Ladder leaf spot of sorghum

Ladder leaf spot is a fungal disease affecting sorghum crops, caused by the pathogen Passalora fusimaculans (formerly Cercospora fusimaculans). This disease is recognized as a significant foliar pathogen that can affect crop health in warm and humid climates.

The primary host for this fungus is sorghum. By attacking the foliage, the pathogen reduces the plant's capacity for photosynthesis, which is critical during the vegetative growth stages and grain filling, potentially leading to lower yields and reduced grain quality.

Symptoms are distinct and characterized by elongated, rectangular spots that occur between the leaf veins. These lesions often show a ladder-like appearance, giving the disease its common name. As the infection progresses, the lesions may coalesce, leading to extensive necrosis of the leaf tissue.

The fungus thrives in conditions of high humidity and moderate to warm temperatures, which are ideal for the production and dispersal of conidia. These spores are spread through wind and rain splash, allowing the pathogen to move rapidly through a field, particularly when the canopy is dense and air circulation is poor.

Effective management strategies rely on integrated pest management practices:

• Implementing crop rotation to reduce inoculum pressure in the soil.
• Removing or deeply incorporating infested plant debris after harvest.
• Utilizing disease-resistant sorghum varieties.
• Applying appropriate fungicides if environmental conditions favor severe disease development.