Microdochium sorghi

Taxonomic position and pathogen type: Microdochium sorghi (formerly known as Gloeocercospora sorghi) is a fungal pathogen classified within the Ascomycota phylum. It is a specialized plant pathogen that primarily attacks cereals, causing necrotic lesions on foliage and significantly impacting the health and vigor of the host plant in various agricultural settings.

Diseases and host plants: This pathogen is the causal agent of gloeocercospora leaf spot (also known as zonate leaf spot). It specifically targets various sorghum varieties, including grain sorghum, forage sorghum, and sudangrass. The infection is characterized by distinct, circular or elongated lesions that display red, purple, or tan coloration, eventually causing tissue death across the leaf surface.

Biology and life cycle: The fungus overwinters as sclerotia or mycelium in infested crop debris left in the soil, and it can also be seed-borne. When conditions become favorable in the growing season, the pathogen produces conidia. These spores are disseminated primarily through wind-blown rain and splashing water, allowing the fungus to infect fresh leaf tissue through stomata or mechanical injuries.

Development conditions and impact: Microdochium sorghi thrives in environments characterized by high humidity and warm temperatures, typically between 20°C and 28°C. The damage caused by this pathogen is significant; it reduces the leaf area available for photosynthesis, which impairs the plant's ability to produce energy, ultimately leading to reduced grain filling, lower biomass yield, and degraded silage quality.

Protection and control measures: Managing Microdochium sorghi requires an integrated pest management (IPM) strategy focused on minimizing infection pressure:

• Planting resistant or tolerant sorghum hybrids.
• Implementing deep plowing or tillage to bury infected plant residues.
• Practicing long-term crop rotation to eliminate the host environment for the fungus.
• Treating seeds with appropriate fungicides and applying foliar sprays during high-risk weather conditions to prevent early-season outbreaks.