Comparison of visual assessment and polymerase chain reaction assay testing to estimate the incidence of the huanglongbing pathogen in commercial florida citrus

Michael S. Irey, Tim Gast, Tim R. Gottwald


Huanglongbing (HLB = citrus greening) is one of the most serious diseases of citrus worldwide. The disease is caused by species of bacteria in the genus Candidatus Liberibacter and was discovered for the first time in the United States in Florida in August, 2005. To date, the Asian form of HLB, caused by Candidatus Liberibacter asiaticus, is the only form of HLB that has been found in Florida. Molecular detection protocols are available for the detection of HLB but due to the uneven distribution of the bacterium in trees, the serological variability of the pathogen, and perceived limitations of testing methodology, molecular testing generally has been limited to the confirmation of visible infections and not for detection of infections in non-symptomatic plants. In this study, visual surveys were compared to the testing of trees with a real-time polymerase chain reaction-based assay (real-time PCR). The incidence of infection based on real-time PCR testing may be up to two times the incidence of infection estimated by visible symptoms alone.


Citrus greening; real-time polymerase chain reaction; PCR; Candidatus Liberibacter

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283