Ryegrass bunt

Pathogen and disease type. Ryegrass bunt is a fungal disease caused by Tilletia lolii, a member of the Tilletiaceae family. It is classified as a smut disease, characterized by the replacement of the plant's seeds with a mass of teliospores. This pathogen is highly specific to certain grass species and primarily affects the reproductive structures of the plants.

Affected crops. The disease primarily infects ryegrass species, including perennial ryegrass (Lolium perenne) and Italian ryegrass (Lolium multiflorum). It is a significant issue for seed production fields and permanent grasslands, where the presence of the pathogen can reduce both the quantity and the commercial quality of the harvested seed.

Symptoms and signs. The characteristic symptoms appear during the heading stage. Infected spikelets are typically stunted or deformed, with glumes splayed outward. Inside these modified spikelets, the normal caryopsis is replaced by a black, powdery mass of spores, often referred to as a "bunt ball." Affected plants may also exhibit subtle changes in overall vigor.

Conditions for development. Infection occurs mainly during the flowering period. Teliospores carried by wind or rain splash land on the stigma of the grass flower, germinate, and infect the developing ovary. The pathogen can survive for several years in the soil or on seed surfaces, making environmental management and initial seed health critical for preventing outbreaks.

Harmfulness and control measures. Ryegrass bunt causes direct economic losses by decreasing seed yield and germination rates. Management strategies focus on preventive actions: using certified disease-free seeds, applying effective fungicide seed treatments, and adhering to strict crop rotation practices. In established fields, early harvesting or mowing before spore release can limit further disease spread.