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Citrus Canker: An Established Infection in the Florida Citrus Industry1

J. D. Burrow and M. M. Dewdney 2

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Canker History


First introduction into Florida


Eradication of first introduction of canker was successful


Second introduction into Florida on the Gulf coast


Second introduction of canker was declared eradicated


Third introduction into Florida in urban Miami area


A statewide mandatory eradication using 1,900 foot rule was implemented

Quarantine areas were established when canker was detected

Mandatory statewide decontamination procedures began


Removal of infected and exposed trees was delayed due to lawsuits from homeowners


The hurricanes magnified the spread of canker across the state


First nursery infected with canker was found


Mandatory eradication ended

2007 to present

Located in the majority of Florida counties

The removal of infected trees is now voluntary

Decontamination procedures are required statewide in commercial groves to prevent the spread of citrus canker


  • Bacteria is caused by Xanthomonas citri subsp. citri

  • Gram negative bacterium

  • Small (cannot be seen by the naked eye)

  • 1–3 microns in size

  • Rod-shaped cell covered with slime

  • Single polar flagellum

  • Survives in moist conditions

Varieties Affected

  • Highly susceptible varieties: grapefruit, lemons, navel, some early oranges (ex. Early Gold)

  • Less susceptible: Hamlins, tangelos

  • More tolerant: tangerines, hybrids (ex. Murcott), Valencia

Canker Spread

  • Wind-driven rain and storm events such as tornadoes and tropical storms

  • Overhead irrigation

  • Human movement of infected plant material

  • Human and equipment movement within groves

  • Citrus leafminer

  • Birds and other animals

  • Canker does not harm humans

Citrus canker is highly infectious!

Canker Symptoms

Leaf Symptoms

  • Early symptoms appear as slightly raised, tiny blister-like lesions

  • As lesions age, they turn tan to brown and a water soaked margin appears surrounded by a yellow ring or halo

  • Center of the lesion becomes raised and corky

  • Lesions are usually visible on both sides of a leaf

Stem and Fruit Symptoms

  • Older stem lesions are dark brown or black, raised, corky lesions surrounded by an oily or water-soaked margin

  • Mature lesions appear scabby or corky

  • Fruit lesions are dark brown to black, raised, often surrounded by yellow halos

  • Fruit lesions can cause blemishes and early fruit drop

Commercial Management

  • Decontamination of equipment and personnel

  • Windbreaks

  • Copper sprays

  • Stimulate natural defense in young trees

  • Leafminer control

  • Defoliation

  • Tree removal

Residential Management

  • Apply copper every three weeks mid-May to mid-July

  • Decontaminate lawn tools using one (1) ounce of bleach to one (1) gallon of water. (Do not store bleach-water solution as it will lose effectiveness within 24 hours.)

  • Prune infected area, double bag infected limbs, and discard in yard waste or

  • Burn infected plant material

  • Apply horticultural oil to lower leafminer populations

  • Do not transport infected plant material!


UF/IFAS Citrus Research and Education Center

Jamie Burrow
Extension Program Manager


Megan Dewdney, Ph.D.
Plant Pathologist


Lukasz Stelinski, Ph.D.


Evan Johnson, Ph.D.
Plant Pathologist


UF/IFAS Indian River Research and Education Center

Mark Ritenour, Ph.D.
Postharvest Physiologist


UF/IFAS Southwest Florida Research and Education Center

Ozgur Batuman, Ph.D.
Plant Pathologist


UF/IFAS Extension Offices with Citrus Agents

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


UF/IFAS Extension Citrus Agents


UF/IFAS Indian River REC

UF/IFAS Southwest Florida REC

Local UF/IFAS Extension Office


1. This document is CH199, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date July 2008. Revised March 2014 and May 2018. Visit the EDIS website at
2. J. D. Burrow, Extension program manager; and M. M. Dewdney, associate professor, Plant Pathology Department, UF/IFAS Citrus Research and Education Center, Lake Alfred, FL 33850.

Publication #CH199

Date: 4/28/2019

    Fact Sheet


    • Jamie Burrow