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Gainesville, FL 32653

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Citrus "Greening" or "Huanglongbing" disease spreads well beyond Florida to now threaten California.


Citrus Huanglongbing (HLB) or citrus "greening" disease is caused by phloem-limited, uncultured bacteria in the genus Candidatus Liberibacter. HLB is one of the most destructive diseases of citrus worldwide (1), and was considered so dangerous to U.S. citrus production that the disease agent was listed as a USDA Select Agent, or potential bioterrorist agent(2), until the disease became widespread in Florida, now affecting every county where citrus is commercially grown.

The disease is characterized by misshapen fruit, blotchy yellow mottling of leaves, corky leaf veins, and eventual tree death. HLB is spread by the Asian citrus psyllid Diaphorina citri, which became established in Florida by 1998 (3). D. citri more recently become established in Texas (4). HLB first was detected in the U.S. near Miami, Florida in August 2005, and to date has been confirmed to have spread to all citrus growing counties in Florida. More recently, HLB has been confirmed in Louisiana, and the psyllid has been found in California (refer USDA site above).

1. Coletta-Filho, HD, Takita, MA, Targon, MLPN and Machado, MA. 2005. Analysis of 16S rDNA Sequences from Citrus Huanglongbing Bacteria Reveal a Different Ca. Liberibacter Strain Associated with Citrus Disease in São Paulo. Plant Disease 89:848-852.


3. Halbert, S. E. and K. L. Manjunath. 2004. Asian citrus psyllids (Sternorrhyncha: Psyllidae) and greening disease of citrus: A literature review and assessment of risk in Florida. Florida Entomol. 87: 330-353.

4. French, J.V., Kahlke, C.J. and J. V. da Graça. 2001. First Record of the Asian Citrus Psylla, Diaphorina citri Kuwayama (Homoptera:Psyllidae), in Texas. Subtropical Plant Science, 53: 14-15.

5. Li, T. and Ke, C.. 2002 Detection of the bearing rate of Liberibacter asiaticum in citrus psylla and its host plant Murraya puniculata by nested PCR. Acta Phytophylacica Sinica 29:31-35,

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