HLB Citrus Disease

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On November 22, 2019, the California Department of Food and Agriculture (the CDFA) declared a new quarantine zone following the detection of the citrus disease Huanglongbing (HLB), or citrus greening, in a single citrus tree in Montclair's Sphere of Influence.

 

The CDFA has set a 5-square mile quarantine boundary around the find site, which links up with existing quarantines in Los Angeles and Orange Counties.  HLB quarantine maps for San Bernardino and Los Angeles counties are available online here.

 

Quarantines are already in place for HLB in portions of Los Angeles, Orange and Riverside counties.  This is the first time the plant disease has been detected in San Bernardino County.  CDFA is working with the United States Department of Agriculture (USDA) and the San Bernardino County and Los Angeles County agricultural commissioners on this project.

 

MAP 1, below, shows the current regional HLB quarantine areas ─ the Montclair quarantine area is represented by the bubble attached to the larger quarantine area for Los Angeles and Orange Counties:

 

MAP 1

Regional Quarantine Areas (Los Angeles, Orange, Riverside and San Bernardino Counties

 

HLB Citrus

 

In addition to the 5 square mile quarantine around the detection site, a half-mile mandatory treatment area has been triggered, as indicated in Map 2, attached.

HBLmontclair

The quarantine prohibits the movement of all citrus nursery stock or plant parts out of the quarantine area.  Provisions exist to allow the movement of commercially cleaned and packed citrus fruit.  Fruit that is not commercially cleaned and packed, including residential citrus, must not be moved from the property on which it is grown, although it may be processed and/or consumed on the premises ─ these fruits generally include oranges, lemons, grapefruits and kumquats.

 

HLB, considered the most devastating bacterial disease of citrus, affects the vascular system of citrus trees and plants.  It is spread through feeding action by populations of Asian citrus psyliid (ACP), Diaphorina citri Kuwayama.  ACP is an insect pest that is native to Asia.  It has appeared in Central and South America, the Caribbean and Mexico.  In the United States, ACP has also been found in Alabama, Arizona, Florida, Georgia, Hawaii, Louisiana, Mississippi, South Carolina, and Texas.  HLB does not pose a threat to humans or animals.

 

Symptoms of HLB include yellow shoots with mottling and chlorosis of the leaves, misshapen fruit, fruit that does not fully color, and fruit that has a very bitter taste that renders it unfit for human consumption.  Symptoms, however, do not often appear until two years after infection, making HLB difficult to contain and suppress.  The bacterium that causes the disease, Candidatus Liberibacter asiaticus, blocks the flow of nutrients within the tree, causing the tree to starve to death.  There is no cure, and tress infected with the disease will die two to five years after infection.  The ACP also causes injury to host plants via the withdrawal of large amounts of sap as they feed, and via the production of large amounts of honeydew, which coats the leaves of the tree and encourages the growth of sooty mold, which blocks sunlight from reaching the leaves.

 

In determining how to respond, the CDFA employs integrated pest management principles that include cultural, biological, physical, and chemical control methods.  In considering all relevant factors, the CDFA has determined that the imminent threat posed by HLB-positive trees warrants the physical method, or removal and destruction of the infected trees, followed by a course of treatment within the treatment zone.  Typically, infected trees are destroyed upon discovery.  However, due to the length of time it takes for symptoms to appear, new infestations easily spread.  If the Montclair infestation is not abated immediately, HLB could become established throughout the area and contribute toward a statewide HLB infestation.

 

Unabated, the spread of HLB would have severe consequences to the state's citrus industry and the urban landscape via the decline of citrus trees and the citrus industry.  Additionally, if unabated, the establishment of HLB in California would harm the natural environment as commercial and residential citrus growers would be forced to significantly increase pesticide use.

 

CDFA staff have scheduled removal of the infected tree and are in the midst of a treatment program for citrus trees to knock down Asian citrus psyllid infestations within one-half mile of the find site.  By taking this action, a critical reservoir of the disease and its vectors will be removed, which is essential to protect surrounding citrus from this deadly disease.

 

The resident of the property has been advised that the infected tree is subject to mandatory removal.  In addition, residents of properties in the treatment area will be invited to a public meeting where officials from the CDFA, Department of Pesticide Regulation, Office of Environmental Health Hazard Assessment, and the San Bernardino County Agricultural Commission will be available to address concerns and questions.  Residents will be notified in writing at least 48 hours in advance of any treatment applied in accordance with the Food and Agricultural Code, Sections 5771-5779 and 5421-5436.  Notice of treatment is valid until November 2020, which is the timeframe necessary to determine that the treatment was successful.

 

Residents within the quarantine area are urged to take several steps to help protect citrus trees:

 

  • Do not move citrus plants, leaves, or foliage into or out of the quarantine area or across state or international borders. Keep it local.

     

  • Cooperate with agricultural officials placing traps, inspecting trees, and treating for the pest.

     

  • If you no longer wish to care for your citrus tree, consider removing it so it does not become a host to the pest and disease.

 

While the current protocol calls only for the initial tree that tested positive for the disease to be destroyed or removed, all other host trees in the surrounding treatment area will be continually monitored and tested by CDFA personnel.

 

City staff will be meeting with County representatives for a more detailed briefing on the HLB disease.

 

CDFA, in partnership with the USDA, local county agricultural commissioners, and the citrus industry, continues to pursue a strategy of controlling the spread of the Asian citrus psyllids while researchers work to find a cure for the disease.

 

Supplemental information regarding the HBL disease is attached to the City Manager's Weekly Report as Supplement 1.