Plant virus infections are estimated to cost billions of dollars in economic losses. Despite intensive efforts to manage and prevent plant viruses and their potential vectors in crop production processes, the threat posed by newly emerging or re-emerging viruses is becoming more common and poses potential threats even in previously uninfected areas. In this new volume, the editors review the progress made and the challenges ahead to address the hidden world of plant viruses, their impact on agriculture and food security, and the need for new detection systems and management strategies.