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ALERT: Citrus Canker Confirmed in Georgia

On June 14th, 2022, the Georgia Department of Agriculture (GDA) announced that citrus canker has been confirmed within a commercial citrus grove in Decatur County, Georgia. This bacterial disease, which is subject to USDA-APHIS quarantine regulations, is widespread within Florida, and has also been found previously in Louisiana (2014), Texas (2016), Alabama (2021), and in a South Carolina nursery (2022).

Leaves with potential citrus canker symptoms (Figure 1) were first identified on May 17th, 2022, and leaf samples were initially tested at both a University of Florida laboratory and at the University of Georgia Plant Disease Clinic in Athens, Georgia. Positive samples were then forwarded to USDA-APHIS for official confirmation of the presence of the citrus canker bacterium in the symptomatic plant tissue. According to the GDA announcement, official confirmation of citrus canker was received from the USDA-APHIS Plant Protection and Quarantine (PPQ) laboratory late last week.

As federal guidelines require surveys to determine the extent of citrus canker establishment in the state, GDA and USDA-APHIS PPQ personnel have begun conducting a survey for citrus canker infected trees in the area of Georgia where it was first confirmed.

Figure 1. Citrus Canker Lesions on Grapefruit Leaf from Decatur County, Georgia (Picture by Brian Hayes – UGA Cooperative Extension)

Citrus canker is caused by the bacterial plant pathogen Xanthomonas axonopodis pv. citri (Xac). While this bacterial pathogen is not harmful to humans, pets, or other animals, it can cause lesions on the leaves, stems, and fruit of nearly all types of citrus. This pathogen can be spread easily from tree-to-tree by wind-driven rain (including tropical storms and hurricanes), overhead irrigation, human movement of infected plant material, movement of contaminated equipment within and between groves, and by movement of humans, birds, and other animals. In particular, the citrus leafminer – a very common insect pest of citrus – can create openings that allow for infection with the citrus canker bacterium.

Due to the potential for citrus canker to spread between infected trees and groves, Georgia citrus growers (both commercial and residential) are strongly encouraged to scout their trees for any signs of citrus canker. If canker is suspected, growers should contact their local University of Georgia Extension Agent for more information about citrus canker diagnosis and testing.

More information about the signs and symptoms of citrus canker can be found here.

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About Jonathan Oliver

Dr. Jonathan Oliver is an Assistant Professor and Extension Specialist in the Department of Plant Pathology at the University of Georgia. He has a 75% research and 25% extension appointment. Dr. Oliver started in his current position at the University of Georgia in mid-2017 as an extension fruit pathologist at the Coastal Plains Experiment Station in Tifton, Georgia. His responsibilities include research and extension activities focused on pathogen biology and disease management in fruit crops grown primarily in the southern part of Georgia, including blueberries, blackberries, citrus, and other emerging fruit crops. Dr. Oliver obtained a BS degree in Plant Pathology and Microbiology & Cell Science from the University of Florida in 2005, and a PhD in Plant Microbe Biology from Cornell University, New York State Agricultural Experiment Station in Geneva, NY in 2011. In addition, he has also been postdoctoral researcher at Kansas State University and Auburn University. At Auburn, he characterized the interactions between the emerging bacterial pathogen, Xylella fastidiosa, and its blueberry plant hosts. He currently serves as a Plant Pathology Section editor for the Southeast Regional Blueberry Integrated Management Guide.