Common bunt

Common bunt, caused by the fungus Tilletia caries, is a devastating disease affecting cereal crops worldwide, particularly wheat. It is a systemic disease that colonizes the plant from the seedling stage, eventually replacing the developing grain kernels with masses of dark, powdery fungal spores within the glumes.

The infection process starts primarily from spores adhering to the seed surface or resting in the soil. As the seed germinates, the fungus penetrates the coleoptile. Once inside the plant, the pathogen grows systemically alongside the growing point, remaining mostly dormant until the plant reaches the heading stage, where it migrates into the ovaries to produce spore balls.

Symptoms become apparent at the ripening stage. Infected heads often appear bluish-green and remain green longer than healthy ones. The glumes spread apart, revealing the "bunt balls" instead of healthy grains. These balls contain millions of spores and release a distinctive, fishy odor caused by trimethylamine, which is a key diagnostic feature in the field.

Environmental conditions play a critical role in the development of the disease. Cool soil temperatures between 5°C and 15°C during germination are optimal for spore infection. Furthermore, adequate soil moisture facilitates the infection process, while dry conditions during seeding may inadvertently favor the persistence of spores in the soil profile.

Management strategies focus on breaking the infection cycle. The most effective approach is the use of high-quality, certified seeds combined with chemical seed treatments using systemic fungicides. Cultural practices such as optimal sowing depth and crop rotation also help in minimizing the risk of infection by reducing the inoculum pressure in the field.

• Utilizing disease-resistant wheat varieties.
• Applying systemic seed dressings before planting.
• Avoiding deep sowing when soil temperatures are cool.
• Sanitizing agricultural machinery to prevent spore spreading.