Corky bark

The virus relies on vegetative propagation of the host, Vitis vinifera, to spread across different regions. It can persist in the wood and root system indefinitely.

Natural transmission occurs through insect vectors, specifically mealybugs (e.g., Planococcus ficus), which acquire the virus while feeding on infected phloem sap.

The pathogen is known for its ability to complex with other viruses, creating a synergistic effect that leads to severe decline in grapevine vigor.

Once a vine is infected, the virus spreads systemically, making it impossible to cure the plant using traditional chemical treatments.

Symptoms typically become apparent on the current season's shoots during late summer. The bark becomes thick, rough, and develops a corky texture.

Shoots often exhibit stunted growth and shortened internodes, giving the vine a weak and distorted overall appearance.

Peeling the bark reveals pitting or grooving on the woody cylinder, which is a classic diagnostic symptom of severe corky bark infection.

Leaves may show discoloration, appearing reddened or chlorotic, and often display downward curling along the margins.

Grape clusters are usually small and poorly filled, with berries showing reduced sugar content and irregular ripening patterns.

The spread of the virus is heavily linked to the use of infected nursery stock. Planting materials sourced from non-certified mother blocks are the primary route of infestation.

Warm and temperate climates provide ideal conditions for the activity of mealybugs, which are essential for the transmission of the virus within a vineyard.

Poor sanitation practices in the nursery, including the lack of testing for viruses, facilitate the silent spread of GVB to new plantations.

Vineyards with high planting density are more susceptible to rapid outbreaks because insect vectors can easily move between adjacent vines.

Environmental stress can exacerbate symptom expression, making it easier to identify infected vines during hot and dry summer months.

Corky bark causes progressive yield decline, leading to significant economic losses for grape growers over several seasons.

The structural integrity of the vine is compromised as the wood becomes brittle and prone to breakage under the weight of the crop.

Fruit quality is severely impacted, making the harvest unsuitable for high-quality wine production due to poor acidity and sugar balance.

Infected vines have a reduced lifespan and often require complete removal, increasing the overall cost of vineyard replacement.

The presence of the virus undermines the long-term sustainability of the vineyard, as it serves as a permanent reservoir of infection for healthy plants.

The most effective strategy is the use of certified virus-free planting material. Growers must ensure that nurseries follow strict viral indexing protocols.

Implementing a rigorous pest control program targeting mealybugs is critical to stopping the vector-mediated spread of the virus.

Strict hygiene measures, including the disinfection of pruning tools with alcohol, are necessary to prevent mechanical transmission during vineyard operations.

Immediate roguing (removal and destruction) of symptomatic vines is essential to lower the inoculum pressure within the vineyard block.

• Use only certified propagation material.
• Monitor and control mealybug populations.
• Sterilize pruning equipment regularly.
• Remove and burn infected vines immediately.
• Maintain buffer zones from old, unknown-status vineyards.