Fanleaf degeneration disease caused by grapevine fanleaf virus is thought to be the most serious grapevine virus disease.
Fanleaf virus is transmitted by the nematodes Xiphinema index and X. italiae, which have never been found in Canada.
Infected leaves are often malformed with abnormally gathered primary veins, giving the leaf the appearance of an open fan. Other symptoms may include a yellow mosaic pattern on leaves or bright yellow bands along major veins.
Fan-shaped leaves may or may not be present with mosaic or veinbanding symptoms. The severity of symptoms varies by cultivar.
Affected vines tend to be smaller than healthy vines. Sensitive varieties show progressive decline, low yields (up to 80% losses) and low fruit quality. The productive life of the vineyard is shortened, and winter hardiness is decreased.
There are no natural weed hosts. Long distance spread occurs primarily by movement of propagation material from infected plants.
