Epichloe sylvatica

Epichloe sylvatica is a fungal pathogen classified as an ascomycete, functioning as a systemic endophyte within various grass species. Unlike typical necrotrophic pathogens, this fungus maintains a symbiotic-like relationship with the host plant during its vegetative stage, colonizing the intracellular spaces of stems and leaf sheaths without causing immediate necrosis.

The primary hosts for this fungus are wild grasses, particularly those within the Brachypodium genus. In an agricultural context, it affects perennial grasses intended for forage and pasture. While it may not kill the individual plant, the fungus severely reduces the overall biomass quality and effectively prevents the plant from producing viable seeds by disrupting the reproductive development.

The most visible symptom of the infection is the development of a fungal stroma during the flowering stage. This stroma appears as a dense, whitish or yellowish mycelial mat that encases the stem. This physical constriction prevents the inflorescence from emerging from the leaf sheath, a condition known as 'choke' disease, which renders the plant sterile and prevents the formation of seeds.

The development and spread of Epichloe sylvatica are heavily influenced by environmental conditions, specifically high humidity levels and mild temperatures. Spores are disseminated by wind and insect vectors, which facilitates the rapid spread across meadow systems. Densely packed vegetation serves as a primary reservoir for the fungus, as restricted airflow maintains the high humidity required for spore germination.

Management strategies for this disease rely on preventive agronomic practices. The most effective approach involves frequent mowing of the forage grasses before the fungus produces its conidia, thereby breaking the cycle of infection. Additionally, ensuring proper field sanitation and avoiding excessive nitrogen fertilization, which can create dense, moisture-trapping canopies, helps to mitigate the severity of the disease and maintains the health of the grassland.