Chapter 20

Managing Vineyard Diseases

Viral Pathogens

Grapevine Fanleaf Degeneration

Grapevine fanleaf virus is responsible for fanleaf degeneration, which is one of the most severe virus diseases of grapevines worldwide. Grapevine fanleaf virus causes substantial crop losses, reduces fruit quality and shortens the longevity of grapevines in the vineyard.

Symptoms

Grapevine fanleaf disease can cause symptoms of the leaves, symptoms of the canes and shoots, and symptoms (and losses) of the fruit. Three types of leaf symptoms are common: (1) Fanleaf deformation Leaves are asymmetric with an open petiolar sinus (See Figure 20.17).

Transmission

Fanleaf disease is mostly spread to new sites via diseased planting stocks. Secondary spread is dependent on the presence of nematode vectors— Xiphinema index and X. italiae.

Disease Management

Cultural Practices: The best control for grapevine fanleaf degeneration is to plant only certified virus-free stock.

Chemicals: Soil fumigation (at high rates) works better in shallow than in deep soils, as some nematodes can survive below the depth the fumigant penetrates.

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