Leafhoppers as vectors of phytoplasma diseases

Leafhoppers (Cicadellidae) are critical agricultural pests and vectors of economically significant plant pathogens, including phytoplasmas, spiroplasmas and viruses. These pathogens cause devastating diseases resulting in substantial crop losses worldwide. In India, key vector species include Nephotettix virescens, Cicadulina bipunctata, and Orosiusalbicinctus. Despite their importance, vector-pathogen associations remain poorly understood for the majority of species. The subfamily Deltocephalinae, which accounts for 63% of known vector species, plays a central role in pathogen transmission. Tribes such as Macrostelini, Deltocephalini, and Chiasmini harbour numerous vector species capable of spreading mollicutes and plant viruses. Phylogenetic studies reveal the polyphyletic nature of Deltocephalinae, with vectors distributed across multiple lineages, suggesting a substantial number of undiscovered vectors. Feeding preferences, such as xylem or phloem sap ingestion, further influence vector competency and pathogen transmission dynamics. Research has largely focused on agroecosystems and species associated with economically important crops, leaving natural habitats and tropical ecosystems underexplored. The lack of systematic surveys and phylogenetic analyses limits the understanding of the full extent of leafhopper-pathogen interactions. Identifying new vector species, especially in under-studied ecosystems, is critical as many pathogens and vectors may emerge in human-dominated landscapes due to habitat alteration and climate change. Comprehensive studies integrating taxonomy, phylogenetics, and pathogen transmission dynamics are essential for uncovering the evolutionary relationships influencing vector competency. Such insights will facilitate the development of predictive models for identifying potential vector species and designing effective management strategies to mitigate leafhopper-borne diseases in agricultural systems.