Ricinus leaf spot

The disease is caused by the fungus Cercospora ricinella, which belongs to the class of Hyphomycetes. It is a specialized pathogen that primarily targets the foliage of its host. The fungus survives unfavorable seasons by persisting as mycelium or conidia on infected plant debris left in the soil or through infested seeds, acting as a reservoir for subsequent infections.

The primary host for this pathogen is the castor bean plant (Ricinus communis). As an economically important oilseed crop, castor bean is highly susceptible to this leaf-spotting disease, which can significantly reduce the photosynthetic capacity of the plant and decrease overall yield quality and quantity.

Symptoms of the infection appear as distinct, circular or angular leaf spots. Initially, these spots are light brown or yellowish in color. As the lesion matures, the central area often turns gray while a dark, defined border forms around the circumference. Under conditions of high humidity, a grayish-olive velvety mold appears on the underside of the leaves, which consists of the fungus's conidiophores and conidia.

The development and spread of Cercospora ricinella are favored by warm, humid weather conditions, with temperatures ranging from +20°C to +28°C being optimal. High rainfall or heavy morning dews provide the necessary moisture for spore germination and infection of the leaf tissue. Spores are easily disseminated by wind, splashing rain, or physical contact within the canopy.

Effective management requires an integrated approach to minimize disease impact. Preventive strategies include deep plowing to bury infected plant residues, ensuring proper spatial arrangement to improve air circulation, and using certified, disease-free seeds. If environmental conditions promote rapid disease progression, the application of appropriate fungicides during the vegetative growth phase is essential to maintain crop health and yield potential.