Fescue endophyte

Fescue endophyte (Epichloe coenophiala) is a systemic, seed-borne fungal pathogen that resides within the intercellular spaces of tall fescue (Festuca arundinacea). Unlike typical plant pathogens that destroy their host, this fungus maintains a symbiotic relationship, enhancing the host plant's drought tolerance and resistance to insect herbivory.

The fungus primarily affects tall fescue. It spreads vertically through infected seeds and persists in the plant tissue throughout its entire life cycle. Because the mycelium resides deep within the seed embryo, it is virtually impossible to eradicate the fungus from a population once it has been established without replacing the plant material entirely.

Symptomatology is deceptive; infected plants often appear healthier, darker green, and more robust than non-infected counterparts. There are no necrotic lesions or visible fungal structures on the leaves. The true impact of the infection is only revealed through the analysis of chemical composition, specifically the presence of ergot alkaloids.

The agronomic and veterinary significance of Epichloe coenophiala is high due to the production of ergovaline, a potent toxic alkaloid. When consumed by livestock, it leads to 'fescue foot', fat necrosis, and heat stress, significantly hampering animal health and productivity in regions where fescue is a primary forage crop.

Management and prevention involve the utilization of 'endophyte-free' or 'novel endophyte' tall fescue varieties. Novel endophytes are specifically selected strains that provide the host with stress tolerance without producing the toxins harmful to livestock. Regular testing of seed lots is essential for ensuring that farmers do not inadvertently introduce the toxic strain to their pastures.