Citrus Huanglongbing (HLB)

Biochemical Mechanisms of HLB in Citrus

Citrus Huanglongbing (HLB), also known as greening, is caused by a phloem-limited bacterium Candidatus Liberibacter asiaticus that has a true cell wall, but has not been cultured. A citrus insect Asian citrus psyllid, Diaphorina citri, as a vector, transmits the bacterium between infected trees to healthy ones. Citrus greening is an exotic disease to Florida, and the disease has rapidly spread in Florida’s citrus growing regions since it has first been detected in 2005. There is very limited resistance found among different commercial citrus varieties grown in Florida. Control of citrus greening is difficult if inoculum sources are widespread and the psyllid vector is well established. Psyllid control is one major emphasis on battling this disease.

The destructiveness, fast spread and difficult control of citrus greening have all become evident as the most significant threat to the current Florida citrus industry. Therefore, urgent and extensive research on citrus greening is needed to find ways to effectively control this disease and protect the citrus industry. The current research projects in this area focuses on: (1) searching for more and effective biochemical markers for disease detection, especially in early stages; (2) understanding molecular and biochemical mechanisms of pathogenesis and virulence of the pathogen; and (3) developing new and effective disease control methods.