Citrus Huanglongbing (HLB) or citrus greening disease has been in Florida since at least 2005 and has spread to all of the citrus producing regions. The Asian citrus psyllid (Diaphorina citri) is the insect that transmits the suspected causal bacterium which is tentatively named Candidatus Liberibacter asiaticus. Symptoms of the disease are first the yellow shoot (huanglongbing) and the development of the blotchy mottle symptom in the leaves. Mineral deficiency symptoms are often found on infected trees and may mimic normal deficiency symptoms. Fruit on infected trees may be small and lopsided and may abscise prematurely and therefore productivity is reduced. Tree decline eventually occurs. The suspected causal bacterium has not been obtained in pure culture and a polymerase chain reaction (PCR) test along with symptoms, is the only way to verify infected trees. All citrus cultivars appear susceptible. Current management strategies are chemical and biological control to reduced psyllid populations, inspections for infected trees and removal of infected trees to reduce the available pathogen inoculum. Current research on psyllid control, psyllid transmission, symptomology, detection, culturing the causal agent, development of new detection methods, alternative hosts of the psyllid and the causal agent, physiology of the disease, resistant or tolerant cultivar development and more is discussed. HLB is a major problem for citrus production and often limits commercial production.
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