Huanglongbing: What is Known So Far About the Greatest Threat to the Worlds Citrus Industry?

Huanglongbing (or HLB) is the most devastating citrus disease that is widespread throughout the world, causing enormous economic damage to the citrus industry and making oranges and the juice produced with them of lower quality for consumption. The presumptive causal agent of the disease is the bacteria Candidatus Liberibacter spp. that has not yet been cultivated in vitro, with three species: Ca. L. asiaticus, Ca. L. americanus and Ca. L. africanus. Currently, there is no cure for HLB disease. The disease has been managed by the use of healthy nursery trees; monitoring and controlling the psyllid vector; and scouting and eradication of symptomatic trees. One of the alternatives to reduce the problem, currently in use in Florida, USA, has been the prolonged use of antibiotics; however, the long-term practice may be harmful to human health and to the environment. In this sense, the main objective of the present review is to discuss strategies applied to gain deeper understanding concerning chemical and biochemical aspects of HLB disease and review different methodologies to be potentially applied to control the spreading of the disease in the fields and to avoid the increase of the incidence in the orchards.