Choke disease

Choke disease, caused by the fungus Epichloe typhina, is a common fungal infection affecting a wide range of forage and amenity grasses. The pathogen is unique in its biological interaction with the host, as it systemically colonizes the plant tissues and manifests physically during the reproductive stage.

The primary host species include orchard grass, timothy, fescue, and bluegrass. The economic significance of this disease is high in the seed industry because the fungal growth directly inhibits the development of the grass inflorescence, significantly reducing seed yield and quality in susceptible stands.

The clinical symptoms are unmistakable: a white or creamy-yellow stroma of the fungus forms a tight collar or "choke" around the stem just below the head. This structure physically prevents the emergence of the seed head, causing the spike or panicle to remain trapped, distorted, and eventually sterile.

Environmental factors, particularly high humidity and cool to moderate temperatures, are the main drivers for the development of Epichloe typhina. The fungus spreads via wind-borne ascospores and can also persist in plant tissues, moving into developing tillers. This systemic nature makes it difficult to eradicate once a field is established.

Management strategies focus on prevention and cultural controls. Growers should prioritize the use of certified pathogen-free seeds to avoid introducing the fungus to new areas. Additionally, early mowing before the fungal stroma produces spores can help reduce the inoculum levels in the field, while systemic fungicides may be used in commercial seed production to protect developing crops.