Potato mop-top virus causes an economically important disease of potato since serious yield and quality reductions can occur in some cultivars. In potato the virus can cause a wide range of symptoms including dwarfing of shoots (mop-top), pale green V-shaped markings (chevrons) on young leaves, bright yellow blotches, mottling, rings and V-shapes on foliage (aucuba), cracking of tubers and internal necrotic rust-coloured spots, arches and rings within tubers (spraing). The powdery scab fungus (Spongospora subterranea), a soil-borne organism, is the only known vector of potato mop-top virus.