April 10, 2018

Single Breakthrough Discovery for Citrus Greening Disease in Florida Unlikely, Says New Report; Calls for a Master Plan to Coordinate Research Efforts and Management

WASHINGTON – A single breakthrough discovery for managing citrus greening in Florida in the future is unlikely, says a new report by the National Academies of Sciences, Engineering, and Medicine.  The committee that wrote the report called for a systems approach to prioritize research on the disease and strategically distribute resources for research to effectively manage the disease, which is the most serious threat for citrus growers worldwide.

The disease Huanglongbing (HLB) or citrus greening — associated with bacteria that are spread by a sucking insect, the Asian citrus psyllid — was initially observed more than 100 years ago in Asia and was first detected in Florida in 2005.  The infection results in blotchy mottling of leaves, stunting of shoots, gradual death of branches, and small, deformed fruits with bitter juice.  Although infected trees do not die right away, they can remain in a steady state of decline for several years.  Between 2010 and 2014, acreage of citrus trees in the state declined from roughly 750,000 to 476,000 acres, and production volume has declined by 58 percent since 2005.  In Florida, citrus greening has caused a cumulative loss of $2.9 billion in grower revenues from 2007 to 2014, an average of $374 million a year. 

The Citrus Research and Development Foundation (CRDF), a $124 million state citrus-industry initiative, has invested nearly 90 percent of its funds in HLB research.  CRDF asked the Academies to review its research portfolio and determine if its efforts have followed recommendations outlined in the Academies’ 2010 report, which originally called for the organization’s creation.  The committee found that CRDF was responsive to several recommendations from the previous report, and along with other funders, has advanced our knowledge about the disease. However, HLB remains a serious danger to Florida’s citrus industry, having progressed from an acute to a chronic disease throughout the state.

The report notes that significant barriers to progress toward an HLB solution still exist, among them the inability to culture the bacteria in the laboratory, the lack of advanced diagnostics for early disease detection, and the absence of standardized research methodology that would improve the comparability of results across studies.  Resolution of any one of these issues would constitute a significant step, according to the report.  

The committee recommended continuing support for both basic and applied research for short- and long-term research efforts.  In the long run, HLB solutions would likely utilize new technology, such as gene modification and gene editing, focusing on targets that mediate molecular interactions among plant, bacteria, and the vector, the committee said.  As interest in using genetic modification in research grows, CRDF should also consider funding research to assess stakeholder acceptance of the technology and expand efforts to educate growers, processors, and consumers to facilitate the eventual deployment of genetically modified citrus lines.

In the meantime, growers in the state will need short-term solutions for the industry to remain viable.  The report recommends finding the best suite of strategies to control the disease in different environmental and growing conditions, vector and pathogen pressures, tree varieties, and stages of tree health, which would help growers in Florida and other states where HLB also occurs.

The report also highlights the need to better understand the economic and sociological factors that impact decision-making and behaviors of growers, which influence the adoption of HLB management strategies. CRDF should create accessible databases to support sociological and economic modeling of citrus greening-related research outcomes and application projections. 

The report recommends researchers communicate about the outcomes and evaluation of their efforts in a timely and systematic way.  Additionally, current approaches to research prioritization and funding based within individual federal and state funding agencies have not led to development of a master plan for HLB research and subsequent management solutions.  CRDF should work with other funding agencies to create an overarching advisory panel to develop a master plan for HLB research, communication, and management. 

The study was sponsored by CRDF. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine.  The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.  For more information, visit http://national-academies.org. A roster follows.

Riya V. Anandwala, Media Relations Officer
Andrew Robinson, Media Relations Assistant
Office of News and Public Information
202-334-2138; e-mail news@nas.edu

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Copies of A Review of the Citrus Greening Research and Development Efforts Supported by the Citrus Research and Development Foundation: Fighting a Ravaging Disease are available at www.nap.edu or by calling 202-334-3313  or 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).


Division on Earth and Life Studies
Board on Agriculture and Natural Resources

Committee on a Review of the Citrus Greening Research and Development Efforts Supported by the Citrus Research and Development Foundation: Fighting a Ravaging Disease

Jacqueline Fletcher (chair)
Regents Professor Emerita
National Institute for Microbial Forensics and Food and Agricultural Biosecurity
Department of Entomology and Plant Pathology
Oklahoma State University

May R. Berenbaum*
Swanlund Chair of Entomology, and
Department of Entomology
University of Illinois

Stewart Gray
Senior Research Plant Pathologist
Agricultural Research Service
U.S. Department of Agriculture, and
Professor of Plant Pathology
Cornell University
Ithaca, N.Y.

Russell L. Groves
Vegetable Extension Specialist, and
Department of Entomology
University of Wisconsin

Ralph Scorza
Ralph Scorza LLC
Shepherdstown, W.Va.

Lindsay R. Triplett
Primary Investigator, and
Assistant Agricultural Scientist II
Jenkins-Waggoner Laboratory
Department of Plant Pathology and Ecology
Connecticut Agricultural Experiment Station
New Haven

John Trumble
Distinguished Professor
Department of Entomology
University of California

Bing Yang
Associate Professor
Department of Genetics, Development, and Cell Biology
Iowa State University


Camilla Y. Ables
Staff Officer

*Member, National Academy of Sciences