AUBURN, Ala. – Citrus greening, a bacterial disease, has been detected in Alabama. During an Alabama Department of Agriculture and Industries (ADAI) annual survey, inspectors identified two trees in a residential landscape in Mobile County with the disease. Now detected in Baldwin County, more surveys are now ongoing by the ADAI to determine the extent of the problem.
Dr. Kassie Conner, an Alabama Extension plant pathologist, said that this disease can cause major damage to the citrus industry.
“Citrus greening can completely destroy the citrus industry,” said Conner. “In Florida, this disease has already affected 75 percent of their citrus. Because of citrus greening, Florida’s economy has lost an estimated $3.63 billion in revenue and over 6,000 jobs.”
The citrus greening bacterium is transmitted through grafting and seed, but is more common through insect transmission. The insect that transmits citrus greening in the United States is the Asian citrus psyllid (ACP).
Conner said that psyllids can be hard to detect.
“ACP is 3 to 4 mm long, which can make them hard to see on the plants,” said Conner. “When you disturb them, they jump out of the way. This also makes it more difficult to see them.”
The thing you are most likely to see first is the effect of the psyllid feeding on the plant. They cause a twisting on the leaf tips, which gives them a rosette appearance. ACP feed on plants in the citrus family, but their preferred host is the Orange jessamine (Murraya paniculata).
Citrus greening infects a plant by getting into the phloem and prevents nutrients from being moved through the vascular system. Several symptoms can arise when a plant has citrus greening. Producers should look for:
- A single yellow shoot on an otherwise healthy-looking plant
- Mottling- a mixing of different hues of green and yellow colors in no specific pattern
- Corky veins- the vein tissues start hardening
- Uneven fruit ripening and also lopsided fruit with dark seeds
- Interveinal yellowing and yellow leaves with green islands
- Dieback can occur in infected trees.
“You will start to see die back, because the branches cannot get nutrients out to the tips,” said Conner. “These trees will eventually die, around two to five years after they are infected.”
Control and Prevention
Once a tree has the disease, there is no way to control it. Conner said that trees with the disease must be removed from the landscape.
“Right now, since they are under federal regulation, infected trees will have to be removed,” said Conner. “Pruning branches that have symptoms will not control the disease. The best way to control the disease is to prevent it.”
To prevent this disease, growers should also use clean budwood that has been certified free of disease. When homeowners purchase new citrus plants, they should only buy trees produced in Alabama or from certified nurseries.
Conner suggests that homeowners scout their citrus plants for psyllids.
“If psyllids are found, then homeowners should look for symptoms of citrus greening on the plants,” said Conner. “Symptoms can appear six months to two years after infection. This makes citrus greening hard to detect.”
In addition, the Alabama Department of Agriculture asks that anyone who suspects that they have an infected tree, contact them to confirm the disease. State inspectors must collect the sample for a positive identification. If you have questions about this disease, contact your local Extension office or also Dr. Kassie Conner at email@example.com.
Featured and First In Text Image: David Hall, USDA Agricultural Research Service, Bugwood.org
Second In Text Image: J.m. Bove, INRA Centre de Recherches de Bordeaux, Bugwood.org
Third In Text Image: H.D. Catling, Bugwood.org