The Encyclopedia of Plant Viruses and Viroids provides an up-to-date information on the viruses and viroids infecting all types of cultivated and weed plants at global level; and is unique among plant virology texts as it is organized alphabetically by the genus name of the host plant infected. It allows the reader to readily determine all of the different viruses currently reported naturally infecting the plant genus and species. Information is provided for each virus and viroids on common synonyms, current taxonomic status, geographical distribution, symptoms induced, other known hosts, means of transmission and properties of both the virus particles and the genome. Where ever the same virus is known to infect multiple hosts, host-specific information, biological properties and genome characters are presented under each host affected. The index can be utilized to identify other crops infected by the same virus, showing which other crops might be at risk of infection in the event of introduction of a virus that has not previously reported in an area, or which might serve as potential virus reservoirs for infection of more sensitive or economically important crops than the host in which it is initially identified. The taxonomy and nomenclature of the viruses and viroids are followed based on the current guidelines of the 10th ICTV Report, covering up to 2018 and also about many new viruses and viroids that have been reported but not yet recognized as species by ICTV, have been included in this Encyclopedia. The uniqueness of this Encyclopedia is that all the known viruses and viroids affecting more than 1010 plant species at global level are described and the plant species are arranged in alphabetical order of the scientific name of the plant along the relevant information on 1518 viruses and viroids and is the ready-reckoner of the global plant species and their viruses and viroids for students, scientists, teachers of Plant Pathology& Virology; and also for the crop protection professionals, agricultural policymakers, seed companies and quarantine agencies.