Ascochyta leaf spot of maize

Systematic position and pathogen nature. Ascochyta zeina is a microscopic fungus classified within the division Ascomycota, class Dothideomycetes, order Pleosporales, and genus Ascochyta. It acts as a specialized phytopathogen that targets maize, causing necrotic lesions on its foliage.

Disease and host crops. This pathogen causes Ascochyta leaf spot, primarily affecting maize (Zea mays). The disease is characterized by the appearance of distinct spots on the leaf surface, which can coalesce and lead to significant tissue necrosis, hindering the plant's photosynthetic efficiency.

Biology and life cycle. The life cycle involves the production of pycnidia, which are reproductive structures that release pycniospores. These spores are dispersed via wind and rain splashes to healthy leaf tissue. The fungus survives unfavorable seasons in infected plant debris left in the field, serving as a primary inoculum source for subsequent crops.

Developmental conditions and impact. High humidity, frequent rainfall, and moderate temperatures (approximately 15–22 °C) are conducive to the spread and infection process of Ascochyta zeina. The pathogen's virulence results in reduced green leaf area, causing weakened plants and a significant reduction in grain yield if the infection is widespread.

Control and management measures. To minimize the impact of the disease, farmers should employ the following strategies:

• Implement crop rotation cycles to remove the host plant from infected fields for several years.
• Ensure deep tillage to bury infected crop residues, accelerating their decomposition.
• Choose resistant maize hybrids that show lower susceptibility to leaf pathogens.
• Apply preventive or curative fungicide treatments when weather conditions are favourable for disease development.