Choke disease

Epichloe festucae is an endophytic fungus known as the causal agent of choke disease in various grass species. Unlike many pathogens that cause immediate tissue death, this fungus establishes a systemic association within the plant, living in the intercellular spaces. It is unique due to its ability to be vertically transmitted via seeds, ensuring its persistence in subsequent generations of host plants.

The primary hosts for this pathogen are grasses, especially those in the Festuca genus. The fungus colonizes the vegetative tissues and, depending on the specific host-fungus interaction, can shift from a mutualistic relationship to a pathogenic one, where it suppresses the reproductive growth of the grass host.

The characteristic symptom is the development of a white or pale yellow fungal stroma that wraps tightly around the developing inflorescence. This physical obstruction prevents the emergence of the seed head, a condition commonly referred to as choke. Consequently, the affected plants are unable to produce viable seeds, leading to significant yield loss.

The development and spread of Epichloe festucae are heavily influenced by environmental conditions, particularly moisture and temperature. Spore production occurs on the surface of the stroma, and these spores are disseminated by wind or insects, facilitating the infection of healthy plants during the critical flowering stage of the grass cycle.

The threat posed by this fungus extends beyond crop loss to animal health. Infected grasses can produce ergot alkaloids, which are toxic to livestock and can cause serious neurological and physiological distress when ingested. Effective management strategies involve sourcing pathogen-free seeds, implementing strict phytosanitary measures, and removing infected plants from pasture lands to prevent further spread.