Marssonina leaf spot of mulberry

Marssonina necans is a fungal pathogen primarily responsible for leaf spot disease in mulberry trees (Morus spp.). This disease belongs to the anthracnose group and can lead to severe defoliation if left untreated, causing significant economic damage in areas where mulberry leaves are harvested for sericulture.

Symptoms typically appear as small, brownish or black circular spots on the leaf blades. As the infection progresses, these spots expand, often merging into larger necrotic areas. The affected leaf tissue may become brittle and crack, resulting in a shot-hole appearance, followed by chlorosis and premature abscission of the leaves.

The development of this disease is highly dependent on environmental conditions, particularly high humidity and moderate temperatures during the growing season. The fungus produces conidia, which are easily disseminated by wind and water splashes from infected foliage. The pathogen survives the winter in fallen leaves and on infected twigs, serving as a primary source of inoculum for the next year.

The economic impact of Marssonina necans is substantial, as it directly affects the quantity and quality of mulberry foliage. Since the leaf is the sole food source for silkworms, premature leaf loss negatively impacts silk production. Furthermore, infected trees show reduced vigor, stunted growth, and decreased tolerance to environmental stresses like winter frost.

Effective disease management relies on integrated control strategies, starting with strict sanitation practices such as the removal and destruction of fallen leaves during autumn to eliminate overwintering spores. In addition, chemical control using copper-based fungicides or appropriate systemic sprays applied during the early stages of the growing season can help reduce disease incidence and protect the canopy.