FAN LEAF DEGENERATION or fan leaf virus is a complex of related virus diseases (including yellow mosaic and vein banding).
SPREAD / The virus is spread in two ways, either by man during propagation (in nurseries, in the field) or naturally by nematodes (eg. Xiphinema index) when feeding on affected vine roots before then feeding on unaffected ones.
EFFECTS / Vines develop stunted shoots and malformed ‘fan-like’ leaves, and productivity declines (fewer grapes, smaller bunches).
CONTROL / The nematode vectors can be controlled conventionally by soil fumigation. At replanting growers should use certified virus-free vine stocks. Ideally the land should be left fallow for the soil to be naturally free of both nematode vectors and virus particles–seven years usually, but most growers usually only wait for two or three. Organic growers should dress the land with compost based on cow manure as this contains beneficial nematodes which outcompete or predate (by encircling and then crushing) those nematodes detrimental to the vines.
OTHER NAMES / Court-noué (France).