Lettuce chlorosis

Pathogen and disease type. Lettuce chlorosis virus (LCV) is a member of the genus Crinivirus within the family Closteroviridae. It is a viral disease characterized by semi-persistent transmission, meaning the virus is acquired and transmitted by its insect vectors without biological replication inside them.

Host range. The primary host is lettuce (Lactuca sativa). However, the virus has a broad host range, infecting various species within the Asteraceae, Solanaceae, and Chenopodiaceae families, which serves as a reservoir for the virus between planting seasons.

Symptoms and signs of infection. The disease manifests as severe interveinal chlorosis (yellowing) on older and middle leaves. Infected leaves often become brittle and thickened. While systemic in nature, the virus does not typically cause severe leaf curling, but the significant reduction in chlorophyll levels drastically reduces plant vigor.

Development conditions and impact. The virus is efficiently transmitted by the greenhouse whitefly (Trialeurodes vaporariorum) and the sweet potato whitefly (Bemisia tabaci). In greenhouse environments, high temperatures and uncontrolled whitefly populations accelerate the spread of the disease, leading to significant yield losses and reduced crop quality.

Control and prevention measures. Management is primarily focused on controlling the insect vectors and reducing the viral load in the vicinity:

• Implementation of strict weed control programs to eliminate alternative hosts.
• Use of insect-proof screening on greenhouse vents.
• Deployment of sticky yellow traps for early detection of whiteflies.
• Application of appropriate insecticides to manage vector populations.
• Sanitation protocols, including the removal of symptomatic plants to reduce the local inoculum source.