U.S. Department of Agriculture’s (USDA) officials have confirmed the first detection of sweet orange scab (SOS) in Alabama. The fruit sample was collected in Baldwin County by Alabama Department of Agriculture and Industries’ (ADAI) plant protection inspectors during a delimiting survey for citrus greening disease. The Auburn University Plant Diagnostic Clinic provided the initial diagnosis of SOS, and USDA Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) program lab personnel confirmed the diagnosis.
SOS is a plant disease caused by the fungus Elsinöe Australis and does not pose a threat to human or animal health. The disease is appropriately named as it results in scab-like lesions on fruit rinds and, less often, on leaves and twigs of sweet oranges, limes, lemons, mandarins, satsumas, kumquats, grapefruit, tangerines and tangerine hybrids. This is the first confirmed case of SOS in Alabama despite annual surveillance for citrus pathogens by ADAI plant protection inspectors.
The damage produced by SOS is superficial and does not affect internal fruit quality or taste. Infected fruit is likely to drop prematurely, and the scabby lesions reduce the fruit’s fresh market value. The initial scab will form during the early stages of fruit development, and is slightly raised and pink to light brown in color.
The pathogen requires moist conditions to reproduce and is spread primarily by splashing water. It is also spread by infected nursery stock, or on objects such as animals, clothing, or nursery/farm equipment.
The positive plant was found in a residential area approximately 10 miles north of the Gulf of Mexico in Lillian, Alabama. A delimiting survey will be conducted in January 2018 to determine if this is an isolated case. An announcement will be made prior to the survey to notify residents within the 1-mile radius of the SOS detection in which ADAI inspectors will be surveying citrus plants in the area. For questions concerning sweet orange scab, contact the ADAI Plant Protection Division at (334) 240-7225.
Images credit: Sweet orange fruit in Brazil/Permission granted by Dr. Megan Dewdney, associate professor of plant pathology at the UF/IFAS Citrus Research and Education Center.