Cause Neotyphodium coenophialum and N. lolii are fungi that grow within tall fescue and perennial ryegrass, respectively. The name endophyte describes this life habit of the fungi. Natural transmission occurs only by planting endophyte-infected seed; no transmission from infected to uninfected plants has been observed in nature. Both plant and fungus benefit from the relationship. Benefits to the host include enhanced seed germination rate, increased seedling vigor, improved drought tolerance, greater persistence, toxicity to certain herbivores, increased resistance to insects, and reduced disease severity with some, but not all, pathogens. Benefits to the fungus include host nutrition, protection, and a method for dissemination. Obviously, the presence of the endophyte can be positive or negative depending on whether an improved variety is used for forage or turf.
Symptoms Fungi grow within the host without showing any sign or symptom of infection. Both fungi can produce alkaloids toxic to cattle, sheep, and other livestock; eating endophyte-infected seed, hay, or infected pasture grass can result in toxicosis. The amount of alkaloids produced varies with environmental conditions during plant growth.
Sampling Methods to detect endophytes in leaf sheaths, crowns, meristems, and tillers include staining tissue and microscopically examining freshly produced seed, growing seedlings from stored seed, and immunological procedures. Methods also are available to determine the concentration of the compounds responsible for livestock toxicosis, ergovaline in tall fescue and lolitrim B in perennial ryegrass. The Oregon Department of Agriculture tests for endophyte in seed only. The OSU Seed Lab assays seed, seedlings, and vegetative plants for a fee.
Cultural control Have plants tested. Feeding or grazing endophyte plant residue must be done with extreme caution.