An Integrated Management of Citrus Huanglongbing in Taiwan

Abstract

Citrus Huanglongbing (HLB) was first found in China in 1943. This psyllid-borne disease caused by Candidatus Liberibacter asiaticus has been devastating the citrus industry in Taiwan since 1951. In order to formulate adequate control measures of HLB, etiological and epidemiological studies on HLB have been made thenceforth. So far four strains of HLB were identified in Taiwan. The HLB disease, commonly mix-infected with citrus tristeza and/or tatter leaf viruses, causes severe yellow mottling and decline. These systemic diseases are generally controlled by the integrated management measures including cultivation of pathogen-free seedlings, elimination of inoculum sources, and management of secondary spread by vector insects. The pathogen-free nursery system has been established since 1983 in Taiwan, which is primarily important for preventing HLB and virus diseases. The pathogen-free nursery has been properly managed through improved techniques of shoot-tip micrografting for obtaining HLB/virus-free citrus budwoods. The molecular diagnostic probes and polymerase chain reaction (PCR）were developed for indexing HLB trees and vectors. The ELISA, rapid diagnostic strips, RT-PCR techniques were also made for citrus virus diseases. The transmission of psyllid was studied for management of HLB spread. In chemotherapy, three applications of 1000 ppm tetracycline could reduce disease index of HLB in field trails.