[8] Citrus greening is distinguished by the common symptoms of yellowing of the veins and adjacent tissues (hence the "yellow dragon" name given by observing Chaozhou farmers as early as the 1870s[1]); followed by splotchy mottling of the entire leaf, premature defoliation, dieback of twigs, decay of feeder rootlets and lateral roots, and decline in vigor, ultimately followed by the death of the entire plant.
[9] Affected trees have stunted growth, bear multiple off-season flowers (most of which fall off), and produce small, irregularly shaped fruit with a thick, pale peel that remains green at the bottom and tastes very bitter.
[10] Citrus greening was originally thought to be a viral disease, but is caused by a bacterium, carried by insect vectors.
L. asiaticus by the Asian citrus psyllid Diaphorina citri,[14] and some cultivars show greater efficiency in transmitting the disease to the vector than others.
The disease has affected crops in China, India, Sri Lanka, Malaysia, Indonesia, Myanmar, the Philippines, Pakistan, Thailand, the Ryukyu Islands, Nepal, Saudi Arabia, and Afghanistan.
[25] The distribution of the African citrus psyllid includes Africa, Madeira, Saudi Arabia, Portugal, and Yemen.
This strain is reported to occur in Africa, (Burundi, Cameroon, Central African Republic, Comoros, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Reunion, Rwanda, South Africa, St. Helena (unconfirmed), Swaziland, Tanzania, Zimbabwe), Saudi Arabia, and Yemen.
Cultural methods include antibacterial management, sanitation, removal of infected plants, frequent scouting, and most importantly, crisis declaration.
Ongoing challenges associated with mitigating disease at the field-scale include seasonality of the phytopathogen (Liberibacter spp.)
and associated disease symptoms, limitations for therapeutics to contact the phytopathogen in planta, adverse impacts of broad-spectrum treatments on plant-beneficial microbiota, and potential implications on public and ecosystem health.
[33] Field tests by Southern Gardens Citrus of oranges with the spinach genes in Florida are ongoing.
[37] Certain antibiotics, specifically streptomycin and oxytetracycline, may be effective and have been used in the United States, but are banned in Brazil and the European Union.
[42] Two types of antisense oligonucleotide (FANA and Morpholinos) can be delivered efficiently into citrus trees,[43] suppressing their RNA targets.
[49] The citrus trees were not free of the disease bacteria, yet a healthy soil environment allowed them to produce fruit and remain profitable.