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 each new harvest seasons begins in the fall.
Around the world, black spot can be found in Argentina, Australia, Brazil, China, Ghana, Mozambique, the Philippines, South Africa, Sub-Saharan Africa, Taiwan, and Uruguay, among other humid subtropical countries.
It is likely to continue to spread slowly.
Citrus Black Spot
Caused by the fungus Phyllosticta citricarpa, also know as Guignardia citricarpa.
All commercial cultivars are susceptible, but late-maturing oranges (e.g., 'Valencia') and lemons are most vulnerable.
Affects fruit rind, twigs, 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.
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
Numerous small, slightly raised lesions that can be tan to brown
Occurs on green and mature fruit and does not have pycnidia
May become hard spot later in season
First appears on sunny side of fruit
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
The 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.
Rare in well-managed groves; most common on lemons
Can be seen on older leaves
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, synthetic fungicides)
Eliminate leaf litter
Increase airflow in trees
UF/IFAS Citrus Research and Education Center website www.crec.ifas.ufl.edu
Annual Florida Citrus Production Guide
Citrus Black Spot identification sheets
Citrus Black Spot Management Timing Schedule
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 UF/IFAS Extension office or the Florida Division of Plant Industry at 1-800-282-5153
UF/IFAS Citrus Research and Education Center
Extension Program Manager
Megan Dewdney, Ph.D.
UF/IFAS Department of Plant Pathology
Jeff Rollins, Ph.D.
UF/IFAS Indian River Research and Education Center
Mark Ritenour, Ph.D.
UF/IFAS Gulf Coast Research and Education Center
Natalia Peres, Ph.D.
UF/IFAS Southwest Florida Research and Education Center
Ozgur Batuman, Ph.D.
UF/ IFAS Extension Offices with Citrus Agents
Hardee, Hendry, Highlands, Lake, Polk, St. Lucie, Sumter
UF/IFAS Extension Citrus Agents: http://citrusagents.ifas.ufl.edu
UF/IFAS Citrus REC: http://www.crec.ifas.ufl.edu
UF/IFAS Southwest Florida REC: https://swfrec.ifas.ufl.edu/
Local UF/IFAS Extension Office: http://sfyl.ifas.ufl.edu/find-your-local-office/
For more information, please contact the UF/IFAS Citrus Research and Education Center, Lake Alfred 863-956-1151