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Multi-Agency Response to Devastating Citrus Disease

Huanglongbing (HLB), also known as citrus greening disease, is one of the most serious citrus diseases in the world. It poses a very real and growing threat to citrus production in the United States. In response to industry concerns, USDA established a unified emergency response framework to better position the Department to respond in a more agile, concerted, and direct way to both the immediate and long-term needs of the citrus industry.

HLB Multi-Agency Coordination (MAC) System

Participating organizations include USDA's Animal and Plant Health Inspection Service (APHIS), Agricultural Research Service (ARS), and National Institute of Food and Agriculture (NIFA), the U.S. Environmental Protection Agency, as well as State departments of agriculture and industry groups. These partners have formed an HLB Multi-Agency Coordination (MAC) Group—or HLB MAC Group—to jointly establish research priorities, coordinate activities, and collect, analyze, and disseminate information. The HLB MAC Group helps to coordinate and prioritize Federal research with industry's efforts to complement and fill research gaps, reduce unnecessary duplication, speed progress, and more quickly provide practical tools for citrus growers to use.

The HLB MAC provides industry with a single Federal point of contact for all Federal and State entities that work on citrus issues. In addition, the framework maintains and shares a common operating picture of HLB response that is accessible across jurisdictions and functional agencies. This common operating picture greatly improves strategy development, policymaking, and resource allocation—ensuring funds are invested where they can have maximum impact based on input of all participants.

Specifically, the HLB MAC:

  • Coordinates funding across Federal and State agencies, universities, and private companies to maximize investments, reduce duplication, and focus research on the most promising ideas.
  • Rapidly funds projects most likely to deliver effective and practical tools to growers.
  • Combines successful project results into holistic and sustainable solutions.
  • Helps move field-tested tools into commercialization.
  • Maintains sense of urgency in the research community, driving them to find near-term solutions.

HLB MAC-Funded Projects

Since 2013, the HLB MAC has invested nearly $47 million to speed the development of tools that could help the U.S. citrus industry fight back against HLB. Projects have focused on four critical areas: Asian citrus psyllid (ACP) control, infected tree therapies, technologies to protect new plantings against HLB infection, and early detection technologies.

HLB MAC-funded projects have:

  • Tripled the production and release ACP-killing wasps, from 4 million to 12 million per year. These wasps have reduced ACP populations by more than 50 percent in Texas and as much as 99 percent around California release sites.
  • Removed nearly 6,000 acres of abandoned groves in Florida, eliminating uncontrolled ACP habitat and prompting state legislation to incentivize further removal of abandoned groves.
  • Trained and field tested canines to detect HLB in commercial and residential settings.
  • Applied thermotherapy to more than 3 million HLB-infected trees in Florida to extend trees’ productive life by promoting new growth and slowing the progress of the disease.
  • Helped move thermotherapy technology to market by delivering a prototype machine to growers who used the design to build their own machines and private companies who improved the technology and now offer thermotherapy services.
  • Developed soil acidification technology that could be used on a broad scale to lower the pH of infected tree roots, helping to improve overall tree health and production.
  • Saved growers from investing in ineffective technologies by researching and disproving claims that adding microbials to grove soil would improve tree growth.
  • Field tested two antimicrobial treatments to improve the overall health and quality of infected trees. That data was used by Florida to obtain a Section 18 exemption from the Environmental Protection Agency, allowing them to use antimicrobials on an emergency basis.
  • Initiated a rapid propagation project to accelerate field testing of 35 varieties of HLB-tolerant mandarin and sweet orange trees, which will make them available 2 years earlier than traditional propagation practices.

View the FY2019 list of funded projects (PDF, 214 KB).

View the FY2019 project summaries (PDF, 1.3 MB).

Submit a Project Suggestion

Interested stakeholders are invited to submit project suggestions three times a year (by November 1*, February 1, and June 1) as resources are available. Specifically, the HLB MAC is seeking projects that have the greatest potential to deliver a near-term positive impact for citrus producers. All project suggestions must be no more than 24 months in duration and address one of the goal areas described below.

*The November 1, 2019, suggestion period is postponed until Congress passes the fiscal year 2020 budget.

HLB MAC Goal Areas

  1. Keeping HLB Out Of Citrus. This goal seeks to prevent disease in citrus orchards that are currently free from HLB.
    • Vector management (e.g., chemical or semiochemical ready for field level testing, tools for trapping in the field, or substances that repel the Asian citrus psyllid)
      • Insect vector detection and monitoring
      • Reducing insect vector populations, reproduction, and/or movement
      • Preventing disease transmission within citrus (blocking uptake, dispersal
    • Pre-symptomatic detection of HLB (e.g., upscaling early detection methods into tools that can be used in the field for management or in the lab for high throughput diagnostics) for the purpose of:
      • Removing trees as they become infected
      • Identifying reservoirs of Candidatus Liberibacter asiaticus (CLas) outside of orchards
      • Identifying insect vectors that contain CLas
    • Resistance (e.g. trees that are unable to be infected)
      • Insect nymph cannot feed on the tree
      • Insect cannot transmit to tree during feeding
      • CLas cannot survive within or be transmitted by the tree
  2. Producing Citrus Under High HLB Disease Pressure. This goal seeks to mitigate the impact of HLB on citrus production.
    • Therapies to sustain production in diseased plants (e.g., therapies that can help diseased trees maintain productivity, or reduce or eliminate CLas in trees to lessen production impacts) with an emphasis on:
      • Multi-season production (yield and quality)
      • Fruit commercial utilization
    • Protect new plantings in the presence of disease and insect vector (e.g., methods, technologies, or tools that will protect new trees from infection or the impact of HLB; or a system of best horticultural practices that allows establishment and production of new orchards in the presence of high disease pressure) with an emphasis on:
      • New plantings reaching production without infection or without impact (assuming clean nursery stock is planted)
      • Strategies to reduce juvenile period, intensify production, and restore profitability even if the orchard replanting cycles are short or require increased capital investment
    • Tolerance (e.g., field testing trees that have reduced impacts on fruit production due to HLB infection)
      • Low CLas titer and corresponding lower impact on fruit drop/yield and quality
      • High CLas titer but low impact on fruit drop/yield and quality
  3. Remediation. This goal seeks ways to remediate the impact of HLB.
    • Inoculum management (e.g., non-destructive strategies for reducing the number of infected trees, especially those that are in the urban landscape or in abandoned or largely unmanaged groves)
      • Eliminating CLas from infected trees
      • Preventing CLas transmission
    • Insect vector eradication (e.g., areawide control or biocontrol)

Criteria for Evaluating Project Suggestions

The HLB MAC will carefully consider all project suggestions against the following evaluation criteria:

  • Positive Impact: The extent to which the proposed technology or solution is ready for field testing, will effectively manage HLB, and deliver positive impacts and tangible tools and solutions to the citrus industry within a reasonable period of time.
  • Utility: The extent to which producers and other industry members support the proposed tool or solution and find it practical, affordable, easy to use, and easy to incorporate into an integrated system for managing HLB.
  • Likelihood of Commercialization: The extent to which the proposed technology can be easily scaled up or commercialized within a reasonable amount of time (i.e., the delivery system is significantly improved and adaptable, there is a commercial partner that is ready and able to invest in the proposal and make the methods or technology readily available to growers).
  • Feasibility: The extent to which the proposed project will meet its design objectives and performance targets because it has appropriate milestones, clearly defined objectives, and access to adequate resources that are commensurate with the scope of work being described.
  • Technical Merit/Potential for Success: The extent to which the proposed project is using tools and employing methodologies that are known to be effective in addressing the problem, and that the group carrying out the actions is known to be reliable, experienced, and efficient in conducting such a set of actions.
  • Adaptability: The extent to which the proposed tools or actions will be broadly applicable over time to different soils, climates, conditions and are compatible with other HLB management activities in different citrus producing states.

Instructions for Submitting a Suggestion

To submit a project for consideration, please complete the suggestion template (PDF, 100 KB) and email it to

Contact the HLB MAC Group

Contact a member of the Multi-Agency Coordination (MAC) Group for more information.

Sign Up for HLB MAC Updates

If you would like to receive timely updates on the HLB MAC Group's activities, we invite you to join the APHIS Stakeholder Registry. Once you sign up, you can subscribe to the "Citrus Pests and Disease" topic through the following steps:

  1. Select Plant Health Information.
  2. Select Plant Health in the US (Domestic).
  3. Select Pest Management.
  4. Check the Citrus Pests and Disease box.
  5. Submit your subscription.