Fanleaf degeneration/decline disease of grapevines

Introduction 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. Causal Agents Fanleaf degeneration/decline disease is caused by several different virus species (Table 1). Viruses causing fanleaf degeneration/decline are nepoviruses (acronym for ne = nematode-borne; po = polyhedral particle) (Figure 1). Grapevine fanleaf virus (GFLV) is the most wellcharacterized nepovirus, and is by far the most widespread and important cause of the disease worldwide. In the United States, GFLV, Arabis mosaic virus (ArMV), Tomato ringspot virus (ToRSV), Tobacco ringspot virus (TRSV), Peach rosette mosaic virus (PRMV), and Blueberry leaf mottle virus (BLMoV) have been reported in fanleaf-affected vines. However, only ToRSV, TRSV, and BLMoV have been found in New York State vineyards.