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Publication #PP281

Citrus Black Spot: No Longer an Exotic Disease... A manageable disease in the Florida Citrus Industry1

Megan Dewdney and Jamie Burrow2


  • Citrus black spot was first found in Southwest Florida in March 2010.

  • The initial find was contained to a small area centered in South Florida near Immokalee. By the first week of May, the disease had been found in another location about 14 miles from the original find.

  • It is expected to be found in additional areas when the new harvest seasons begins in the fall.

  • Around the world, black spot can be found in Argentina, Australia, Brazil, China, Ghana, Mozambique, Philippines, South Africa, Sub-Saharan Africa, Taiwan, and Uruguay, among other subtropical countries.

Citrus Black Spot

  • Caused by Guignardia citricarpa (sexual stage) and Phyllosticta citricarpa (asexual stage)

  • All commercial cultivars are susceptible, but late-maturing oranges (e.g., ‘Valencia’) and lemons are most vulnerable.

  • Affects fruit rind and leaves

  • Four main fruit symptom types: hard spot, false melanose, cracked spot, and early virulent spot

  • Most common symptom is hard spot

  • Causes fruit drop

  • Severely affected fruit can drop before harvest, causing significant yield loss.

Hard Spot

  • Small, round, sunken lesions with tan centers and brick-red to chocolate-brown margins

  • Fungal structures appear as slightly elevated black dots.

  • First appears on sunny side of fruit

False Melanose

  • Numerous small, slightly raised lesions that can be tan to brown

  • Occurs on green fruit and does not have pycnidia

  • May become hard spot later in season

  • First appears on sunny side of fruit

Cracked Spot

  • Large, flat, dark-brown lesions with raised cracks in their surface

  • Thought to be caused by an interaction with rust mite

  • Can become hard spot later in the season

  • Occurs on green and mature fruit

Early Virulent Spot

  • Also known as freckle spot

  • Small, reddish, irregularly shaped lesions

  • Occurs mostly on mature fruit as well as postharvest in storage

  • Can develop into either virulent spot or hard spot

  • Virulent spot is caused by the expansion and/or fusion of other lesions, covering most of the fruit surface toward the end of the season or in storage.


  • Wind-borne spores (ascospores and conidia), rain splash, or movement of infected plant material

  • Major source of inoculum is airborne ascospores (sexual spores) from the leaf litter.

  • Minor source of inoculum is conidia (asexual spores) from pycnidia that form on fruit, dead twigs, and leaf litter. The conidia are rain-splash dispersed. Potential problems on cultivars that have young and mature fruit on the tree simultaneously.

Figure 6. 

Reprinted by permission from Timmer, L. W., and Duncan, L. W. 1999. Citrus Health Management. American Phytopathological Society, St. Paul, MN.

[Click thumbnail to enlarge.]

Leaf Symptoms

  • Rare in well-managed groves; most common on lemons

  • Older lesions are small, round, and sunken with a gray center, dark-brown margin, and yellow halo.

  • Younger lesions are reddish brown with light centers and a diffuse yellow halo.


  • Apply fungicides (e.g., copper)

  • Eliminate leaf litter

  • Increase airflow in trees

Grower Resources

• UF/IFAS Citrus Research and Education Center website

  • Annual Florida Citrus Pest Management Guide

  • Citrus Black Spot laminated sheet

  • Citrus Black Spot Management Timing Schedule laminated sheet

  • Packinghouse Citrus Black Spot ID

  • Identification of Early Citrus Black Spot Symptoms

  • Citrus Black Spot Field Identification Pocket Guide

Report Likely Suspects

If you suspect your citrus tree may have this disease, please contact your local county extension office or the Florida Division of Plant Industry at 1-800-282-5153


UF/IFAS Citrus Research and Education Center

Jamie Burrow2
Canker & Greening Extension Education


Megan Dewdney, Ph.D.2

Plant Pathologist


UF/IFAS Southwest Florida Research and Education Center

Pamela Roberts, Ph.D.
Plant Pathologist


Indian River Research and Education Center

Mark Ritenour, Ph.D.
Postharvest Physiology


Gulf Coast Research and Education Center

Natalia Peres, 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 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 PP281, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date February 2011. Revised January 2014. Visit the EDIS website at


Megan Dewdney, assistant professor, Department of Plant Pathology, and Jamie Burrow, coordinator, Canker, HLB and Exotic Disease Extension Education, Citrus REC, Lake Alfred, Florida; UF/IFAS Extension; Gainesville, FL 32611.

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.