Epichloe

Epichloe is a genus of ascomycete fungi that are well-known as systemic endophytes of grasses. While some species maintain a mutualistic relationship with their hosts, others act as pathogens causing the characteristic condition known as "choke disease," which fundamentally alters the development and survival of the host plant.

The disease primarily impacts various grass species, including fescues, ryegrass, and bluegrass. These grasses are essential components of pastures, turf lawns, and seed production fields. The economic impact is felt most acutely in seed production, where infection directly results in sterility and significant yield reduction.

The hallmark symptom of Epichloe infection is the development of a white, felt-like fungal stroma that wraps around the stem just below the emerging inflorescence. This physical barrier prevents the head from pushing out properly, leading to distortion, stunted development of the spike or panicle, and ultimately, the failure to produce viable seeds.

The spread of the disease is facilitated by a combination of vertical transmission, where the fungus grows through the seed embryo, and horizontal transmission via airborne ascospores produced on the stroma. Favorable environmental conditions for spread include periods of high humidity and moderate temperatures during the grass's rapid growth phases in spring and early summer.

Managing Epichloe involves a multifaceted approach, starting with the use of certified pathogen-free seeds. Once the fungus is systemic within the plant tissue, it is difficult to eradicate. Therefore, preventative measures include chemical applications during early tillering, rigorous crop monitoring, and the removal of infected host grasses in the vicinity of production fields to prevent secondary infection.

• Utilizing endophyte-free or certified seed stocks.
• Systemic fungicide applications during active growth.
• Isolation of seed production fields from wild grasses.
• Regular inspection for stroma formation in spring.