Cercospora leaf spot of sorghum

Cercospora sorghi is a significant fungal plant pathogen belonging to the kingdom Fungi and the genus Cercospora. It is recognized as the primary agent responsible for Cercospora leaf spot, a disease that frequently affects sorghum crops worldwide, leading to reduced photosynthetic capacity and crop yield losses.

The disease primarily manifests as leaf lesions which are typically oblong, rectangular, or irregular in shape, ranging from tan to red or purple, depending on the host genotype. As the infection progresses, these spots coalesce, causing large areas of leaf tissue to necrotize. This damage significantly interferes with the plant's metabolic processes during critical grain-filling stages.

The biology and lifecycle of the pathogen are closely linked to high humidity and moderate temperatures. The fungus produces conidia, which serve as the primary inoculum and are disseminated via wind and splashing rain. The pathogen overwinters as mycelium or stromata within infected plant debris, ensuring its survival between growing seasons in the soil or on dormant crop residues.

Environmental conditions characterized by frequent rainfall, high relative humidity (above 80%), and temperatures ranging from 22°C to 30°C are highly conducive to disease development. Dense canopy structures, which trap moisture and limit airflow, create an ideal microclimate for the fungus to multiply rapidly throughout the vegetative growth period.

The economic impact of this pathogen is reflected in reduced grain weight and overall plant vigor. Effective control and disease management require an integrated approach involving several key strategies:

• Selecting and planting sorghum hybrids with confirmed genetic resistance.
• Implementing crop rotation cycles to disrupt the pathogen's survival in the soil.
• Removing or burying crop residues to reduce the initial inoculum level.
• Ensuring proper plant spacing to improve air circulation within the field.
• Applying registered foliar fungicides if disease thresholds are exceeded during the growing season.