Understanding psyllid transmission of Candidatus Liberibacter as a basis for managing huanglongbing

Abstract

Citrus huanglongbing (HLB) represents a major threat to citriculture due to its rapid spread, difficulty of control, severe yield losses, and substantial increases in production costs in HLB-affected orchards. Successful management depends on detailed knowledge of the epidemiology of this disease, which is associated with phloem-limited bacteria of the genus Candidatus Liberibacter that are transmitted by phloem sap–feeding insects known as psyllids (Hemiptera: Psylloidea). Candidatus L. asiaticus (CLas) and the Asian citrus psyllid Diaphorina citri Kuwayama are the major etiological agent and vector, respectively, in the Americas and Asia. This review provides up-to-date information on the relationships of psyllid vectors with Ca. Liberibacter spp. associated with HLB, with emphasis on D. citri and CLas. Knowledge of the transmission mechanisms of these bacteria, as well as aspects of the biology, ecology, and behavior of the vector in relation to the environment, is essential to gain understanding of the HLB epidemics. Such knowledge provides a basis for developing innovative control methods and establishing sustainable management strategies for HLB.