smuts

Smuts are fungal diseases of grasses and cereal crops caused by smut fungi, basidiomycete fungi in the group Ustilaginomycotina. They are characterized by the production of dark, powdery masses of teliospores that replace viable grain in infected organs. The term covers several pathogens and diseases, most notably corn smut on maize, and smuts of wheat, barley, oats, and sorghum. Examples include Ustilago maydis (corn smut), Tilletia caries and Tilletia foetida (wheat bunt and common bunt), and Ustilago hordei (barley smut). Some smuts also affect sugarcane and rice.

Infection typically occurs during early reproductive development or seed formation. The fungi overwinter as teliospores in plant debris or soil; under suitable moisture and temperature, germination leads to infection of developing floral tissues or seeds. Infected organs swell and develop masses that are later filled with dark teliospores, often replacing the grains. Mature spore masses are readily dispersed by wind, rain, or mechanical means, enabling disease spread within fields and to new regions.

Management relies on reducing inoculum and protecting hosts. Practices include the use of resistant cultivars when available, crop rotation and removal of infected residues to reduce soil-borne inocula, cleaning seed and equipment, and timely planting and harvesting. In some crops, seed treatments or foliar fungicides may be used as part of an integrated approach.

Notes: The word “smut” also appears in other contexts, but this article focuses on the plant-pathogenic fungi commonly referred to as smut fungi.