Common bunt of wheat

Taxonomic position and pathogen nature. Tilletia caries is a basidiomycetous fungus within the Ustilaginomycetes class. It is an obligate parasite, recognized as one of the most significant seed-borne and soil-borne pathogens affecting wheat crops globally.

Disease and host plants. The fungus causes common bunt (also known as stinking smut). It primarily targets wheat (both winter and spring varieties). The disease is often unnoticed until maturity, when infected wheat heads appear slightly thinner, and the kernels are replaced by dark, powdery teliospore masses that emit a distinct fishy odor.

Biology and life cycle. The infection cycle is initiated when teliospores germinate simultaneously with the wheat seed in the soil. The fungus produces a mycelium that infects the seedling before it emerges from the soil surface. Once inside the plant, the pathogen grows systemically alongside the host's meristematic tissue until the reproductive stage, where it transforms the grain into sori.

Development conditions and impact. The pathogen thrives in cool, moist soil conditions, typically ranging from 5°C to 15°C. The economic impact is severe: it causes significant yield losses and reduces grain quality. Contaminated grain is often rejected by millers due to the foul odor and the presence of fungal spores, which can also trigger dust explosions in processing facilities.

Control and management measures. Management focuses on prevention as there is no cure once the plant is systemically infected. Key strategies include:

• Thorough seed treatment with broad-spectrum systemic fungicides.
• Use of certified, disease-free, and resistant wheat cultivars.
• Strategic crop rotation to reduce spore load in the soil.
• Adherence to recommended planting depths to allow rapid seedling emergence, bypassing the most susceptible early development phase.