Fanleaf degeneration/decline disease is one of the most severe viral disease complexes of grapevine worldwide. It is also one of the oldest known viral diseases of Vitis vinifera with descriptions of symptoms being reported in Europe as early as 1841. This disease is now known to affect grapevines in all temperate regions where Vitis vinifera and hybrid rootstocks are grown. Within the United States, fanleaf degeneration/decline is widespread in California, but has also been observed in Washington State, Maryland, Pennsylvania, New York and Missouri.