Green mottle

Green mottle is a significant viral disease that primarily affects pome fruit trees, with the domestic apple tree (Malus domestica) being one of its most common hosts. The condition is triggered by the Apple mosaic virus (ApMV) or similar viral strains that colonize the plant's vascular system, disrupting normal physiological functions.

The pathogen is systemic, meaning it spreads throughout the entire plant tissue, including roots, stems, and leaves. Transmission primarily occurs through vegetative propagation methods, such as grafting with infected scions or rootstocks. Additionally, mechanical transmission during pruning operations, where contaminated tools are used, is a common pathway for viral spread.

Symptoms of green mottle are visually distinct during the active growing season. Affected foliage displays irregular chlorotic patterns, often manifesting as light green or yellow spots and blotches, hence the name. In severe cases, these symptoms can lead to leaf malformation, reduced leaf area, and stunted shoot growth, which drastically lowers the plant's photosynthetic efficiency.

Environmental conditions that favor active sap flow facilitate the movement of the virus within the tree. The virus remains dormant in the tissues during winter but becomes highly active as the temperatures rise and the tree initiates spring growth. Stress factors, such as drought or poor soil management, can exacerbate the visual symptoms of the infection.

The economic impact of green mottle is severe, as it causes a decline in fruit quantity and quality, and weakens the overall vigor of the tree. Since there is no cure for systemic viral infections in orchard crops, the primary management strategy focuses on strict prevention and sanitary protocols to maintain orchard health and productivity.

• Sourcing certified virus-free planting material from reputable nurseries.
• Strict sterilization of pruning equipment between different trees.
• Regular monitoring and immediate culling of infected trees.
• Minimizing mechanical wounds on the tree trunk and branches during cultivation.