Yellow spot of sugarcane

Systematic position and pathogen type: The fungus Mycovellosiella koepkei (formerly Cercospora koepkei) is an Ascomycota pathogen responsible for the disease known as yellow spot of sugarcane. It is a highly specialized plant pathogen that limits its host range to the Saccharum genus, causing significant foliar damage under favorable climatic conditions.

Disease and host plants: The primary host is sugarcane. The disease is characterized by the appearance of small, pale-yellow spots on the leaves. As the infection progresses, these spots expand, coalesce, and often turn reddish-brown. In humid conditions, a gray-olive mold consisting of conidiophores and conidia develops on the underside of the leaf, which serves as a diagnostic sign for the presence of the pathogen.

Biology and life cycle: The lifecycle of Mycovellosiella koepkei involves the production of conidia that are disseminated by wind, rain splashes, and agricultural machinery. The fungus persists between seasons in infested plant debris and soil, which serves as the primary inoculum source. Under favorable conditions, the germination of spores leads to rapid colonization of leaf tissue through stomata or direct penetration.

Development conditions and impact: Disease development is highly dependent on environmental factors, particularly high humidity (above 85%) and moderate temperatures (22–28°C). The economic damage is significant as the disease causes extensive leaf necrosis, reducing the photosynthetic capacity of the plant. This loss of canopy efficiency leads to a reduced sugar content in the stalks, significantly impacting juice purity and overall harvest yield.

Protection and control measures: Effective management of yellow spot involves an integrated approach to maintain crop health:

• Selection and planting of resistant sugarcane cultivars as the primary preventive measure.
• Sanitation practices, including the removal and destruction of crop residues to reduce primary inoculum levels.
• Maintaining optimal planting distances to enhance air circulation and reduce leaf wetness duration.
• Application of systemic or contact fungicides when the threshold of infection is reached, following regional agricultural guidelines.