Blueberry scorch

Blueberry scorch is a viral disease caused by the Blueberry scorch virus (BlScV), a member of the Carlavirus genus. It represents a significant threat to the production of highbush blueberries and cranberries, as it can cause substantial yield losses and weaken entire plantations over several growing seasons.

The virus affects both blueberry and cranberry crops. Once a plant is infected, the virus becomes systemic, spreading through the vascular tissues. This makes infected plants a continuous source of infection for neighboring healthy bushes, eventually leading to reduced fruit production and compromised plant vigor.

Symptoms are most distinct during the flowering stage. Affected bushes display a sudden blighting of blossoms, which turn brown or black and wither without falling off. This is often accompanied by yellowing of the foliage and marginal leaf necrosis. The severity of these symptoms can vary depending on the plant cultivar and environmental conditions.

The virus is primarily transmitted by various species of aphids. These vectors acquire the virus while feeding on infected plant sap and transmit it to healthy bushes during subsequent feedings. The spread is facilitated by warm conditions that promote aphid activity and high planting densities that allow for easy movement of the vectors between bushes.

Management of blueberry scorch is strictly preventative, as there is no chemical cure for the virus. Growers should prioritize the purchase of virus-indexed, certified nursery stock. Effective control involves constant scouting for symptomatic plants, immediate rogueing and destruction of infected bushes, and rigorous integrated pest management to keep aphid populations below the economic threshold.