Covered kernel smut

The fungus functions as an obligate parasite, infecting the host plant during the germination stage. The infection process begins when teliospores germinate simultaneously with the sorghum seed in the soil.

Once inside the host, the pathogen grows systemically throughout the plant's tissues, typically remaining dormant and invisible until the reproductive phase is reached.

The fungal mycelium colonizes the developing floral structures, eventually replacing the internal contents of the ovaries with mass quantities of dark spores.

The pathogen is primarily seed-borne, but soil-borne inoculum can also contribute to the initial infection in fields with a history of the disease.

The primary damage caused by this pathogen is the complete destruction of grain in affected heads. The ovaries are replaced by smut sori (galls) filled with fungal spores.

This results in significant yield reduction, as the grain on infested plants is entirely non-viable and unfit for processing or livestock feed consumption.

In addition to direct yield loss, the presence of smut spores reduces the overall quality and marketability of the harvested crop due to contamination.

The disease can also weaken the overall vigor of the host plant, potentially leading to stunting or increased susceptibility to other environmental stressors.

Economic losses are compounded by the necessity of purchasing specialized fungicides and performing decontamination of harvesting equipment to prevent further spread.

Symptoms become apparent during the flowering and heading stage. Instead of normal grains, the sorghum head develops characteristic greyish or brown smut sori.

These sori remain relatively intact during development, keeping the mass of black teliospores enclosed within a thin membrane, which gives the disease its "covered" name.

As the plant matures, the protective membrane eventually ruptures, releasing a cloud of black, powdery spores that are dispersed by wind, rain, and machinery to nearby plants.

Infected plants often exhibit stunted growth and abnormal tillering compared to healthy plants, making them easier to spot during the growing season.

The dark appearance of the head is the most reliable diagnostic feature for field scouting during the grain-filling period.

Effective management begins with the use of certified, disease-free seed. Seed treatment with systemic fungicides is the most crucial control measure to eliminate seed-borne spores.

Crop rotation helps to reduce the inoculum level in the soil, preventing the build-up of the pathogen in fields repeatedly planted with sorghum.

Planting sorghum when soil conditions are favorable for rapid germination and emergence helps the crop escape the window of peak susceptibility to infection.

Selecting and planting resistant sorghum hybrids is a sustainable strategy that significantly lowers the reliance on chemical control methods over time.

• Systemic seed treatment fungicides.
• Use of resistant hybrid cultivars.
• Proper crop rotation cycles.
• Timely harvesting to reduce spore dispersal.