Crop diseases caused by plant viruses, including the mosaic, streak, spotted wilt and yellow dwarf viruses that reduce yield and quality across cereals, vegetables and tropical staples, most spread by an insect or other vector rather than direct contact. Belongs here: any crop disease whose recognized causal agent is a virus. Does not belong here: the insect vector that spreads a viral disease, which is its own entity grouped under Insect and Mite Pests of Crops when it is minted as a pest in its own right.