International HLB Conference Focused on Grower Solutions

This spring, the seventh International Research Conference on Huanglongbing (IRCHLB) was held in Riverside, California. The inaugural event was held in 2008 and funded by a grant from the U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture.

USDA researcher Tim Gottwald and University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) professor Jim Graham founded the conference. The two took turns organizing the program in 2008, 2011, 2013, 2015 and 2017. The University of California Riverside and the USDA Agricultural Research Service took over the organization of the event in 2019 and 2024.

When the conference moved to California, MaryLou Polek took the reins as steering committee chairperson. She was a graduate student of Graham’s and has held various citrus research positions over the years. Polek has been involved with the IRCHLB since its inception. She says the event has evolved along with the disease.

“Back in 2008 when the first conference was held in Florida, there was still very little known about HLB. That was when research was ramping up and funding was beginning to be awarded to study the problem,” Polek says. “The early research was looking at very basic biology and looking at things like where the bacteria was in the psyllid, how it was vectored into the citrus plant and how it moved throughout the tree. This research and the IRCHLB brought the scientists from around the world together to collaborate on the problem.”

RESEARCH TO REALITY

For the 2019 and 2024 IRCHLB, Polek says the steering committee decided the meeting should focus on immediate actions growers can take now or those they potentially will have access to within the next few years.

“After all this time and research, Florida’s citrus industry is devastated,” she says. “In Brazil, the industry is realizing their strategy of scouting, psyllid control and tree removal is not working like they hoped it would. They are looking for bigger solutions, like a resistant tree. So, we were emphatic with the scientists who presented at this conference that talks needed to be grower focused on practical solutions and management solutions. The time for basic research is over.”

The IRCHLB theme this year was transitioning research into field reality. There were 430 participants, more than 100 posters and 62 presentations given with that theme in mind.

SENSE OF SOLIDARITY

Presentations covered a wide variety of research projects. Ute Albrecht, UF/IFAS associate professor of plant physiology, provided updates on trunk-injection therapies being deployed in Florida groves. Other talks focused on breeding resistant trees and gene editing techniques like CRISPR.

Rick Dantzler, chief operating officer of the Citrus Research and Development Foundation, attended the conference and said the progression of HLB in areas beyond Florida has only added to the sense of urgency felt to find solutions.

“The vibe I sensed was one of growing anxiety of those from Brazil and California, and a new sense of solidarity between us. Why? Because Brazil is now highly infected, and it seems to be increasing at significant speed,” Dantzler says. “With California, they have psyllids in groves, but they aren’t carrying the HLB bacterium. If infection breaks out, I worry that growers won’t have the water to prevent stress on their trees, and we know what stress does to HLB-infected trees. If it was ever in doubt, there is now no question that we are each pulling for the other.”

BATTLING THE BACTERIUM

Leandro Peña, a molecular geneticist from Valencia, Spain, was one of the keynote speakers. He kicked off the conference with his findings on the HLB bacterium. Graham, who is now retired from UF/IFAS but still involved in research and planning for the IRCHLB, says Peña emphasized going after the bacterium.

“Professor Peña presented his research findings that Candidatus Liberibacter asiaticus (CLas) is a parasite infecting its hosts, citrus and the Asian citrus psyllid, without causing overt damage,” says Graham. “This enables CLas to perpetuate its lifecycle by not killing either the host or the vector. Hence, HLB is a disease of citrus I characterize as death by a thousand pinpricks. Peña’s advice is to identify and deploy in citrus trees antimicrobial peptides and other antimicrobials (exclusive of antibiotics used in human health) to reduce the titer of CLas in the phloem.”

Conversations with Peña encouraged Dantzler. “Dr. Peña is one of the world’s leading scientists on HLB,” he says. “He told me in a one-on-one conversation that he thought our strategy should be to kill CLas and reduce titer levels as much as we could and hope we could do that long enough for a sufficiently resistant or tolerant tree to solve our problem once and for all. This was comforting because this is our exact strategy and why we have gone so far in with oxytetracycline and gene-edited breeding.”

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