Mulberry powdery mildew

The causative agent of this disease is Phyllactinia moricola, a fungus belonging to the Erysiphaceae family. As an obligate parasite, it relies entirely on the tissues of its host plant to obtain nutrients, typically invading the leaf epidermis via specialized structures known as haustoria.

The primary host for this pathogen is the mulberry tree (genus Morus). It is particularly significant in regions where mulberry leaves are essential for silkworm rearing, as the quality and quantity of foliage are directly affected by the fungal infection, leading to substantial economic losses in sericulture.

Symptoms of the infection typically appear on the abaxial (lower) surface of the leaves, manifesting as a thin, white, felt-like mycelial growth. As the fungus matures, small, dark, globose fruiting bodies called cleistothecia emerge, turning the patches into greyish-black spots, which distinguishes this species from other powdery mildew fungi.

The development and spread of Phyllactinia moricola are heavily influenced by environmental factors, particularly high humidity and moderate temperatures. The fungus produces large quantities of conidia, which are efficiently dispersed by wind currents, allowing the pathogen to spread rapidly across orchards and nurseries during the growing season.

Effective management requires an integrated approach to minimize disease impact. Preventive measures include ensuring good orchard hygiene by removing and disposing of infected plant debris, thinning tree canopies to improve airflow, and applying appropriate fungicidal sprays when local climatic conditions favor rapid pathogen spread.