Citrus canker is a serious disease of citrus trees that was recently confirmed for the first time in southern Santa Rosa County. Because of questions I’m getting from the public, I’d like to share the following article written by Blake Thaxton and Mary Derrick, with University of Florida, Institute of Food and Agricultural Sciences Extension office in Santa Rosa County, and Mikaela Anderson, with the Florida Department of Agriculture and Consumer Services Division of Plant Industry.
Canker is caused by the bacterial pathogen Xanthomonas citri subsp. citri. Citrus canker has been a major pest in south and central Florida. It is economically damaging to the citrus industry and is also problematic to homeowners because it causes premature fruit drop and discolored fruit. Eventually infected trees become unproductive.
Canker was first introduced in 1912 into Florida and was declared eradicated in 1933. The disease was found again in the Tampa area in 1986. It was declared eradicated in 1994, but once again was found in 1995 in Miami. This time, the disease was not successfully eradicated, in part because hurricanes made the disease too widespread to control.
Despite its prevalence in south and central Florida, this disease has not been known in the Panhandle. The University of Florida and FDACS/DPI will be assessing the extent of the disease in Santa Rosa County.
How might you know if your citrus is infected by canker? One of the best indicators of canker is the presence of lesions, diseased spots, on the upper and lower surfaces of the leaves. The lesions are raised and have a rough surface and are surrounded by yellow halos. Similar lesions may be present on the fruit and stems as well.
If you suspect that your trees may have citrus canker, contact the DPI helpline at 1-888-397-1517 before taking any action, to reduce accidental spread of this disease.
Canker is highly contagious to citrus only and spreads rapidly due to wind, rain its presence on people's hands, clothes and tools.
Do not transport plant material that shows canker symptoms. Decontamination practices should be used when going from one citrus tree to the next. Hand washing with soap and water for 20 seconds or more to eliminate bacterium on the skin should be practiced, as well as using alcohol-based hand sanitizer. Pruning tools that come into contact with citrus should be disinfected by a fresh solution of one ounce of household bleach to one gallon of water.
Do not move a plant infected with citrus canker. Please call your local extension office for further instructions.
Larry Williams is an agent at the University of Florida's Institute of Food and Agricultural Sciences Extension office in Crestview.