The infected citrus tree infected with the disease Huanglongbing in the Hacienda

California has had one confirmed case of the disease Huanglongbing, found in a citrus tree (pictured) in the Hacienda Heights neighborhood in the Los Angeles, Calif. area in 2012. The tree was immediately destroyed.

HLB early detection technologies show promise, but no silver bullet

Citrus industry leaders are diligently working and committed to early detection research for the disease Huanglongbing or HLB, and are pressing forward as quickly as science allows. 

Guest commentary

As the Asian citrus psyllid (ACP) continues to spread throughout California, monitoring for Huanglongbing (HLB), the fatal tree disease that the psyllid can spread, is a top priority for state agriculture officials and commercial citrus growers.

Trained California Department of Food and Agriculture (CDFA) HLB surveyors are collecting plant and insect samples from all over Southern California and the Central Valley. To date, there has only been one confirmed HLB-positive tree in the Hacienda Heights area of Los Angeles in 2012.

Unfortunately, growers are getting mixed messages about the efficacy of methods to detect HLB in citrus trees. Currently, the U.S. Department of Agriculture identifies only one approved detection method for the disease – the polymerase chain reaction (PCR) test employed by CDFA.

Confirmation of the disease via PCR is necessary to ignite regulatory actions, including mandated tree removal.

HLB has a long latency period and it can take years for a tree to show symptoms and test positive for the disease. This long waiting period has led many in the citrus industry to become eager for a sound early detection technology (EDT) to be developed that can detect HLB before a tree is symptomatic.

Industry leaders, including the Citrus Research Board and Citrus Pest & Disease Prevention Program, are investing in research to evaluate new tests.

Recently, for example, potential EDTs were tested in a research study conducted in Texas. The results of the first trial were inconclusive. However, some methods showed considerable promise and are being reevaluated.

No scientific proof

Despite this hopeful work, there is currently no scientific proof to justify the reliance on any of the new methodologies being tested. We’re simply not there yet.

It is important to remember that CDFA shares plant samples gathered through its monitoring program with researchers exploring the validity of other detection methods. This collaborative approach brings us one step closer to identifying valid ways to detect HLB in California citrus trees.

While so many of us are eager to identify a valid EDT, we can’t rush into applying technologies that don’t meet the rigorous federal standards needed to take regulatory action. Industry leaders are diligently working and committed to EDT research and are pressing forward as quickly as science allows.

Growers throughout the world hope that EDT and-or resistant rootstock would provide solutions to manage this disease.

Until researchers identify methods that prove to be as effective as the approved PCR test – and justify mandated tree removal – we must remain proactive in the fight to control the spread of the ACP and put trust in the PCR testing taking place throughout California. 

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