University of FloridaSolutions for Your Life

Download PDF
Publication #CH198

Citrus Greening (Huanglongbing): A Serious Threat to the Florida Citrus Industry1

J.D. Burrow, T.M. Spann, M.E. Rogers, and M.M. Dewdney2

This publication was designed as a trifold brochure. Click here to view in brochure format (pdf, 375 KB)

Huanglongbing History

  • In 1995, the official name for greening became Huanglongbing (HLB)

  • The vector, Asian citrus psyllid, was first found in Florida in 1998

  • Citrus greening was first detected in residential areas in South Florida in August 2005

  • As of October 2006, HLB infected trees had been found in twelve counties

  • By October 2007, infected trees had been discovered in twenty-eight counties

  • Thirty-two counties had confirmed greening in their area by the end of 2008

  • By February 2010, thirty-four counties had at least one positive confirmed greening infected tree

  • HLB is now confirmed in all commercial citrus growing counties in Florida

  • Currently, identified in most non-commercial citrus growing counties in residential properties

Huanglongbing Biology

  • A disease caused by a phloem-limited bacterium affecting all citrus cultivars

  • The rod-shaped, gram negative bacterium is named Candidatus Liberibacter asiaticus

  • Bacterium does not move between trees without the insect vector or through grafting

  • The bacteria are present in symptomatic tissues in low numbers

  • Phloem tissue is damaged when bacteria are present

  • Starch accumulates to toxic levels in plant cells

  • Excessive phloem tissue is produced in infected trees

  • Bacteria are at their highest levels in young asymptomatic tissues and appear to die as tissues age and become symptomatic

  • Changes to the plant tissue begin in the early infection before symptoms

Varieties Affected

  • All citrus varieties and rootstocks can be affected by citrus greening

  • Affects plants in the Rutaceae family (ex. box orange and orange jasmine)

Greening Vector

  • Asian citrus psyllid (Diaphorina citri)

  • Five nymphal stages

  • Numerous generations per year

  • Egg to adult in 2 weeks at 75°F to 85°F

  • Egg stage lasts an average of 3 to 4 days

  • Duration of the nymphal stages is about 12 to 14 days at 82°F

  • Adult psyllids may live for several months in cool temperatures

  • Psyllids can acquire the bacterium from infected trees, regardless of whether symptoms are present on the tree

  • The longer psyllids remain uncontrolled and are allowed to feed on infected trees, the higher the chance that those psyllids will acquire and spread greening to other trees

  • Psyllid populations are best managed by controlling adults prior to the presence of new flush which facilitates rapid population growth

  • Chemical control of the psyllid and removal of infected trees are the only methods currently available to manage the spread of greening

Commercial Management

Residential Management

  • Remove infected trees

  • Use of disease-free nursery trees (a certified nursery tag should be attached to tree at time of purchase)

  • Use horticultural oil sprays or soil applied insecticides (active ingredient: imidacloprid) to manage psyllid populations

  • When applying pesticides, remember the label is the law

Greening Symptoms

  • Symptoms can be found year round, but are more prominent September through March

Figure 4. 

Vein corking

[Click thumbnail to enlarge.]

Figure 5. 

Fruit remain green at the blossom end

[Click thumbnail to enlarge.]

Figure 6. 

Yellow Shoots

[Click thumbnail to enlarge.]

Figure 7. 

Yellow veins

[Click thumbnail to enlarge.]

Figure 8. 

Reduced fruit size

[Click thumbnail to enlarge.]

Figure 9. 

Blotchy mottle—key diagnostic symptom

[Click thumbnail to enlarge.]


  • Citrus Research and Education Center website:

  • Greening Symptoms Laminated Sheet

  • Greening Symptoms versus Nutritional Deficiencies Laminated Sheet

  • Greening Symptoms versus Blight and Tristeza Laminated Sheet

  • Greening Field ID Pocket Guide

  • Greening Training DVD

  • Greening Screensaver

  • 2008 Florida Citrus Pest Management Guide

Southern Gardens Diagnostic Laboratory

111 Ponce de Leon Ave., Clewiston, FL 33440
(863) 902-2249
Contact: Mike Irey

UF/IFAS Southwest Florida REC

2685 SR 29 N., Immokalee, FL 34142
(239) 658-3400

Florida Division of Plant Industry

PO Box 147100, Gainesville, FL 32614-7100
(800) 282-5153

UF Plant Diagnostic Center

Building 1291, 2570 Hull Rd. Gainesville, FL 32611

Before sending samples, contact the testing facility to obtain proper sampling procedures, submission guidelines, and fees.


UF/IFAS Citrus Research and Education Center

Jamie Burrow
Canker & Greening Extension Education
Megan Dewdney, Ph.D.
Plant Pathologist
Jim Graham, Ph.D.
Soil Mircobiologist
Michael Rogers, Ph.D.

UF/IFAS Southwest Florida Research and Education Center

Pamela Roberts, Ph.D.
Plant Pathologist
Phil Stansly, Ph.D.
Bob Rouse, Ph.D.

UF/ IFAS Extension Offices with Citrus Agents

Hardee, Hendry, Highlands, Lake, Polk, St. Lucie, Sumter


UF/IFAS Extension Citrus Agents
UF/IFAS Southwest Florida REC
Local UF/IFAS Extension Office

For more information, please contact the UF/IFAS Citrus Research and Education Center, Lake Alfred 863-956-1151



This document is CH198, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date July 2008 (authored by Burrow, Spann*, Rogers). Revised March 2014. Visit the EDIS website at


J.D. Burrow, coordinator for canker and greening extension education, M.E. Rogers, associate professor, Entomology Department and M.M. Dewdney, assistant professor, Plant Pathology Department, Citrus Research and Education Center, Lake Alfred, FL, 33850, UF/IFAS Extension.

*T.M. Spann, former associate professor, Horticultural Sciences Department

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.