Insects as vectors and emerging trends in plant disease transmission

Abstract

Insect vectors play a central role in the global spread of plant diseases across agronomic and horticultural crops. Hemipteran insects (e.g. aphids, whiteflies, leafhoppers, plant hoppers, psyllids, mealy bugs) dominate as vectors, transmitting most plant viruses, bacteria (phytopathogens) and phytoplasmas in diverse cropping systems. Insect transmission can be non-persistent (stylet-borne), semi-persistent (foregut-borne) or persistent circulative/propagative, depending on virus localization and retention in the vector. Viral diseases include geminiviruses (whitefly-begomoviruses), potyviruses (aphid-transmitted), luteoviruses, tospoviruses (thrips-transmitted) and others. Bacterial and phytoplasmal diseases (e.g. citrus greening by Liberibacter, yellows by phytoplasmas) are spread by xylem- and phloem-feeding hemipterans. Fungal pathogens (e.g. Dutch elm disease Ophiostoma by bark beetles) and nematodes (e.g. pinewood nematode by sawyer beetles) are also vectored by insects. Emerging trends include advances in genomics of vector-pathogen interactions, novel control technologies (RNAi, CRISPR, endosymbiont manipulation) and the impact of climate change on vector biology. Integrated disease management requires combining host resistance, cultural practices, biological control of vectors and precise monitoring and forecasting. Global case examples (e.g. begomovirus epidemics, citrus huanglongbing, Xylella outbreaks) and Indian scenarios (e.g. rice tungro, cotton leaf curl virus) illustrate the complexity of vector-mediated epidemics. This review synthesizes current knowledge on insect vectors, transmission mechanisms and management of vector-borne plant diseases, with an emphasis on recent research advances and global/Indian case studies.