Superman’s comic hero ability to stop a locomotive and leap tall buildings in a single bound are traits needed by the Arizona citrus industry to control pest and disease threats including the latest villain – sweet orange scab (SOS).

SOS is a fungal disease of citrus found in different citrus varieties and caused by Elsinoë australis. The result is scab-like lesions on the fruit rind and occasionally on leaves and twigs.

The Arizona Department of Agriculture (ADA) conducted public meetings in early March in Phoenix and Yuma on citrus pest and disease threats. State and federal plant pest regulators discussed the latest developments on SOS, the Asian citrus psyllid (ACP), and citrus greening (Huanglongbing disease or HLB).

“A (SOS) quarantine is coming to Arizona,” Jerald Levitt told the crowd at the Yuma Agricultural Center. Leavitt is the USDA Animal and Plant Health Inspection Service (APHIS) state plant health director for Arizona. APHIS planned to enact the statewide SOS quarantine in mid-March.

The good news is the APHIS quarantine comes at the end of Arizona’s 2010-2011 citrus season. The two citrus sectors likely to be effected the most by the APHIS regulations are packinghouses and plant nurseries. Packinghouse regulations will mostly take root this fall when the next harvest begins.

As of mid March, the APHIS laboratory in Beltsville, Md., had confirmed 10 positive finds of SOS in Arizona through DNA testing.

The Arizona SOS finds include two in commercial lemons in Yuma County, according to Gary Russell of APHIS in Phoenix, Ariz. Five positive SOS cases were found in Mesa in Maricopa County (central Arizona) including three in sweet orange and one each in tangelo and mixed citrus (four commercial finds).  Two of the three finds in nearby Queen Creek were in commercial citrus. All non-commercial finds were in residential citrus.

“This is another in a series of problems for the citrus industry in Arizona,” said Mark Spencer, citrus grower, packer, and partner with Associated Citrus Packers, Inc. in Yuma, Ariz.

“We must continue to be resilient. It doesn’t sound like sweet orange scab will be the one (problem) to put us away all together.”

According to APHIS, infected fruit can drop prematurely. The disease can stunt young citrus seedlings. SOS is spread slowly by microscopic fungal spores produced in the scabs. Trees are more susceptible to infection with new shoot growth and when petals begin to fall. As the growing tissue matures, it becomes less susceptible.

Spores can spread the disease to susceptible plants with sufficient moisture in the environment. The fungus can live through the winter in the tree canopy on limbs and on fruit infected during the previous season. Symptoms of the disease can be visually detected year around. The disease produces symptoms within a week.