Diplodia ear rot

Diplodia macrospora (syn. Stenocarpella macrospora) is a destructive fungal pathogen belonging to the Ascomycota division, order Diaporthales. It is a major cause of Diplodia ear rot in corn, capable of significantly damaging both vegetative and reproductive tissues, which leads to major economic losses in maize production worldwide.

The primary symptoms include the development of a dense, white mycelial growth on ears, which eventually leads to the browning and shrinkage of the kernels. Small, black, pimple-like structures called pycnidia appear on the surface of the infected cobs and stalk nodes. Severe infection often causes premature ripening, stalk lodging, and the total degradation of the ear structure.

The life cycle of the pathogen is centered on its ability to survive in crop debris. Pycnidia serve as the primary inoculum, releasing spores during warm and humid weather conditions. Wind and splashing rain disperse these spores onto healthy plants, where they germinate and colonize the tissues. The presence of corn residue is the most critical factor for the persistence of the fungus in the field from one season to the next.

Epidemics are most prevalent in areas with high humidity and moderate to warm temperatures during the late silking and grain-filling stages. Extended periods of rainfall at the end of the season facilitate the movement of spores into the ear, making the crop particularly susceptible. High planting density can also create a microclimate that favors rapid fungal proliferation.

Economic damage includes yield reduction, contamination of grain with mycotoxins, and decreased marketability of the produce. Effective management requires an integrated approach:

• Crop rotation to reduce the load of fungal inoculum in the field.
• Tillage practices that incorporate corn residue to speed up decomposition.
• Selection of resistant or less susceptible maize hybrids.
• Use of effective seed treatments and monitoring of weather conditions during the vulnerable grain-filling period.