ALTERNATIVES FOR FUNGUS INFECTED TALL FESCUE
Garry D. Lacefield and Jimmy Henning
Department of Agronomy
Tall fescue (Festuca arundinacea Schreb.)
is the most important cool-season grass grown in the United States, providing
the primary ground cover on approximately 35 million acres. Adapted to
a wide range of soil and climatic conditions, it is used for livestock
feed, lawns, turf and conservation. Tall fescue is relatively easy to establish,
persistent, and relatively free of disease and insect pests. It produces
high dry matter yields when properly fertilized and compares favorably
to many other cool-season grasses in its chemical analysis.
In 1931, Dr. E.N. Fergus, University
of Kentucky Agronomy Department, collected seed from an old tall fescue
field in Menifee County, Kentucky, and after extensive statewide testing,
the variety Kentucky 31 was released in 1942. This variety now occupies
the majority of U.S. fescue acreage.
Despite the many positive attributes
of this grass, several features of Ky 31 have been less than ideal. Animal
performance on Ky 31 has been erratic and often less than what producers
and researchers desire. Ky 31 has relatively low palatability and "something"
occasionally leads to lameness of cattle grazing tall fescue. Also, "fat
necrosis," (the presence of masses of hard or necrotic fat, primarily in
tissue of the abdominal cavity) has been associated with cattle grazing
tall fescue pastures heavily fertilized with broiler litter. "Summer syndrome,"
"summer slump," "fescue toxicity" and "fescue toxicosis" are terms widely
used to denote poor performance by animals grazing tall fescue during the
Endophytic Fungus Discovered
In June 1973, Dr. Joe Robbins, USDA,
Athens, Georgia, visited the Hays farm at Mansfield, Georgia and observed
fescue pastures being grazed by two separate herds of cattle. One herd
exhibited many of the symptoms associated with summer syndrome, while cattle
in the adjacent pasture appeared healthy with no summer syndrome. During
the next three years Dr. Robbins and Dr. C.W. Bacon examined pastures on
the Hays farm in search of a causative agent of summer syndrome. In 1976,
plants from the poor-performing pastures were found to be 100% infected
with an endophytic fungus (Acremonium coenophialum) while plants from the
unaffected pasture were less than 10% infected with the endophyte. This
association marked a major breakthrough in finding the cause of the fescue-endophyte-summer
syndrome relationship. Subsequently, fescue samples from research programs
in Kentucky, Maryland, Alabama, Missouri and Virginia were analyzed for
endophyte content. Samples from each state showed poor performing pastures
to be highly infected with the endophyte while better performing pastures
were less than 50% infected.
Subsequent surveys in states within
the fescue region have shown that over 90% of the tall fescue fields which
were sampled contained high levels of the endophyte. Researchers from the
University of Kentucky reported 83% of fescue fields sampled in Kentucky
contained over 50% infection with 53% of the fields over 80% infected.
Animals consuming fescue containing
the endophyte have shown some or all of the following responses: (1) lower
feed intake; (2) lower weight gains; (3) lower milk production; (4) higher
respiration rate; (5) higher rectal temperature; (6) increased water consumption;
(7) rough hair coat; (8) more time spent in shade; (9) excessive salivation;
(1O) greater urine volume; (11) reduced prolactin level; (12) reduced reproductive
performance; and (13) nervousness. These responses have been shown with
animals consuming pasture, hay, silage, green-chop and seed.
Although all of the above responses
are important, weight gain, milk production and conception are of particular
economic significance. Workers at the University of Kentucky showed a 39%
reduction in forage intake and a 27% decrease in milk production during
the summer by lactating dairy cows that consumed endophyte-infected fescue.
Cows consuming endophyte-infected fescue lost weight, while animals consuming
non-infected fescue gained weight.
Similar results have been found in
grazing studies with beef cattle. Although data are not conclusive, it
appears that for every 10% increase in fescue endophyte level, there is
likely to be a reduction of 0.1 lb average daily gain by growing beef animals
grazing such fields.
Reducing or eliminating the endophyte
from the animals diet results in increased performance. Beef production
per acre has been increased from 1/4 to 1 lb/day by reducing or eliminating
endophyte from the diet. The magnitude of the increase depends on several
Additional work is needed to determine
the endophyte effect on reproductive performance. Work in Kentucky shows
a 26% increase in conception rates with beef cows grazing endophyte-free
fescue compared to highly infected fescue pastures. Studies are underway
to more fully determine endophyte effects on reproduction.
Alternative Management Strategies
There is little doubt that the endophyte
is associated with the quality problems long observed in tall fescue, even
though a cause-effect relationship between the endophyte and a toxin has
not been shown conclusively. Research suggests at least three areas that
should be considered to offset or eliminate the endophyte effect in animal
(1) Manage Fescue and Animals to Minimize the Effect
Mature fescue is poor feed. Grazing,
mowing, or use of growth regulators such as mefluidide, to keep plants
young and vegetative will result in better animal performance than grazing
or feeding more mature plants. Likewise, hay harvest in the boot stage
will result in better animal performance than if cut later. Other management
factors such as chain harrowing, fertilizing, pest control, creep grazing
and rotational grazing can result in improved overall pasture management
and animal performance thus minimizing the effects of the endophyte.
Avoid grazing endophyte infected pastures
during critical times. Don't graze high endophyte pastures just before
calving or foaling and just before breeding. If possible, graze other species
for around 60 days after calving. Don't use infected fescue with lactating
Effects of the endophyte can be avoided
simply by using other cool-season grasses, warm-season grasses and/or legumes.
A system of using infected fescue in spring and fall with other grass or
grass-legume mixtures for summer grazing will avoid the endophyte effects
during the most critical summer slump period.
(2) Dilute the Endophyte Effect
Negative effects on animal performance
can be diluted substantially by the presence of other feeds in the diet.
A most practical and economical way of diluting the effect is by growing
legumes with the infected fescue. Research from many states over the years
has shown increased liveweight gains and conception rates when legumes
are a significant component of fescue pastures. Even small amounts of legumes
in endophyte-infected fescue pastures can sharply increase animal gains.
In fact, legumes can give a benefit even in fungus-free pastures.
(3) Replace Infected Stands with Low Endophyte Varieties
Determine the level of infection before
deciding to replace an old stand. Your County Agricultural Agent can give
you copies of PPA-30, Sampling for the Tall Fescue Endophyte in Pasture
or Hay Stands, and can advise you how and when to take samples and where
to send them. Accurate sampling is important. Several low-endophyte or
endophyte-free varieties are now available and additional varieties will
likely become available in the future. Carefully choose a low-endophyte
variety. A new variety that is simply "low-endophyte" or "endophyte-free"
will be of little or no value if it is not adapted to your area, does not
produce well, is susceptible to diseases or other pests, or gives poor
Cost of converting from high to low
endophyte fescue will vary depending on land class and farming programs.
Where fescue is used in rotation with other crops, cost differences will
only be the difference between low and high endophyte seed. If row crop
production is undesirable or impossible, cost of chemicals, fertilizer,
seed and tillage equipment will range from $50 to over $150/acre. It makes
sense to begin replacement of stands on soils which have highest yield
Although many questions remain, the
tall fescue research program has resulted in major breakthroughs. Many
questions still remain to be answered; however, application of the existing
technology will have a dramatic impact on animal agriculture.
Replacing an Infected Stand
Any infected fescue field to be re-established
should not be allowed to mature seed during the reestablishment year. Prevent
seedhead formation with heavy grazing, clipping or chemicals, so that any
seed in the soil will be over one year old when the new low endophyte variety
is seeded. Research has shown that the endophyte dies in seed usually within
a year, so any volunteer plants from old seed would be endophyte free.
The best way to kill an old stand is
to grow corn in the field for one or two years. Use either combinations
of conventional tillage and chemicals or no-tillage with chemicals. It
is very hard to kill all of the fescue with tillage alone. If the no-till
system is used, carefully select chemicals to minimize toxic residue. In
any case, leave the sod waterways. Having heavily infected fescue in a
waterway is better than having a non-infected gully.
On farms where corn is not grown or
on sloping land where row crops are not feasible because of erosion hazards,
chemical kill of infected stands followed by no tillage is the only remaining
option. Chemical kill-no-till can be used to go directly from fescue to
fescue, or other forage crops can be used in a rotation. It is critical
that chemicals be used effectively, to try and kill as much of the existing
fescue as possible. This requires paying attention to label instructions
and striving for optimum environmental and plant conditions that will permit
greatest chemical effectiveness.
Research is underway at different locations
within the fescue belt on chemicals, rates and time of application.