Mulberry latent virus

Mulberry latent virus (MLV) is a plant viral disease characterized by the absence of distinct visual symptoms in infected hosts. This makes it a silent but significant threat in mulberry cultivation. The pathogen persists within the plant tissues, often causing sub-clinical infections that can persist for the entire life of the tree without immediate diagnostic signs.

The primary hosts of this virus are species of the genus Morus (mulberry). While it may not kill the host immediately, the presence of the virus can lead to physiological changes, such as reduced leaf size, minor chlorosis, or decreased overall growth rate, which are often mistakenly attributed to soil quality or environmental stress.

The transmission of the virus is primarily human-mediated, occurring through vegetative propagation. Grafting infected scions onto healthy rootstocks or using infected nursery stock is the most common way for the virus to spread across a plantation. Mechanical transmission via contaminated pruning tools remains a critical factor in nursery and orchard management.

The economic impact is primarily related to the decrease in leaf yield and quality. For producers focused on sericulture, the reduction in leaf quality directly affects the growth and health of silkworms. Furthermore, the systematic nature of the infection means that once a tree is infected, it serves as a permanent reservoir, potentially impacting adjacent healthy trees.

Management of MLV is strictly prophylactic, as there is no cure for systemic viral infections in trees. Controlling the disease relies on the following key practices:

• Sourcing only certified virus-free propagation material for new plantings.
• Implementing rigorous phytosanitary inspection protocols in nurseries.
• Strict sterilization of pruning tools with appropriate disinfectants after every contact with a tree.
• Systematic removal and destruction of infected trees to maintain the health of the entire orchard.