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Coordinated Response to Citrus Greening Disease

Huanglongbing (HLB), also known as citrus greening disease, is one of the most serious citrus diseases in the world. While the disease, or its vector, has impacted all citrus growing regions of the United States, it has had significant impact on commercial citrus growing regions of Florida and Texas. Moreover, the pathogen is poised to expand from residential areas of California to threaten commercial production.

HLB Multi-Agency Coordination (MAC) Group

In December 2013, the United States Department of Agriculture (USDA) implemented a unified emergency response framework, the HLB MAC group, to better position the Department to help address the citrus industry’s immediate and long-term needs in dealing with this disease. In addition to USDA’s Animal and Plant Health Inspection Service (APHIS), the MAC is comprised of representatives from USDA’s Agricultural Research Service (ARS), and National Institute of Food and Agriculture (NIFA), the United States Environmental Protection Agency, State departments of agriculture in Arizona, California, Florida, and Texas, and citrus industry organizations in California, Florida, and Texas. The HLB MAC Group helps to coordinate and prioritize Federally funded research with industry's efforts to bridge the gap between research and implementation, reduce unnecessary duplication, and more quickly provide practical tools for citrus growers to use.

Specifically, the HLB MAC Group:

  • Coordinates funding across Federal and State agencies, universities, and private companies to maximize investments, reduce duplication, and focus research on the most promising ideas.
  • Funds projects most likely to deliver effective and practical tools to growers.
  • Combines successful project results into holistic and sustainable solutions.
  • Involves growers in the field evaluation of new methods and treatments to identify management strategies.
  • Maintains sense of urgency in the research community, driving them to find near-term solutions.

Since 2014, Congress has appropriated $64 million in funding to APHIS in support of HLB MAC goals to speed the development of tools to help the citrus industry fight back against HLB in the United States. Projects have focused on six critical areas: Asian citrus psyllid (ACP) control, infected tree therapies, technologies to protect new plantings against HLB infection, early detection technologies, management practices to maintain productivity, and HLB-tolerant citrus varieties.

HLB MAC-funded projects have:

  • Expanded production capacity for ACP biological control agent Tamarixia radiata in California.
  • 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.
  • Developed and released training methods to teach canines to detect ACP and HLB in commercial and residential settings.
  • Helped move HLB detector dogs to market in California.
  • Developed planting designs that reduce ACP pressure and produce healthier trees and better fruit with reduced water and herbicide use.
  • Developed an ACP attract and kill device that can reduce ACP intensity by over 60 percent.
  • 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 refuting claims that adding microbial cocktails to grove soil would improve tree growth.
  • Field tested two antimicrobial treatments that Florida has implemented to: reduce bacterial stress on infected trees; stabilize/restore productivity and extend productive life of infected trees; help new plantings transition to full production; reduce fruit drop, improve fruit quality, and stabilize fruit production.
  • Developed harmonized methodology for evaluating greenhouse and field trials to combat HLB across growing areas and regions.
  • 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.

HLB MAC-Funded Projects:

FY 2023 list of funded projects (PDF, 162 KB)

FY 2022 list of funded projects (PDF, 152 KB)

FY 2021 list of funded projects (PDF, 225 KB)

FY 2020 list of funded projects (PDF, 135 KB)

FY 2019 list of funded projects (PDF, 157 KB)

FY 2018 list of funded projects (PDF, 181 KB)

Citrus greening project lists

Animal and Plant Health Inspection Service

Citrus Research and Development Foundation

Citrus Research Board

National Institute of Food and Agriculture

Recent Activities

As with all good science, the HLB MAC group embraces an iterative process building upon small successes by exploring interactions among methods and environments, while evaluating the impact of scale. To determine the best management practices and methodologies for producing citrus under the threat and pressure of HLB, in 2019 and 2020, APHIS provided HLB MAC funds towards the Florida Citrus Research and Field Trials (CRaFT) project to conduct field evaluations of strategies that showed previous scientific evidence of success in combating citrus greening. This project brought in growers, as collaborators, to evaluate interactions between methods, treatments, environments, rootstock/scion combinations, and growing practices.

In 2021, building on the success of the CRaFT approach in Florida, APHIS initiated similar projects in California and Texas. As these states represent different stages of disease progression yet share the common goal of robust healthy trees and a productive industry, this approach offers a window to evaluate the impact of tools available for all challenges that HLB poses in different environmental conditions. The results of these CRaFT-like projects will benefit all citrus-growing regions in the United States that are threatened by this devastating disease. APHIS will continue to support CRaFT-like projects in these states in 2022.

Contact the HLB MAC Group

Contact the Chair of the HLB MAC Group for more information.

Sign Up for HLB MAC Updates

To receive updates on the HLB MAC Group's activities, 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.