Plant virus and sub-viral agents cause considerable losses in crop production as they are so widely spread.  They are transmitted by means of vegetative propagation of seedlings and also through insect vectors.  They infect field crops, vegetables, cereals, oil seeds, fruit crops and ornamentals.  The virus may enter into plants through seed / planting material or by vectors.  Once the virus is in the field, it multiplies and spreads following definite patterns depending upon the nature of the vector and agro-meteorological conditions. Detection of virus and sub-viral agents at initial stages of infection is critical to reduce economic losses.  For nearly two decades, ELISA and its variants played a major role in large scale virus testing and also in the production of virus-free planting materials.  In recent years nucleic acid - based molecular detection methods such as the amplification of nucleic acids (PCR and its variants), microarrays, rDNA technology, DNA barcoding, DNA biosensors and other improved techniques are playing pivotal role in specific virus testing, identification of new viruses, virus strain differentiation, identification of virus relationships and other biological aspects, as these techniques are specific, sensitive and reproducible.  Nevertheless, integrated management measures have evident benefits and should be fostered and promoted for managing virus and sub-viral diseases for enhancing crop productivity. This book provides the latest valuable overview of the plant virus and virus-like diseases in tropical countries on aspects like introduction about plant viruses, their classification; transmission and diagnostic techniques; the well written chapters are thoroughly up-to-date and amply and clearly illustrated with numerous photographs.  It is a good source of information on plant virus and sub-viral pathogens to all plant virologists, students, faculty, research and quarantine organizations.