Fighting for Citrus Industry

Continuing to Fight For Citrus Industry’s Longevity Requires Teamwork

By Jim Gorden, Committee Chair, Citrus Pest and Disease Prevention

For more than two centuries, citrus has grown strong in California’s yards and groves—serving as a source of nourishment, income, and tradition for many different individuals—but the citrus industry is at risk due to Huanglongbing’s (HLB) growing presence in California.

Jim Gorden

In 2018, HLB was found in more than 600 residential citrus trees in Southern California, and despite the program’s thorough surveying efforts, HLB has not been found in a commercial grove, but we must continue to hold strong. It has never been more important for all of us— including the Citrus Pest & Disease Prevention Program (CPDPP), regulatory authorities, the citrus industry, the scientific community, and others—to work together to prevent the spread of the disease and save California’s citrus industry.

While much has changed since the citrus industry came together ten years ago to support the creation of the CPDPP, one constant remains: the program’s dedication to fighting HLB. This year, the Citrus Pest & Disease Prevention Committee (CPDPC) created a strategic plan for combatting HLB now and in the future. The plan identified five prioritized strategies to achieve CPDPP’s goals of keeping HLB out of commercial groves, limiting Asian citrus psyllid (ACP) movement in the state and fine-tuning the program. In addition, the program agreed to align its annual budget in support of the strategies, which can be viewed in this report.

With this plan comes additional responsibilities for all individuals involved. The CPDPC understands HLB isn’t the only issue posing a threat to your business and our industry – but it’s one we can’t ignore. This report highlights the many activities the program and our partners are doing across the state to protect commercial groves from HLB, but we are only as strong as our weakest link.

Looking forward, much is at stake for California citrus growers, packers and workers as the industry faces its biggest threat yet in HLB. I encourage you to connect with the program, your local pest control district, or task force, and follow best practices for managing the ACP and HLB. If we sit idle, hoping others will take action for our benefit, we are welcoming this devastating disease into our groves.

But, by working together, we can protect California’s commercial citrus industry from devastation—sustaining our livelihood and the legacy of California citrus.

For more information on the  Citrus Pest & Disease Prevention Program Click here.

Huanglongbing Discoveries in California

Recap of Huanglongbing Cases in California

News Release

Huanglongbing has now been confirmed in numerous communities in Los Angeles and Orange counties. These detections are disheartening, but the Citrus Pest & Disease Prevention Program, California Department of Food and Agriculture and county agricultural commissioners are taking aggressive steps to remove all diseased trees and educate homeowners about this critical threat to California citrus.

Here is a recap of the Huanglongbing activity in California to date:

Hacienda Heights:

HLB+ Trees = 2

HLB+ ACP = 1 (on the initial HLB detection site)

San Gabriel:

HLB+ Trees = 56

HLB+ ACP = 4 (on HLB+ tree sites)

Cerritos:

HLB+ Trees = 2

HLB+ ACP = 2 (1 on HLB+ tree site, 1 on a separate site)

Rosemead:

HLB+ Trees = 0

HLB+ ACP = 1

La Puente:

HLB+ Trees = 0

HLB+ ACP = 1

La Habra:

HLB+ Trees = 1

HLB+ ACP = 0

Anaheim:

HLB+ Trees = 11

HLB+ ACP = 8 (6 on HLB+ tree sites, 2 on separate sites)

Fullerton:

HLB+ Trees = HLB+ ACP = 1 (1 on HLB+ tree site)

In response to each and every HLB positive tree detection, CDFA conducts mandatory 800-meter response, which includes surveys and sampling of all host trees, treatments and removal of the confirmed HLB infected tree.

Nursery stock in quarantine areas is placed under USDA-approved screen facilities, where it is held and tested for two years, or it is destroyed. Outreach is done to homeowners and elected officials to educate them on the severity of the issue encourage them to help stop the spread of this devastating disease.

Improved Huanglongbing Detection in Citrus Trees

Projects Underway for Better Huanglongbing Detection in Infected Trees

 

By Patrick Cavanaugh, Farm News Director

 

 

The big problem with Huanglongbing Disease (HLB), also known as citrus greening, is that an infected tree, despite having no visual symptoms, could quietly be a massive reservoir of HLB. The main vector, the Asian Citrus Psyllid (ACP), could easily pick up HLB from that tree and spread the disease throughout the orchard.

Currently, the main push to contain the possible spread of HLB is by controlling ACP. Yellow sticky traps are positioned near every commercial orchard in California, as well as near non-commercial trees in neighborhoods. Finding a psyllid on a trap triggers mandatory spray programs to help eliminate all psyllids in the area.

Neil McRoberts, Huanglongbing Detection
Neil McRoberts, associate professor of plant pathology, UC Davis

“Yes, one of the most critical questions in managing in HLB is the trees can be infected for a long time before you can visually see the ACP there,” said Neil McRoberts, an associate professor of plant pathology, University of California, Davis.

“There is a group of scientists, funded by the Citrus Research Board of California (CRB), working on different early detection methods. Those are methods where you would be able to tell the tree was infected before you could see the tree is infected,” said McRoberts.

The CRB funded field trials in Texas over the last few years that have narrowed the field of competitors to two or three techniques. The CRB will continue to fund the two leading contenders in that race to determine the leading early detection technology.

In the first technique, researchers analyzed all the microbes that live on a non-infected leaf surface and studied how that profile of microbes changes when the tree gets infected. Detecting a change in microbe profile could indicate the tree is not as healthy as it should be.

“Researchers take the microbes that live on an infected tree, extract the DNA from those microbes and run the DNA through a sequencer. The sequencer identifies which types of microbes are there,” he said.

McRoberts said sampling for microbes is easy. Researchers use an industrial-sized swab on the leaf surface. “You literally clean the leaf surface with the swab until it’s squeaky clean, put that swab in a bottle and send it to a lab. When it gets to the lab, they extract the DNA out of it and the rest of the process happens from there.

ACP Nymph Tamarixia Huanglongbing
A female Tamarixia radiata laying egg on an ACP nymph. (Photo by J. Lotz). Courtesy of Citrus Research Board

In selecting which trees should undergo microbe swabbing, McRoberts noted that the ACPs tend to attack the groves from the outer edges, inwards. “At different times of the day, the light will be on different edges of the grove depending on where the sun is and how warm it is. You can target your sampling towards the places where you’re more likely to find it, but still, finding those initial little infections is tough.”

The second method is a technique called metabolic profiling. A newly infected tree starts to produce different proteins and other chemicals in response.

Still another research strategy is analyzing things that stay in the tissue. “There’s a change in the profile of metabolites in the tree. If you run those metabolites through a mass spectrometer, the mass spectrometer will spit out a profile. You can tell the difference between a healthy profile and an infected profile,” McRoberts said.

“This is how the dogs come into the picture. Everybody knows that citrus has an odor. When the trees are infected, the profile of the chemicals and the composition of that odor change. We can’t smell it, but a very sensitive electronic detector device can sometimes pick it up. Remarkably, dogs can pick it up. We think that’s what happening with the canine detectors; they’re picking up some change in the smell of the trees.”

McRoberts said that dogs are amazingly accurate in detecting trees with HLB disease. “The best that we can tell from the trials involving dogs, the false positive rate is less than 1 in 1,000. I’m very confident with the detector dogs,” McRoberts said.

 

Featured photo: Adult Asian citrus psyllid (Photo by J. Lewis). Courtesy of Citrus Research Board

Citrus Research Board of California (CRB)

UC Davis Department of Plant Pathology