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.
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.