Beet necrotic yellow vein virus is the etiological agent of one of the most devastating sugar beet viral diseases: rhizomania. This review describes the molecular biology of the rhizomania disease, the functions of the BNYVV encoded proteins, the consequences of their expression as well as the biology of the BNYVV vector, Polymyxa betae. Root proliferation is an important part of the well-known characteristics of the viral infection that leads to yield and sugar losses. The extensive use of sugar beet cultivars displaying partial resistance or tolerance against virus infection allows containment of sugar yields. However, such extensive uses also permit viruliferous vector to be amplified and therefore the appearance of resistance breaking isolates. We review as well the defence strategies that may be used against rhizomania.