Seven entities recently received $21.7 million to conduct research into combating and preventing HLB at the farm level. The funding is from the U.S. Department of Agriculture's National Institute of Food and Agriculture (USDA NIFA) Emergency Citrus Disease Research and Extension program.
The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) received the majority of the funding, more than $16 million.
PROJECTS LED BY UF/IFAS
The largest grant, at approximately $8.6 million, is for development, evaluation and delivery of citrus HLB management approaches by targeting its nature as a pathogen-triggered immune disease. The principal investigator is Nian Wang. The goal is to develop HLB management approaches for existing groves and non-transgenic HLB-resistant and HLB-tolerant citrus varieties.
Other UF/IFAS projects are:
- A coordinated network for the improvement of HLB research and Extension outputs, funded at $2 million. Megan Dewdney is the principal investigator. The project tackles the task of gathering and organizing the research findings available to growers.
- Targeted production of non-transgenic HLB-tolerant trees through complementary approaches, funded at approximately $1.5 million. Zhonglin Mou is the principal investigator. The first goal of this project is to produce non-genetically modified HLB-tolerant citrus trees by editing or silencing the promising target genes.
- HLB-resistant rootstock candidates for the citrus industry: Validating and understanding disease resistance, funded at approximately $1.2 million. The principal investigator is John Chater. This project will advance knowledge about why some rootstocks appear to be more tolerant to HLB than others.
- Providing individual protective covers and brassinosteroids to prolong health and improve fruit yield and quality in newly planted trees, funded at $800,000. Fernando Alferez is the principal investigator.
- Toward a reliable insect cell culture-based technique for culturing CLas bacteria (the causative agent of HLB), funded at approximately $793,000. Kirsten Pelz-Stelinski is the principal investigator. The project aims to have a culture system that serves as an essential research tool for increased understanding of CLas biology and for effective, rapid screening of antimicrobial agents against CLas.
- Accelerating the delivery of conventionally developed HLB-tolerant citrus scions and rootstocks as pathogen-free budlines for replicate multi-site testing, funded at approximately $536,000. The principal investigator is Jude Grosser. Successful adoption of this technology will reduce the current clean-up time by 1.5 to 2 years, and significantly increase the number of selections that can be processed.
PROJECTS LED BY OTHER INSTITUTIONS
- Virus-induced gene silencing using insect specific viruses to manipulate psyllids as a strategy to control HLB is a University of California-Davis project led by Yen-Wen Kuo.
- A method for generating an optimally attractive scent for Asian citrus psyllid biocontrol is a University of Connecticut project led by Alexander Aksenov. UF/IFAS' Lukasz Stelinski is a co-investigator.
- Endophytes as sources of antimicrobials to control HLB is being led by Kateel Shetty of Florida International University.
- Scalable low-cost organic nanocarriers for efficient foliar uptake of registered anti-HLB agents is a Purdue University project led by Kurt Ristroph.
- Citrus yellow vein-associated virus induced gene silencing vector for vaccinating seedlings and controlling HLB in infected fruit-bearing trees is a University of Maryland project led by Anne Simon.
- Molecular strategies to block psyllid transmission of the HLB pathogen is a USDA Agricultural Research Service project led by Michelle Heck.
Sources: USDA NIFA and UF/IFAS
Deformed HLB-infected fruit
To ensure California citrus growers are well prepared in the event of a potential commercial grove detection of Huanglongbing (HLB), the deadly citrus plant disease that can be spread by the Asian citrus psyllid (ACP), the Citrus Pest and Disease Prevention Program (CPDPP) has developed a response guide for growers to utilize and educate themselves on the California Department of Food and Agriculture's (CDFA) action plan.
The Response Guide for a Confirmed HLB Positive Detection in a Commercial Grove details the steps taken by CDFA and actions required of the property or grove owner, as outlined in CDFA's Action Plan.
The actions in the response guide represent the most effective tools known to the citrus industry at this time and are meant to protect California's citrus groves and support CDFA's current required regulatory response. While, as of today, there have been no positive detections of HLB in a commercial citrus grove, the CPDPP recognizes the importance of proper preparation.
In addition to the requirements outlined in the guide, growers are encouraged to use as many methods as feasible for their operation in order to limit the spread of the ACP and HLB.
To read or download the response guide, please click here. If you have any questions or would like to order physical copies of this response guide, please visit our Resources page.
SANTA BARBARA COUNTY CITRUS UPDATES
The next Area Wide Management coordinated grower treatment window will be in January. Be sure to renew permits as needed with the County Agriculture Department. Growers are also encouraged to work with your pest management professionals to stay vigilant with regular monitoring of your trees for ACP, especially young trees and along grove perimeters. Research shows that in generally infested areas like Santa Barbara County, keeping ACP populations low reduces the risk of citrus trees acquiring the bacteria that causes the deadly HLB disease.
Please consider removing citrus that is no longer being cared for or is not worth the resources required to protect it from ACP & HLB.
Biological Control Releases
Monthly releases of the ACP biological control agent Tamarixia radiata continued in October in residential areas of Santa Maria, Guadalupe, and Orcutt in the northern part of the county, and to the south in Goleta, Santa Barbara, Montecito, Summerland and Carpinteria.
En Español -- Spanish Language ACP/HLB Presentations
Las grabaciones de video y solamente audio están disponibles a continuación para nuestras presentaciones en español ACP / HLB desde el 27 de septiembre de 2022. Francisco Macías, asesor local de control de plagas, dio una presentación general sobre ACP y HLB, y Rafael Raygoza de la oficina agrícola del condado de Ventura presentó sobre las inspecciones. El evento fue moderado por Maureen McGuire de la Oficina Agrícola del Condado de Ventura y el Grupo de Trabajo ACP / HLB. Muchas gracias a nuestros presentadores y moderador por proporcionar esta valiosa información en español.
Video and audio-only recordings are available below for those who missed our Spanish language ACP/HLB presentations on September 27, 2022. Francisco Macias, a local pest control advisor, gave a general presentation on ACP and HLB, and Rafael Raygoza with the Ventura County Agricultural office presented on inspections. The event was moderated by Maureen McGuire from the Ventura County Farm Bureau and ACP/HLB Task Force. Muchas gracias to our presenters and moderator for providing this valuable information in Spanish.
HLB Quarantine Update
As of October 28, a total of 3,942 trees and 501 ACP have tested positive via PCR for the bacterium that causes HLB. Trees that test positive are treated for ACP and removed, and the HLB quarantine may be expanded. Additional ACP treatments and HLB detection surveys are conducted on a recurring basis to remaining citrus within 250 meters of each detection.
Counties where HLB has been detected via PCR testing are Los Angeles, Orange, San Diego, Riverside, San Bernardino and San Diego, with the majority of detections in Orange County. Recent expansions of the HLB quarantine occurred in Riverside and Orange counties. To see a map of the current HLB quarantine areas, and other details of locations and numbers of HLB detections, please visit maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf.
To help you prepare for the regulatory impacts of HLB, please refer to CDFA's Information for Citrus Growers/Grove Managers, Action Plan for ACP and HLB or this summary flier for information on regulatory and treatment requirements growers can expect when HLB is detected in or near your citrus grove or packing house.
Upcoming CPDPC Meetings -- Webinar and In Person
All meeting agendas and eventually the minutes are posted at www.cdfa.ca.gov/citrus committee/. All meetings are free and open to the public to listen to or make public comment. Meetings are currently in person and accessible via phone and/or webinar. Links to register for and join meetings are included in agendas when posted.
- The Nov 2 Operations Subcommittee has been cancelled.
- Outreach Subcommittee, November 2 at 1:30 pm. Agenda and instructions to join are here.
- Finance Subcommittee, November 8 at 9 am. Agenda and instructions to join are here..
- CPDPC Full Committee, November 9 at 10 am. Agenda and instructions to join are here. .
For a list of current committee members, click here.
Additional ACP/HLB Resources
- CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
oUC IPM recommendations for ACP
oWeb-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
oVideo on Best Practices in the Field, available in English and Spanish
oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
oSign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
oRegulatory requirements for moving bulk citrus: Information for Citrus Growers
oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)
Translating the science of managing HLB
Your resource for learning about existing and new tools being developed by researchers to protect and manage citrus from the causative agent of huanglongbing (HLB).
See how scientists are working to control HLB by reading short snapshots about their research. Topics include:
Click on the links below to explore the snapshots!
We have the answers!
Growers and end-user audiences can use this PowerPoint presentation which has been tailored for their use. It provides general background on the genetics that are used to modify crops and information on state and national regulatory approaches and consumer attitudes.
Examples of the questions that are addressed:
- What are the general processes of genetically modifying plants and insects?
- When and where did huanglongbing (HLB) come from?
- What are some genetic approaches to controlling HLB?
- What is consumer response to engineered crops and foods?
- Author: Brad Buck, UF/IFAS
LAKE ALFRED, Fla. — Sometimes in science, a new perspective brings an “a ha!” moment. That's what one senior researcher at the University of Florida Institute of Food and Agricultural Sciences believes happened with his latest research on Huanglongbing (HLB), or citrus greening.
HLB is worldwide, devastating citrus disease caused by Candidatus Liberibacter asiaticus (CLas), a bacterium that settles into the tree's phloem — its interior vascular system — eventually killing the tree. Since first found in Florida in 2005, it has infected virtually every grove in Florida and cost the citrus industry billions of dollars.
UF/IFAS' Nian Wang's most recent research describes in detail how HLB causes damage to citrus trees and presents the case that HLB is a pathogen-triggered immune disease. A pathogen-triggered immune disease is a disease that results from the activation of an organism's immune cells fighting a pathogen (a virus, bacteria, or parasite) that invades an organism, in this case, the citrus plant.
This is the first time that this explanation of HLB symptoms as pathogen-triggered immune responses has been presented and defended. Seeing HLB in this new context may mean finding new solutions to the disease, faster. Pathogen-triggered immune diseases have not been reported in the world of plants that includes over 250,000 species but are common in humans.
Scientists don't fully understand how the pathogen that causes HLB damages infected citrus plants because it has not been cultured in artificial media. With this new evidence that supports a premise that HLB is an immune-mediated disease, researchers can see new light on how to manage HLB.
Through his research Wang, has shown HLB infection stimulates systemic and chronic immune responses in phloem tissue, especially overproduction of reactive oxygen species (ROS), which are part of the plant's immune response. Chronic and excessive ROS production is responsible for systemic cell death of phloem tissues, which in turn causes HLB symptoms. This supports the hypothesis that HLB is an immune-mediated disease.
Antioxidants and immunoregulators are commonly used to treat human immune-mediated diseases. They halt or reduce the process that results in cell death. In citrus, the researchers tested whether growth hormones like gibberellin acid (GA) and antioxidants (uric acid and rutin) could impact cell death triggered by the infection and, therefore, block or reduce HLB symptoms.
The researchers found the GA and uric acid had an encouraging positive impact on infected trees. This has also been supported by other research in process at the UF/IFAS Citrus Research and Education Center.
“Our findings allow us to control HLB by mitigating ROS with integrated horticultural measures, genetic improvements of citrus varieties with antioxidant enzymes, generating non-transgenic HLB resistant/tolerant citrus varieties by editing key genes required for CLas-triggered ROS production, and using CTV-mediated expression of antioxidant enzymes and silencing of key genes required for CLas-triggered ROS production,” said Wang, a professor of microbiology and cell science at UF/IFAS.
Wang's research also tested existing grove management practices that integrate antioxidants, micronutrients (activating antioxidant enzymes), gibberellin (mitigating ROS, regulating immune response, and promoting new growth) and optimized fertilization and irrigation (reducing ROS production) that are available in Florida. All the products tested, except the antioxidants, have already been registered for citrus production, thus can be easily adopted by citrus growers.
Wang's research has also identified the RBOHD gene to be the main producer of CLas-triggered ROS. With this, the researchers can now “edit (using CRISPR technology)” or “silence” RBOHD or specific receptor gene(s) responsible for RBOHD activation and the resulting cell death of phloem tissues and HLB symptom development. It is expected these approaches will allow economic and efficient citrus production in HLB endemic citrus production regions such as Florida and Texas and provide the long-term solution against HLB for all citrus production regions of U.S. (including California) in case that HLB becomes endemic in the future.
Read the whole story:
Key Points About Plant "Immunity"
Unlike vertebrates, plants do not have an adaptive immune system. Nonetheless, plants can launch specific, self-tolerant immune responses and establish immune memory.
To promote virulence, pathogens inject effector molecules that target conserved immune signalling hubs into the plant cell. In response, plants have evolved resistance (R) proteins that detect effector-induced perturbations in these hubs, providing the potential to specifically recognize a large number of pathogens with similar infection strategies through a smaller number of R proteins.
Intraspecific and interspecific plant crosses suggest that autoimmunity can arise from self-reacting R proteins, illustrating the threat of uncontrolled R protein activity. Dynamic transcriptional and post-transcriptional regulation of R protein levels is thought to minimize the risk of autoimmunity in plants.
Pathogen-infected tissues generate a mobile immune signal consisting of multiple proteins as well as lipid-derived and hormone-like molecules. These signal molecules are transported to systemic tissues, where they induce systemic acquired resistance (SAR). SAR is associated with the systemic reprogramming of thousands of genes to prioritize immune responses over routine cellular requirements.