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The Tall Fescue Endophyte Story

Tall fescue (Festuca arundinacea Schreb.) is the most important cool-season grass in the United States, providing the primary ground cover on some 35 million acres. It is a versatile perennial used for livestock feed, various turf purposes, and for erosion control. Commonly referred to as simply "fescue", this widely adapted, persistent grass is easy to establish, tolerant of a wide range of management regimes, and produces good forage yields. Laboratory nutritive analyses of fescue compare favorably to those of many other cool-season grasses.

The story of tall fescue is truly remarkable. Much has been written about fescue, but often these writings have either been very technical or narrow in scope. This publication is an attempt to provide a readable, unbiased review of the use of tall fescue as a forage grass in the United States during the past sixty years.

Early Historical Developments

Our understanding of the problems and opportunities inherent in using tall fescue as a forage crop has developed at an erratic pace. Many people, including livestock producers, industry personnel, and scientists at many locations have made contributions which have brought us to our current level of knowledge. However, three occurrences deserve special mention.

First, in 1931, Dr. E.N. Fergus of the University of Kentucky visited the W.M. Suiter farm in Menifee County, Kentucky and observed a tall fescue ecotype growing on a mountainside pasture. Being impressed with it, Dr. Fergus collected seed, and the ecotype was subsequently tested at many locations in Kentucky. This led to the release of 'Kentucky 31' in 1943 (the "31" referring to 1931). This variety occupies the bulk of the tall fescue acreage in the United States.

The new fescue variety was vigorously promoted by University of Kentucky Extension Agronomist William C. Johnstone, and was quickly accepted by Kentucky farmers. During the 1940's and 1950's there was phenomenal interest in, and widespread planting of, this grass throughout the lower Midwest and a large portion of the South. In much of the South, fescue filled a void where no other cool season perennial forage grass was adapted.

Unfortunately, this new grass was not without its shortcomings. Its forage was of relatively low palatability to livestock, and performance of animals grazing it was erratic and often disappointingly low. In addition, cattle grazing fescue occasionally developed lameness and sometimes lost portions of their feet or tails during fall and winter. The term "fescue foot" was used to refer to this serious, although relatively infrequent, problem. Another problem noted was termed "fat necrosis" and involves deposits of hard fat in the abdominal cavities of cattle. This problem is associated with heavy application of broiler litter or nitrogen fertilizer to fescue pastures.

In addition, cattle grazing fescue often developed a chronic unthrifty condition, especially apparent during the summer months. This condition came to be widely referred to by the terms "summer syndrome", "summer slump", "fescue toxicosis", or "fescue toxicity". Furthermore, mares grazing tall fescue pastures often aborted, produced stillborn foals, had thickened or retained placentas, or produced an inadequate quantity of milk. For many years these problems remained a mystery, despite vigorous research efforts.

A second historic development involved cattle herds grazing separate fescue pastures on the A.E. Hays farm near Mansfield, Georgia. Only one of the herds exhibited fescue toxicity symptoms. Dr. Joe Robbins and Dr. C.W. Bacon, U.S.D.A, Athens, Georgia, began searching for an explanation for this situation in 1973. Finally, in 1976, the toxic pasture was found to be 100% infected with an endophytic fungus, while the non-toxic pasture was less than 10% infected. This implied an association between the endophyte and fescue toxicity.

A third development involved a grazing experiment initiated in the mid-1970's at Auburn University. Dr. Carl S. Hoveland and co-workers noted marked differences in the appearance and gains of steers grazing newly-established paddocks of fescue on the Black Belt Substation near Marion Junction, Alabama. Ultimately, it was found that there was no fungus infection in paddocks where performance was good, but a heavy infection in paddocks producing poor gains. Thus, the association of the endophyte with poor performance of cattle was documented in a replicated, highly controlled grazing experiment (Table 1). It is believed that some paddocks were endophyte-free because they had been established with old seed in which the fungus had died prior to planting.

Table 1. Grazing days, beef gain/acre, average daily gain, and gain/animal of steers grazing A. Coenophialum-infected and non-infected tall fescue pastures, Marion Junction, Alabama 1978-82.

Tall Fescue Pasture

Animal Days/acre

*Beef Gain (lbs./acre)

Avg. Daily gain (lbs.)

Gain/steer (lbs.)











* Adapted from: C.S. Hoveland and co-workers. Steer Performance and Association of Acremonium coenophialum fungal Endophyte on Tall fescue Pasture. Agron. J. 75:821-824. 1983.

The terms "fescue fungus", "endophyte", "fungal endophyte", and "fescue endophyte", have all been used to denote the organism in question. "Endo" (within) plus "phyte" (plant) means a plant that lives within another plant. In this case, the plant (endophyte) is a fungus, originally identified as Epichloe typhina and later renamed Acremonium coenophialum. It is generally accepted that these terms refer to the same organism.

Two characteristics of the endophyte have great practical importance. First, the organism does not affect either the growth or appearance of the grass, and it requires a laboratory analysis to detect its presence. Secondly, it is seed transmitted and apparently not transmitted in any other way. Thus, once a non-infected stand is established, it can be expected to remain that way.

Endophyte Effects

Animal Response - Studies with animals consuming endophyte-infected fescue have shown the following responses in comparison to animals grazing non-infected fescue: (1) lower feed intake; (2) lower weight gains; (3) lower milk production; (4) higher respiration rates; (5) higher body temperatures; (6) rough hair coats; (7) more time spent in water; (8) more time spent in the shade; (9) less time spent grazing; (10) excessive salvation; (11) reduced blood serum prolactin levels; and (12) reduced reproductive performance. Some or all of these responses have been observed in numerous studies in dairy cattle, beef cattle, and sheep consuming endophyte-infected pasture, green chop, hay and/or seed.

The initial steer grazing study at Auburn University showed an 82% increase in average daily gain (ADG), and 42% increase in gain per acre with endophyte-free fescue compared to endophyte-infected fescue (Table 1). Interestingly, gains were reduced throughout the grazing season, and not just in the summer. Other grazing studies with steers in Kentucky, Alabama, Georgia, Missouri, Texas, Tennessee, North Carolina, and Maryland have also shown ADG's 50 to 100% greater on low-endophyte, as compared to high-endophyte, tall fescue pastures.

Presence of the endophyte affects grazing livestock in many ways. In Georgia, Stuedeman and co-workers found that steers on low-endophyte fescue grazed 43 to 65% of the time between noon and 4:00 p.m., while steers on high-endophyte fescue grazed only 5 to 21% of the time during the same period. Steers moved from high- to low-endophyte fescue did not resume normal grazing habits for 26 days, indicating a residual effect. H.W. Essig at Mississippi State University found that the body temperatures of cattle did not return to normal until 56 days after removal from infected fescue. Other studies in Alabama and Kentucky have shown increased gains, increased intake, and lower body temperatures of steers consuming endophyte-free seed or hay when compared to animals consuming infected seed or hay.

Research conducted by University of Kentucky scientists Drs. R. Hemken, J. Boling, and colleagues revealed a 39% reduction in forage intake and a 37% decrease in milk production during summer in lactating dairy cows consuming endophyte-infected fescue. In addition, these cows lost weight, while animals consuming non-infected fescue gained weight.

Dr. Nelson Gay and associates in Kentucky found that beef cows had a 34% lower pregnancy rate when grazing highly infected, as compared to endophyte-free, fescue pastures (Table 2). Similar responses have been found in Missouri. Furthermore, Drs. S.P. Schmidt and D.A. Danilson at Auburn University observed a sharp drop in pregnancy rates of replacement beef heifers grazing infected fescue, almost in direct proportion to the level of endophyte infection (Table 3). Several other studies have shown sharply reduced milk production of beef cows grazing infected fescue.

In studies with horses, Drs. J.L. Monroe, D.L. Cross and others at Clemson University found that grazing pregnant mares on infected, compared to non-infected fescue, increased the number of stillborn foals, agalactic mares, and retained placentas. It also decreased the number of mares which rebred after foaling.

Table 2. Pregnancy Rate in Beef Cows



Low Endophyte Fescue


High Endophyte Fescue




N. Gay and co-workers, University of Kentucky, 1986 (3 years)


Table 3. Effect of Fungus-Infected Tall Fescue Pastures on Growth and Reproduction on Replacement Beef Heifers at Two Locations (Black Belt and Tennessee Valley Substations) in Alabama, 1984-86*

Fungus Level












* Adapted from: S.P. Schmidt and co-workers. Fescue Fungus Suppresses Growth and Reproduction in Replacement Beef Heifers. Highlights of Agricultural Research Vol. 33, No. 4, Winter 1986. Ala. Agric. Exp. station.

Endophyte Distribution - Over 90% of the tall fescue fields tested in the United States contain the endophyte. In Kentucky, over half the plants were infected in 83% of the fields sampled, and over half the fields had 80% or higher infection levels. A 1985 Illinois survey showed an average infection level of 78%.

Dr. Richard Shelby, Directory of The Fescue Diagnostic Center at Auburn University, reports that his facility has tested several thousand producer-submitted samples from 28 states and several foreign countries, 91% of which had some level of infection. The average infection level for these samples was 62%, with a range of infection from 0 to 100%.

Therefore, since most fescue fields are endophyte-infected, most producers who use fescue as a forage grass are not obtaining the level of animal performance which would otherwise be possible. A relationship between level of infection and animal performance among animal species and classes has not been established. However, data from Alabama, Missouri, and Kentucky suggest that each 10% increase in endophyte level can result in a reduction of 0.1 pound in ADG of growing beef animals.

Research in many states has demonstrated conclusively that the fescue endophyte is associated with negative effects on animal performance. The mechanism is as yet unknown, but a toxin is strongly suspected. Regardless, the economic impact of this problem is immense, perhaps exceeding $500 million annually in terms of lost beef gain alone!

Potential Adverse Aspects

Several years ago, G.C.M. Latch and other scientists in New Zealand found that an insect called the Argentine stem weevil would devastate endophyte-free, but not endophyte-infected, perennial ryegrass. This insect is not a pest in the U.S., but this knowledge is disquieting since the endophytes in the two grasses are closely related.

In addition, Dr. Reed Funk and associates in New Jersey found that sod webworm damage is greater on endophyte-free, than with endophyte-infected, turf-type fescues. No field research to date has shown increased damage by insects to endophyte-free forage fescue planting, but greenhouse work in Alabama and Kentucky has shown that aphids prefer endophyte-free fescue. Tests in Louisiana and Georgia revealed reduced survival, growth, and development of fall armyworm larvae fed endophyte-infected fescue. Dr. M.R. Siegel at the University of Kentucky found evidence that alkaloids in endophyte-infected fescue are associated with increased resistance to insect feeding. A greenhouse study by Dr. J.F. Pedersen at Auburn University revealed over three times as many spiral nematodes associated with the roots and soil of endophyte-free, than of endophyte-infected, fescue plants.

Furthermore, grazing livestock prefer endophyte-free over endophyte-infected fescue. If given the choice, they will spend far more time grazing endophyte-free fescue, and their intake will be greater, thus requiring a lower stocking rate.

An apparent difference in vigor has sometimes been observed between infected and non-infected pastures in some environments. This has usually been seen only in new plantings, but in tests conducted in stressful environments, by Dr. Richard Joost in Louisiana and by Drs. J.C. Read and B.J. Camp in Texas, stand loss was greater in established endophyte-free pastures.

These findings have important implications. First, while fescue is regarded as a forage crop which is easy to establish, that may be less accurate when the fescue is endophyte-free. Thus, when establishing endophyte-free fescue, a producer should carefully follow all recommendations, including time of planting, fertilization, etc.

Secondly, since overgrazing is more likely to occur when the endophyte is not present, endophyte-free fescue requires a higher level of grazing management. In particular, overgrazing should be avoided during the establishment year or in highly stressful environments.

In addition, severe stress may be more likely to result in stand decline in established stands of endophyte-free fescue. Thus, fields which are only marginally adapted to fescue probably should not be planted to endophyte-free fescue.

Finally, while insects and other pests do not currently limit the use of endophyte-free fescue, it is possible that pest problems may be greater with endophyte-free fescue. It may be advisable to monitor such pastures more closely in the hope of eliminating any such problems before they cause serious damage.

Relatively little information is available regarding long term stand persistence of endophyte-free fescue. However, endophyte-free fescue stands at the Auburn University Black Belt Substation have persisted and remained endophyte-free for over 10 years though separated from infected fields only by a barbed wire fence.

Based on current knowledge and experience, with the exception of highly stressful situations, endophyte-free fescue can be expected to persist well. However, even if periodic re-establishment became necessary, the improved animal performance on endophyte-free pastures would easily justify re-establishing a highly infected field. Despite the need for somewhat higher management levels, the opportunities provided by endophyte-free fescue are great.

Strategies for Coping With the Endophyte

Livestock producers who have, or who plan to establish, fescue fields should develop an intelligent "endophyte strategy" based on research findings. The following is a review of options available for avoiding or minimizing endophyte effects.

Establishing New Fescue Stands

When planting a new fescue field, a livestock producer should use seed known to have little or no (certainly less than 5 percent) endophyte infection. In a few states, fescue seed tags must state the percent endophyte infection. The importance of knowing the level of endophyte infection in seed can hardly be overemphasized. For example, when a beef producer uses endophyte-free seed, it can increase returns by $75.00 or more per acre per year at current beef prices. This increased beef production can be expected every year for the life of the stand!

New fescue plantings, even if endophyte-free, should normally include a legume. Kentucky research indicates that clover in an endophyte-free fescue stand will further increase young animal gains by 0.2 pounds per animal per day. However, the primary justification for planting a legume with fescue is that it can result in 2 or more years of excellent animal performance with little or no nitrogen fertilizer expense.

White clover (preferably a Ladino type), seeded at the rate of 2 to 4 pounds per acre, is the best clover companion in most fescue pastures. However, red clover, at a rate of 10 to 15 pounds per acre broadcast or 8 pounds per acre drilled, is another good possibility, especially when fields are to be cut for hay. Other legumes such as birdsfoot trefoil or alfalfa may also be useful in certain situations.

Dealing With Existing Endophyte-Infected Seeds

Producers with established fescue fields need to carefully assess their situations. Existing fescue stands should be tested on a field-by-field basis. Several states now have laboratories for determining endophyte level. County agricultural agents can provide information regarding cost, sampling methods, and laboratory addresses.

Once the level of endophyte in existing fescue pastures is known, a producer can select the best option for dealing with the problem. The best way to handle one field may not be best for another. Four general approaches are available.

1. Manage to minimize the effect - Endophyte effects on animals can be minimized with management practices. Grazing and/or clipping management that keeps plants young and vegetative will result in better animal performance. Likewise, if fescue is cut for hay in the boot stage, better animal performance will be obtained than from late-cut hay. Other practices such as chain harrowing, fertilizing, pest control, creep grazing, and rotational grazing will result in improved overall pasture quality and animal performance.

2. Avoid the Endophyte - Use of other forage species avoids the endophyte. Using infected fescue in spring and fall with other grasses or grass-legume mixtures for summer grazing will avoid the endophyte during the summer when fescue forage quality is low. Since animal performance is adversely affected by feeding infected fescue hay, feeding of hay of another species can also be helpful.

3. Dilute the Endophyte - The endophyte or its products can be diluted through the use of other feeds in the diet. Growing legumes with infected fescue is an attractive option. Many studies have shown increased pasture production, higher liveweight gains, and improved pregnancy rates when pastures are renovated to include legumes.

4. Kill infected stands and replant - Low-endophyte or endophyte-free seed is now readily available in most areas of the United States where fescue is grown. Several excellent new varieties of fescue have recently been released, and others are expected. Careful consideration should be given to choosing low-endophyte seed. However, a new variety that is simply "low-endophyte" or "endophyte-free" will be of little or no value if it is not productive in the area in which it is to be grown. When selecting a variety, attention should be given to adaptation, agronomic performance, animal performance, persistence, and pest resistance. The best source of variety information is university variety trials.

The cost of converting from high- to low-endophyte fescue varies. Where fescue is used in rotation with other crops, the only difference in cost will be the small price difference between low- and high-endophyte seed. Where the sod is killed with a herbicide and the seed drilled into the killed sod, the cost may be $30 to $50 per acre. Where existing fescue is destroyed by tillage and immediately replanted, the cost may be as high as $100 or more per acre.

Any infected fescue field which is to be replanted should not be allowed to produce seed during the re-establishment year. Seedhead formation should be prevented by heavy grazing, clipping, or by chemical application. This is for the purpose of preventing seed production which could lead to the establishment of volunteer infected plants.

Under usual storage conditions, the endophyte will die within one or two years. Thus, any volunteer plants from old seed will usually be endophyte-free or have a very low level of endophyte infection. Unfortunately, the germination level of fescue seed may drop sharply during long term storage, depending on temperature and humidity conditions. Furthermore, the vigor of seedlings resulting from planting old seed is likely to be reduced.

Methods of replacing endophyte-infected stands include:

A. Rotation - Rotating with other crops, followed by seeding low-endophyte fescue, is an excellent approach. There are many options ranging from no-till corn or a summer annual grass to longer term rotations involving a perennial such as alfalfa or two or three annual crops. With any rotation option, careful consideration must be given to herbicide residues, erosion hazards (leave all waterways - it's better to have a highly infected sod waterway than a non-infected gully), and complete destruction of the old fescue.

B. Prepared Seedbed - Certain situations permit destroying the old sod through tillage, preparing a seedbed, and then replanting non-infected fescue. However, it is often difficult to completely destroy an old fescue sod by tillage.

C. Chemical Kill No-Till - Where methods A and B are not feasible, chemical kill of infected stands following by no-tillage planting is the only remaining option. This technique can be used to go directly from infected fescue to non-infected fescue, or other forage crops can be used in a rotation. It is critical that chemicals be used effectively, thus killing all the existing infected fescue. Furthermore, in some cases there may be common bermudagrass or other species which must also be killed, requiring the use of more than one herbicide or a higher herbicide rate. Effective sod kill requires attention to label instructions and striving for optimum environmental and plant conditions that will permit greater chemical effectiveness. Consult state recommendations on chemicals, rates, and time of application.

Best results from no-till tests have been found with late summer or early autumn seedings of fescue. Although chemical kill has been satisfactory in spring, summer drought and competition from warm season annual weeds tend to reduce stands of spring-seeded fescue.

A particularly effective approach is to use no-till plantings of annual forages after killing infected fescue. For example, infected fescue can be chemically killed in the spring and a summer annual grass can be drilled into the killed sod, followed by no-till planting of non-infected fescue in the fall. Similarly, fescue can be killed in the fall followed by sod planting of winter annuals and, if desired, sod planting of a summer annual grass the next spring. In this case, non-infected fescue would be planted one year after the infected fescue was killed. Use of annuals in this matter "smothers" fescue plants which escaped the chemical treatment and also reduces the likelihood of insects in the old fescue sod damaging seedling fescue plants.

Current Outlook

Discovery of the fescue endophyte constitutes a breakthrough of monumental proportions. Most scientific advancements come in small increments. In this case, we are seeing a dramatic increase in the performance of animals grazing a tough, widely-adapted perennial grass. Despite some potential disadvantages, the proper establishment and management of endophyte-free fescue constitutes an unprecedented opportunity for thousands of livestock producers to obtain animal performance far superior to what they would obtain by establishing, or keeping, endophyte-infected stands.

Furthermore, there are many endophyte-related studies in progress, including several aimed at developing a better understanding of fescue foot, fat necrosis, and horse reproductive problems. Future discoveries may answer remaining questions relating to this problem, and perhaps provide additional solutions. It seems clear that application of the existing and forthcoming technology relating to this breakthrough will have an immense impact on livestock production in the fescue-growing region of the United States, and perhaps in many other parts of the world.

Prepared by Donald M. Ball, Garry Lacefield, and Carl S. Hoveland. Dr. Ball and Dr. Lacefield are Extension Forage Crop Agronomists at Auburn University and the University of Kentucky, respectively; Dr. Hoveland is Professor of Agronomy at the University of Georgia. Funding for this publication was provided by the Oregon Tall Fescue Commission, Salem, Oregon.