Common bunt

Common bunt, also known as stinking smut, is caused by the fungus Tilletia caries. It is a systemic plant disease that typically infects wheat seedlings. The fungus colonizes the plant tissues throughout the vegetative growth period, eventually invading the developing ovary of the wheat head and replacing the interior of the grain with a mass of teliospores.

The disease primarily affects common wheat, durum wheat, and occasionally rye. The pathogen is soil-borne and seed-borne. Spores persist in the soil for several years and can also contaminate healthy grain during the harvesting process, remaining on the surface of the seeds until they are planted in the following season.

Symptoms are often difficult to detect until the plant reaches the heading stage. Affected plants may show stunted growth, and the infected heads often remain green longer than healthy ones. Instead of filling with starch, the kernels become bunted, filled with a black powdery mass of spores that emit a distinctive fishy or rotten-fish odor due to the presence of trimethylamine.

The infection process is highly dependent on environmental factors. The fungus thrives at soil temperatures between +5°C and +12°C. Cool and moist soil conditions at planting time are optimal for spore germination and infection of the coleoptiles. Once the plant has progressed beyond the seedling stage, it becomes resistant to initial infection.

The impact of common bunt is significant, leading to severe yield losses and grain contamination that makes the harvest unsuitable for milling or livestock feed. Effective control measures include the use of disease-resistant varieties, professional seed dressing with systemic fungicides, and appropriate crop rotation. Additionally, planting wheat when soil temperatures are outside the optimal range for the fungus helps to reduce infection incidence.