Neotyphodium

Neotyphodium is a genus of fungal endophytes that live symbiotically within the tissues of grasses. While many species have been reclassified under the genus Epichloë, the term remains common in agronomic literature. Unlike pathogenic fungi that destroy host tissues, these endophytes exist within the intercellular spaces of the plant throughout its entire life cycle.

These fungi typically colonize perennial grasses, including tall fescue and perennial ryegrass. The infection is often invisible, meaning there are no necrotic spots, wilting, or other standard signs of plant disease. Instead, the fungus may provide the host plant with increased drought tolerance and resistance to some insect pests.

The primary agricultural concern is the production of alkaloids, such as ergovaline and lolitrem B. These compounds are toxic to livestock, causing conditions known as "fescue toxicosis" or "ryegrass staggers." Symptoms in animals include tremors, hyperthermia, reduced weight gain, and in severe cases, gangrenous necrosis of limbs.

The development and spread of Neotyphodium are primarily vertical, occurring through infected seeds. Once a grass stand is infected, the fungus persists through every generation of the plant. Environmental factors that promote healthy grass growth generally favor the survival and metabolic activity of the endophyte.

Effective control measures focus on preventive management. Farmers should exclusively use "endophyte-free" certified seed to establish new pastures. If toxicosis is suspected, forage analysis for alkaloid levels is necessary. In some cases, replacing infected stands with endophyte-free cultivars is the only reliable way to eliminate the risk to livestock.