Grapevine fanleaf virus

Grapevine fanleaf virus (GFLV) is a devastating plant disease commonly associated with little leaf syndrome and shoot malformation. It is a nepovirus transmitted primarily by soil-dwelling nematodes of the genus Xiphinema. The virus interferes with the physiological processes of the grapevine, leading to structural instability and poor productivity.

The host range is essentially limited to the genus Vitis. Commercial vineyards are particularly vulnerable, especially when established on sites previously infested with vector nematodes. Once a vine is infected, the virus becomes systemic, moving through the phloem to all parts of the plant, ensuring that the entire vine remains a source of inoculum for the rest of its life.

Symptoms are highly characteristic: leaves become stunted, crinkled, and show asymmetrical growth with serrated margins. The shoots often display short internodes and double nodes, resulting in a distorted or fan-like appearance. Flowers frequently fail to set properly, causing significant "coulure" or berry shatter, which drastically reduces the yield of high-quality grapes.

Environmental conditions that favor the survival and mobility of nematodes in the soil significantly increase the risk of spread. These viruses thrive in well-structured, moist soils where vector populations can migrate. Furthermore, the disease is frequently disseminated over long distances through the international trade of infected cuttings and rootstocks, which may appear asymptomatic in early stages.

Control measures are strictly preventive because no chemical treatment can cure an infected vine. Successful management involves

• Sourcing certified virus-free planting material.
• Fallow periods and soil fumigation to eliminate vector nematodes.
• Immediate roguing and destruction of symptomatic plants.
• Sanitization of pruning shears to avoid mechanical transmission.