Iris yellow spot orthotospovirus, an emerging pathogen affecting Allium spp and ornamental crops, has been identified in over 92 countries and states/provinces worldwide. It is classified within the family Tospoviridae and the genus Orthotospovirus. As a member of the genus Orthotospovirus, it is transmitted by thrips (specifically Thrips tabaci and Frankliniella fusca) in a circulative and propagative manner. This pathogen leads to significant yield losses in ornamental plants and cultivated alliaceous crops such as onion, garlic, and leeks. This chapter aims to provide an in-depth exploration of the virus’s geographical distribution, biology, epidemiology, diagnosis, and strategies for pathogen control.