Ohio State University Extension
Department of Horticulture and Crop Science
2021 Coffey Road, Columbus, Ohio 43210-1044

Fescue Toxicosis

AGF-008-92

Tall fescue is one of the most important grass species in the U.S. and is grown on an estimated 35 million acres throughout the country. It is a cool season perennial grass adapted to a wide range of soil and climatic conditions, being tolerant of poor drainage, yet is one of the more drought resistant grasses. Tall fescue will persist on low pH, low fertility soils, however, responds with greater production when limed, fertilized and managed. It is tolerant of continuous close grazing and makes more growth at low temperatures than other cool season grasses. In Ohio the suggested use has been to extend the grazing season into early spring and late fall-early winter in a pasture program. Summer growth may be accumulated (stockpiled) for winter grazing on these areas, a procedure of primary interest and use among beef cow-calf producers. Tall fescue is a sod forming grass which can withstand much traffic and animal tramping.

Determinations of forage quality such as crude protein, fiber, soluble carbohydrates, dry matter digestibility and minerals indicate tall fescue is of high quality and should result in good animal performance. However, livestock producers frequently observe disorders in animals consuming tall fescue. This grass often has been criticized for causing poor animal performance and other livestock health problems. Fescue toxicosis is the term used to describe these adverse symptoms with animals. A toxin within the plant was often suspected as its cause.

Animal symptoms associated with fescue toxicosis include reduced rate of gain or loss of weight, reduced milk production (agalactia), rough hair coat, low feed intake, panting, high rectal temperatures, and excessive salivation. Agalactia has usually been most associated with mares and therefore is of primary importance to horse producers and owners.

New Discoveries

Research in the mid-1970's discovered an endophytic fungus that can grow within tall fescue. An endophyte is a plant which grows within another plant, in this case a fungus growing within the fescue plant. This fungus, acremonium coenophialum, has been shown to be associated with the occurrence of alkaloids in this species. These alkaloids are toxins that relate to summer slump syndrome and fescue toxicosis. Research has shown that cattle birth weights and weaning weights can be increased and beef gains nearly doubled on endophyte-free tall fescue.

The endophytic fungus grows between the plant cells, overwintering in the lower perennial plant parts. In the spring fungal growth closely parallels tiller growth advancing to the flower and seed head, where infested seed is produced. The primary method of transmitting the fungus is through infected seed.

It is speculated that the first tall fescue established in the U.S. was by sowing infected seed from Europe. The highly popular Kentucky 31 variety has been shown to be infected. A survey of 200 fescue fields in Kentucky has shown that 97% were infected. Recent analysis of Ohio tall fescue samples averaged 56 percent infected plants with levels of infection ranging from 0 to 100%. It appears fields planted with infected seed produce infested plants related to the percentage of seed containing viable fungus. Field to field and plant to plant movement of the endophyte is very negligible. This is limited to instances where live seed is physically dispersed to another area or contained in voided manure and results in new plants developing.

What Can Be Done To Established Fescue?

1. A major effort should be made to incorporate legumes into the fescue, the more the better. Even small amounts of legumes increase livestock gains and conception rates even with infected fescue stands.
2. Maximize the use of fescue pastures during the cooler periods of the year, early spring, fall and early winter.
3. During the summer months avoid grazing fescue as much as possible. When it is necessary to graze in summer, only graze for short periods of 7-10 days and then move livestock to other non-fescue pastures.
4. Never permit livestock to graze fescue seed heads. Harvest fescue for hay prior to heading. Remember the fungus tends to concentrate near the seed head and on the seed.
5. The diet of the animals should be supplemented with pasture and hay of other species so that tall fescue is not the primary forage of the animals during the entire year.
6. Infected fields may need to be destroyed and reseeded with endophyte-free fescue seed or with other grass species. Destruction and reseeding is especially important with dairy cattle since infection levels even below 10% can cause severe milk production losses.

Treatment of plants with systemic fungicides has not been successful with the materials tested to date. Research is continuing in a number of states on both foliar and seed treatment.

How To Determine If The Endophyte Is Present

This organism grows within the tall fescue tissue and thus cannot be detected without laboratory testing. OSU does not provide a testing program; however, Auburn University conducts a laboratory analysis and accepts samples from other states. Tillers are most commonly tested, but seed and seedheads also can be evaluated.

Obtain AT LEAST 30 tillers from different fescue clumps selected at random within each field. Tillers should not have formed seed heads. Do not include roots or soil. In mixed stands, be careful not to collect ryegrass or other grass species. Cut the roots off each tiller and strip off any dying outer sheath material. Snip off most of the first leaf blade but leave approximately 1/2 inch. Then snip off any emerged stem growth above this lowest leaf.

Wash and blot dry and separately package each sample group of 30+ tillers in a small plastic bag, mail samples with check for $25.00 per sample payable to:

Ship samples Monday or Tuesday via first class or priority mail in order for samples to arrive in good condition. Results and interpretive information will be received directly from Auburn University.

If seedheads have formed, the Auburn Lab can also test groups of 30+ stem tissue samples cut three inches below the panicles.

Endophyte Free Seed

Seed which is produced from endophyte free plants is fungus free. Advancements have been made in breeding and selection of fungus free plants. Several varieties have been tested and labeled for endophyte content. They are sold as endophyte-free or low- endophyte varieties. Varieties available include A.U. Triumph, Cajun, Endo-Free, Fawn, Forager, Johnstone, Kenhy, Martin, Mozark, Phyter and Safe.

It is interesting to note the endophyte declines with time in stored seed at a rate faster than normal decrease in tall fescue seed germination. Research indicates seed storage for 18 to 24 months will almost eliminate viable endophyte in the seed.

Prepared by:
Landon H. Rhodes
Extension Plant Pathologist

John Underwood
District Agronomy Specialist