Grapevine leafroll-associated virus

Grapevine leafroll-associated virus (GLRaV) is a major viral disease affecting viticulture globally. It is classified within the family Closteroviridae, typically belonging to the genus Ampelovirus. As an obligate parasite, it disrupts the phloem tissue of the grapevine, severely affecting the plant's ability to transport carbohydrates and nutrients.

The virus impacts various grapevine species and cultivars. Symptoms usually appear in late summer and autumn, characterized by the downward rolling of leaf margins and interveinal chlorosis (yellowing or reddening). This physiological disruption leads to delayed ripening, reduced sugar accumulation, and loss of phenolic compounds in berries, significantly impacting wine quality.

The biological cycle of the virus is heavily dependent on insect vectors, primarily mealybugs (Pseudococcidae) and soft scales (Coccidae). These insects acquire the virus by feeding on phloem sap of infected vines and transmit it to healthy plants. Additionally, the virus is spread through vegetative propagation, meaning infected scions or rootstocks will carry the disease into new plantings.

Environmental conditions do not directly dictate the spread of the virus as much as the presence of the insect vectors. Therefore, areas with warmer climates that favor higher populations of mealybugs often face higher infection rates. The virus does not persist in the soil, focusing management strategies on the plant material and vector control.

Effective control strategies focus on prevention, as there is no chemical cure for infected vines:

• Plant only certified virus-free nursery stock.
• Implement rigorous monitoring and control programs for mealybugs and scale insects.
• Rogue out and destroy infected vines immediately upon detection to reduce the primary inoculum source.
• Sanitize pruning equipment to prevent potential mechanical spread.