Lettuce big-vein disease (BVD) affects all major lettuce-producing areas of the world. The causal agent is Mirafiori lettuce big-vein virus (MLBVV), an ophiovirus transmitted by the soil-borne fungus Olpidium brassicae (Lot et al., 2002). MLBVV has been detected in many different areas of the world but never in Argentina. La Plata has about 700 ha of lettuce with a production of about 13 000 tonnes, and with about 70% of the total production from Buenos Aires Province. BVD has been detected in different areas in the north and west of the La Plata horticultural green belt. Many of the plants with BVD symptoms had leaf distortions of moderate severity, which affected their commercial value.