HLB Management 

UF/IFAS HLB Research Outcomes: A Promise Delivered
UF/IFAS researchers have found more solutions for managing Huanglongbing (HLB or citrus greening) in the last 15 years than in the last 100 years before it was found in Florida.
With this science -based information, Florida citrus producers have a fighting chance to continue to be the nation’s largest producer of orange juice and a world leader in citrus research and development.
There are more than 100 ongoing HLB research projects in UF/IFAS that fall under one of the general areas of focus listed below.

Insect (psyllid) and Pathogen Control the Give Trees a Fighting Chance

• Research has led to psyllid management strategies that slow the spread of HLB
• 2019–2020 Florida Citrus Production Guide: Asian Citrus Psyllid
• The ABCs of Psyllid Management
• Presentation: Possible IPM Approaches to Pest Management under HLB
• Presentation: Making Sense of Spraying: Keeping Resistance in Check; and Accounting for Biological Control
• TAP Sampling for Asian Citrus Psyllid (ACP) Field Sheet

• Research has led to suppression of the Asian Citrus Psyllid and isolation of the CLas bacterium
• Presentation: Bt Toxins for Suppression of Asian Citrus Psyllid
• Presentation: Can RNA Interference Technology Contribute to Controlling Asian Citrus Psyllid
• Can RNA Interference Technology Contribute to Controlling Asian Citrus Psyllid

• New psyllid control programs are being developed that reduce pesticide use in favor of more environmentally friendly, sustainable solutions for pest management
• Viruses May Help Control ACP Population

• Field testing on numerous anti-bacterial products and plant-derived compounds are being conducted that eliminate the HLB – causing bacteria in the plant or reverse the plant damage to restore tree growth and productivity.

Breeding New Greening-Tolerant Trees

• Citrus growers are now planting new HLB-tolerant citrus varieties released by UF/IFAS that will live linger and produce better-quality fruit.
• Watch a video  about the UF/IFAS Citrus  breeding program click here

• Research has proven the importance of proper rootstock/scion combination when living with HLB.
• https://research.ifas.ufl.edu/media/researchifasufledu/docs/pdf/Citrus-2019.pdf

• New fruit varieties released by UF/IFAS have better juice quality and the potential to increase consumer demand for Florida orange juice.
• Top Picks from Citrus Variety Display Days
• Estimating Willingness to Pay for New Mandarin Cultivars: A Revealed Preference Approach
• Presentation:  Use of LB8-9 Sugar Belle® Juice in OJ Processing

• More than 1.5 million UF/IFAS-bred disease-tolerant trees planted in the last five years.
• An Update on UF/IFAS CREC Citrus Scion Varieties
• New Planting Options for Citrus Growers
• Florida Citrus Rootstock Selection Guide 4th Edition

• New citrus varieties developed using gene editing to remove genes responsible for disease symptoms are currently in field trials.
• Citrus Propagation
• Orange Opportunities
• What is Crispr and What Does it Mean for Citrus?

Integrated Grove Management Solutions

• UF/IFAS Research discovered that HLB severely impairs the ability of the citrus tree root system to take up water and nutrients, leading to new grove management practices that are now proving to keep trees alive and productive despite HLB. This also means that irrigation management is key.
• Dr. Evan Johnson talks about  root health in this article http://citrusindustry.net/2020/02/14/root-health-update/ and in the January 2020 All in for Citrus podcast  http://citrusindustry.net/allinforcitrus/
• Presentation: Structural Roots and HLB: Implications for Young Tree Management
• Studying Citrus Roots in the HLB Era
• Irrigation Management for Young Citrus Trees

• Research has shown that growers can improve root performance through proper soil pH management for maximum nutrient uptake by the root system 2 ½ years after soil acidification, yields in HLB-infected groves improved significantly.
• Root Health Management

• Research has led to improved nutrient management techniques like spoon feeding water and nutrients and frequent fertigation.
• Nutrition:  No One Size Fits All
• Spoon-Feeding Nutrition and Protecting New Flush for HLB
• HLB-Affected Citrus Response to Frequent Irrigation and Varied Fertilization in
• Summer Tree Care Practices to Improve Fruit Quality and Yield
• Fruit Drop of Citrus in Summer Months

• Research on growing citrus under protective screen (CUPS) has led to hundreds of acres of specialty fresh fruit varieties being planted and grown, revitalizing the Florida gift-fruit shipping segment of the citrus industry. Protective covers for new trees is another innovation.
• Citrus Under Protective Screen Production Systems
• Research Update: Citrus Under Protective Screen  
• Presentation: Growing Young Citrus Trees Under Individual Protective Covers (IPCs): What We Know After 18 Months [PDF]

Rootstock/Scion Selection 

UF/IFAS breeders have screened thousands of rootstock hybrids for HLB tolerance that could be transmitted to grafted scions. They have identified a few truly promising selections.  The combination of UF OLL-8 cultivar on UFR-4 rootstock has a strong performance for both yield and tree health.

For a list of  HLB tolerant varieties that have been developed by UF/IFAS breeders, Click Here.

When preparing for replanting, an important factor to consider is the choice of rootstock. Choosing the right rootstock and scion combination can result in higher economic returns without any additional cost. Rootstocks affect scion vigor, yield, fruit size, juice quality, and pest tolerance. However, tree growth, yield, and fruit quality interact strongly with climate, soil type, tree spacing, and other factors, often producing contradictory reports on rootstock performance in different areas.

Rootstock selection should be based on soil adaptability, soil pH, pest and disease pressure, desired tree spacing and size control, and other characteristics. Several new rootstock selections were recently released, but not much information exists on their long-term performance under different environmental conditions and different commercial management. Many of these new rootstocks are currently being evaluated under the Fast Track program and it is anticipated that new information will be available soon. Also important is the choice of scion to be used in combination with the selected rootstock. Several novel scion varieties have been released by the breeding programs at the USDA and the University of Florida. These novel varieties are expected to have better field performance (disease tolerance) and better fruit quality, making some of them suitable for the fresh fruit market.

2019–2020 Florida Citrus Production Guide: Rootstock and Scion Selection

Ute Albrecht, Fernando Alferez, and Mongi Zekri  Download here