Grass Choke Disease

IUCN Red List

not listed

NatureServe

not listed

Minnesota

not listed

Epichloe is a genus of fungi that live as endophytes (organisms that live within the plant’s tissues) in grasses. The species within this genus are classified into three types based on their relationship with the host plant. Types II and III are largely mutualistic, providing benefits to the grass such as increased resistance to pests and drought. Type I species are pathogenic; they form a reproductive structure called a stroma that physically “chokes” the grass, preventing the plant from flowering and producing seeds. Epichloe typhina is a Type I species.

Epichloe typhina is native to Europe, and it has been introduced in North America. It now occurs in the United States and southern Canada from the East Coast through the Great Plains and in the Pacific Northwest, with scattered populations in between.

Epichloe typhina has no official common name, though it is frequently referred to as Choke or the Choke Fungus. These names are derived from Grass Choke, the disease the fungus causes when its visible growth prevents the emergence of the grass seed head. While many of the 40+ species in the Epichloe genus are host-specific to a single grass genus, E. typhina is notable for its broad host range, infecting many different genera of cool-season grasses. In Minnesota, common hosts include bluegrasses, orchard grass, perennial ryegrass, timothy, and wood millet.

When it first appears, the fungus forms a smooth, white, waxy or felt-like cylindrical collar—known as a stroma—around the sheath of the uppermost leaf. During this early stage, the fungus is producing asexual spores (conidia).

As it matures, the stroma changes significantly, turning golden yellow to bright orange. The surface becomes noticeably granular or “bumpy” as the fungus develops tiny, pin-point fruiting bodies (perithecia) for sexual reproduction.

Later in the season, the mass turns dark brown or grayish-brown and may appear weathered or cracked as it begins to decay. This recognizable structure typically measures 1″ to 3″ (2.5 to 7.5 cm) in length and completely encases the developing seed head. By physically “choking” the grass in this manner, the fungus prevents the inflorescence (panicle) from emerging, which renders the plant sterile.

Similar Species

Cool season grasses, including bluegrasses (Poa spp.), perennial ryegrass (Lolium perenne), orchard grass (Dactylis glomerata ssp. glomerata), timothy (Phleum pratense ssp. pratense), wood millet (Milium effusum),

Season