Seed Rots and Seedling Blights

Seed rots and seedling blights, caused by Aspergillus fungi, represent a significant threat to agricultural production worldwide. These fungi act as opportunistic pathogens that thrive when crop seeds are compromised by physical injury, poor storage conditions, or environmental stress during the critical germination phase.

Various field crops, with maize being particularly susceptible, suffer from these infections. The pathogen attacks the seed embryo or the delicate tissue of the emerging radicle and plumule. This usually occurs when seeds are planted into cold, wet soil where their metabolic activity is slow, giving the fungus a competitive advantage.

Symptoms of the disease are easily identified by the presence of dense, powdery fungal spores on the seed surface, often displaying distinct shades of yellow, green, or black. Infected seedlings typically show browning, rot, and decay, often leading to pre-emergence damping-off where the plant dies before it even breaks the soil surface.

Development and spread of the pathogen are driven by environmental factors. High moisture content in seeds during storage and high soil moisture combined with suboptimal temperatures at planting create an ideal environment for Aspergillus growth. Spores are easily disseminated by wind and contaminated agricultural machinery.

The economic impact of seed rots is primarily characterized by poor stand establishment and reduced yields. Beyond the physical loss of plants, the accumulation of mycotoxins produced by certain Aspergillus species poses a significant health risk for livestock and human consumption, often leading to the rejection of grain batches.

Effective management and prevention strategies include:

• Utilization of high-quality, certified, and damage-free seeds.
• Comprehensive seed treatment using broad-spectrum fungicides.
• Optimizing planting depth and timing to ensure rapid seed emergence.
• Maintaining proper aeration and drying moisture levels below 14% for stored grain.
• Sanitation practices, such as deep plowing to bury infected crop residues.