Be Alert for Citrus Canker in Alabama

Alabama Cooperative Extension implores growers to be on the lookout for symptoms of citrus canker disease in their trees. Commercial growers need to scout their trees regularly to stop the disease’s potential spread, says Kassie Conner, Alabama Extension specialist.

“What we need people to do right now is look for these symptoms and report it if they find it,” Conner said.

SYMPTOMS AND SUSCEPTIBILITY
Citrus canker symptoms include leaf spots. Bright yellow halos are observed around raised spots.

Fruit symptoms are similar to the leaf symptoms. Fruit spots grow and widen during the season. Fruit that has been impacted significantly can drop prematurely, leading to reduced yields.

All aboveground tissue is susceptible to citrus canker.

Grapefruit are most susceptible to citrus canker, while mandarins are most resilient. This is important for Alabama and Georgia, since satsumas are mostly grown in those two states. However, when there are wounds in the plant tissue, susceptibility becomes a non-factor. It will allow for the entry of the bacteria into those wounds.

QUARANTINES COMING
Citrus canker was detected in Mobile and Baldwin counties along the Gulf Coast in 2021. Conner said the Alabama Department of Agriculture and Industries is in the process of deciding if quarantining should be isolated to those two counties or include the whole state.

“Citrus canker can spread so quickly; they’re afraid they’re not going to be able to get in front of it,” Conner said.

All of Florida as well as parts of Louisiana and Texas are already quarantined for the disease.

PROTECTIVE MEASURES
Curative management is not an option. Trees with citrus canker must be removed. The best protection is infection prevention.

“For commercial growers, this includes sanitation, windbreaks, copper applications and leafminer control,” Conner said.

Planting tall plants as windbreaks around the perimeter of a grove can slow the wind speed down to less than 18 miles per hour. Copper applications are protectant fungicides or bactericides that are applied every 21 days. For example, in Florida, this means applications in mid-April, early-to-mid-May or late May and early June. Growers can apply 0.5 to 1 pound in dry weather or 1 pound in wet weather.

Leafminers don’t spread the disease, but they open wounds that allow bacteria to enter. Growers with young trees need to apply systemic insecticides, while producers with older trees should make foliar applications.

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