational drug use and reduction in chemical pesticides in this region.