As research continues to ramp up in the Animal and Plant Health Inspection Service's (USDA-APHIS) nationwide efforts to fight the spread of Huanglongbing (HLB), or Citrus Greening disease (CG), officials have announced expansion of its existing quarantine zone in Texas to include two more counties.

The expanded HLB quarantine zone wasn't the only news developments from APHIS concerning Texas agriculture last week. On a more promising note, APHIS announced they have lifted the Mexican fruit fly quarantine area imposed for Hidalgo County in South Texas earlier this year after three life cycles passed without finding additional Mexican fruit flies in the area.

For reasons unexplained, the latest APHIS notice, dated Oct. 28, was provided last week. But the quarantine for fruit flies was technically lifted in late August. APHIS and TDA report the Texas citrus industry followed program protocols and used various control actions to eradicate the transient Mexican fruit fly populations.

Both the HLB quarantine and the fruit fly quarantine have affected the movement of citrus plant material from the Lower Rio Grande Valley this year.

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The latest HLB quarantine zones in Texas were imposed last week on counties surrounding Houston in the southeastern part of the state. APHIS and the Texas Department of Agriculture (TDA) confirmed last Wednesday that Fort Bend and Montgomery counties have now been quarantined following positive detections in plant tissue samples collected from citrus nurseries in both counties.

Earlier this year APHIS/TDA imposed an HLB quarantine on Harris County after positive detections of plant material were discovered in Houston.

Five counties fully quarantined

In the most recent quarantines, samples were collected during surveys conducted as part of the cooperative Citrus Health Response Program. With the current additions, the five counties fully quarantined for HLB in Texas are Cameron, Fort Bend, Harris, Hidalgo, and Montgomery.

 APHIS is applying safeguard measures on the interstate movement of regulated articles from Fort Bend and Montgomery counties. These measures parallel the intrastate quarantine TDA imposed on September 10, 2014. This action is necessary to prevent the spread of HLB to non-infested areas of the United States. Since 2009, APHIS has regulated all of Texas for the Asian citrus psyllid, the insect that transmits HLB.

States that currently are affected by HLB quarantines include California, Florida, Georgia, Louisiana, South Carolina, and Texas. APHIS also has active HLB quarantines in effect for Puerto Rico and the U.S. Virgin Islands.

Quarantines for the Asian Citrus Psyllid (ACP) that vectors citrus greening disease has been imposed on the following states: Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, South Carolina and Texas. Quarantines for ASP also have been established in Puerto Rico, Northern Mariana Islands, the U.S Virgin Islands, and Guam.

Citrus greening, also called Huanglongbing or yellow dragon disease, is one of the more serious diseases of citrus. This bacterial disease is thought to have originated in China in the early 1900s. The disease is primarily spread by two species of psyllid insects. One species, the Asian citrus pysllid, Diaphorina citri, has been present in Florida since 1998. The bacteria itself is not harmful to humans but the disease has harmed trees in Asia, Africa, the Arabian Peninsula, and Brazil. Three strains of the bacteria are known, an Asian, an African version, and a recently described American strain discovered in Brazil.

The Asian strain, Candidatus Liberibacter asiaticus was found in Florida in early September, 2005.

To respond to the problem, USDA, APHIS, PPQ and the Florida Department of Agriculture and Consumer Services deployed a Unified Command under the Incident Command Structure, and delimiting survey crews are working in southern Florida to define the extent of the problem.

Citrus greening disease is a threat to the U.S. citrus industry. Other than tree removal, no effective control exists once a tree is infected and there is no known cure for the disease. Infected trees may produce misshapen, unmarketable, bitter fruit. Citrus greening reduces the quantity and quality of citrus fruits, eventually rendering infected trees useless. In areas of the world affected by citrus greening the average productive lifespan of citrus trees has dropped from 50 or more years to 15 or less. The trees in the orchards usually die 3 to 5 years after infection and require removal and replanting. An infected tree produces fruit that is unsuitable for sale as fresh fruit or for juice.