Head smut of maize

Systematic position and nature of the pathogen
Sporisorium reilianum is classified within the kingdom Fungi and the division Basidiomycota. It is a specialized, obligate biotrophic pathogen that predominantly affects maize and sorghum. The fungus is known for its ability to systemically colonize the host plant, resulting in significant morphological changes during the reproductive stage.

Diseases and susceptible crops
The pathogen is the primary cause of head smut of maize. This disease is distinct due to the total replacement of the reproductive floral structures (tassels and ears) with fungal teliospores. While it primarily targets maize, some strains can also impact various wild and cultivated sorghum species.

Biology and lifecycle
The lifecycle of Sporisorium reilianum is soil-borne or seed-borne. Teliospores persist in the soil for several years and germinate when environmental conditions are favourable. The infection occurs at the seedling stage, where the fungus penetrates the mesocotyl and grows systemically towards the apical meristem to colonize the developing reproductive organs.

Conditions for development and harmfulness
Development is highly dependent on soil temperature and moisture. Higher soil temperatures (20–30°C) combined with relatively dry conditions during the germination period significantly increase the infection rate. Economic impact is severe as infected plants often produce no grain at all, directly reducing the total yield per hectare.

Control and management measures

• Use of genetically resistant or tolerant maize hybrids.
• Systemic seed treatment with fungicides that target soil-borne smut pathogens.
• Crop rotation to reduce the concentration of teliospores in the field soil.
• Early planting during periods of optimal soil temperature to minimize the seedling vulnerability window.
• Stringent field sanitation practices to avoid spreading contaminated soil.