CDFA warns SoCal residents of another ‘highly invasive’ pest threatening citrus plants

The plant disease known as Huanglongbing (HLB) is believed to be caused by a phloem-restricted bacterium which is vectored by the Asian Citrus Psyllid (ACP). (CDFA)

First came the fruit flies. Now, the California Department of Food and Agriculture has issued a warning about another “highly invasive” pest causing disease in citrus fruits across Southern California.

The Huanglongbing (HLB) or Citrus Greening pathogen (Candidatus Liberibacter asiaticus) is found predominantly in Asia but has also been reported in several U.S. states as well as the Caribbean, Mexico and other parts of Latin America.  Since being discovered in Florida in 2005, it has been positively identified in Louisiana in 2008, South Carolina in 2009, and in Texas and California in 2012, CDFA officials said. 

According to the CDFA, HLB can be “difficult to detect” since the host plant may remain symptomless for months or even years before showing signs of infection. 

“An early symptom of the disease is blotchy yellow asymmetrical mottling of the leaves,” the CDFA’s Huanglongbing pest profile said. “More advanced symptoms include twig dieback, stunting and decline in the tree’s health to the point where the tree bears only a few, small, deformed fruits that are poorly colored and bitter tasting. Tree mortality usually occurs several months to years after infection.” 

The plant disease is spread between trees by the Asian Citrus Psyllid and can be hosted on nearly all citrus plants and hybrids, CDFA said, making it much more dangerous than regular pathogens. 

“HLB has been described as the most devastating disease of citrus in the world,” Food and Agriculture Department officials said. “HLB affects almost all citrus cultivars and causes substantial economic and environmental losses to the citrus industry as well as residential backyard citrus by shortening the life of trees and making fruit and juice inedible.” 

This aerial image taken on March 14, 2023 shows a tractor carrying oranges driving through an orchard in Arcadia, Florida. In Florida, the world’s second largest producer of orange juice after Brazil, orchards have been suffering from a citrus tree disease, Huanglongbing (HLB), for the last 17 years. A bacteria spread by the insect Asian psyllid causes the disease, which makes trees produce a green, bitter fruit that is unsuitable to sell, before dying within a few years. (Photo by CHANDAN KHANNA/AFP via Getty Images)

The CDFA cited a study in Florida that found that HLB increased citrus production costs there by 40 percent and led to the citrus industry losing over $1.3 billion in revenue.

Currently, there are no “curative methods” to control HLB and there are no chemical controls that specifically target the bacterium, officials said, which limits options on disease control. 

“Comprehensive control measures for HLB focus largely on prevention of infection by eradicating infected plants, controlling the vector, Asian Citrus Psyllid and the production and planting of HLB-free trees,” the Department of Food and Agriculture said. 

Several quarantine areas which CDFA officials have outlined can be viewed in the map below:

Several quarantine areas throughout Southern California have been outlined by CDFA officials. (CDFA)

More detailed depictions of the quarantine boundaries can be found by clicking here and then clicking a grid number on the map.

For more information, consult the California Department of Food and Agriculture’s Citrus Pest and Disease Prevention Division website.

This is not the Golden State’s first recent interaction with invasive bugs; the discovery of the Tau fruit fly, an exotic insect native to Asia that targets cucurbits, avocado, tomatoes and peppers in addition to citrus, prompted officials to quarantine an upscale neighborhood in Santa Clarita in July.

Queensland fruit flies, which come from Australia and feed on pome and stone fruits, dates, avocado, melons and tomatoes in addition to citrus fruits, were first discovered in SoCal in October and led to authorities establishing another quarantine area in a Thousand Oaks neighborhood.

To report an unusual plant or pest in your area, use the CDFA’s Report a Pest Web App or fill out this form.

In addition, the CDFA’s pest sighting hotline can be reached by calling 1-800-491-1899.

Click here to watch a video outlining how to check citrus trees for the Asian Citrus Psyllid.

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