Citrus Canker: An Established Infection in the Florida Citrus Industry1
Click here to view this publication as a brochure in PDF: https://edis.ifas.ufl.edu/pdffiles/CH/CH19900.pdf
Canker History
1910
First introduction into Florida
1933
Eradication of first introduction of canker was successful
1986
Second introduction into Florida on the Gulf coast
1994
Second introduction of canker was declared eradicated
1995
Third introduction into Florida in urban Miami area
2000
A statewide mandatory eradication using 1,900 foot rule was implemented
Quarantine areas were established when canker was detected
Mandatory statewide decontamination procedures began
2002
Removal of infected and exposed trees was delayed due to lawsuits from homeowners
2004–2005
The hurricanes magnified the spread of canker across the state
2005
First nursery infected with canker was found
2006
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
Biology
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!
Contacts
UF/IFAS Citrus Research and Education Center
Jamie Burrow
Extension Program Manager
863-956-8648
Megan Dewdney, Ph.D.
Plant Pathologist
863-956-8651
Lukasz Stelinski, Ph.D.
Entomologist
863-956-8851
Evan Johnson, Ph.D.
Plant Pathologist
863-956-8649
UF/IFAS Indian River Research and Education Center
Mark Ritenour, Ph.D.
Postharvest Physiologist
772-468-3922
UF/IFAS Southwest Florida Research and Education Center
Ozgur Batuman, Ph.D.
Plant Pathologist
239-658-3408
UF/IFAS Extension Offices with Citrus Agents
Hardee, Hendry, Highlands, Lake, Polk, St. Lucie, Sumter
Websites
UF/IFAS Extension Citrus Agents
http://citrusagents.ifas.ufl.edu
UF/IFAS Citrus REC
UF/IFAS Indian River REC
UF/IFAS Southwest Florida REC
Local UF/IFAS Extension Office