Managing tall fescue in pastures


Many pastures in Ohio contain tall fescue as one of the cool-season plants which make up our pasture’s mix. Tall fescue is a persistent perennial bunchgrass that adapts to a wide range of conditions.

It is tolerant of low pH, poor soil drainage and can endure drought situations well. Tall fescue adapts to most Ohio soils and forms a thick deep rooted sod when managed properly.

However, this plant may be reducing your livestock’s production if you are not monitoring its growth.


Most farm managers know tall fescue can be infected with endophyte. Endophyte is a fungus that grows inside a host plant, without causing it any harm. In many cases the endophyte can be beneficial to the host plant making it more vigorous and competitive against other companion species.

The endophyte produces chemicals called alkaloids that help protect the plant against insects and parasitic soil nematodes. Some alkaloids are non-toxic to livestock while others, such as ergovaline, are toxic and they cause poor animal performance and health issues if livestock consume them in too high a quantity.

The combination of health and performance problems caused by endophyte is usually referred to as “fescue toxicosis.” When too much ergovaline is ingested it can cause constriction of blood vessels in animals.


Problems associated with this condition include heat stress, poor weight gains, lower milk production and hormonal imbalances leading to reduced fertility and in severe cases, loss of the animal’s hoof, tail or ears from gangrene.

Reduced potential gain has been documented in beef stockers and other cattle equivalent to 0.1 pound/day for each 10 percent of endophyte infection. Many tall fescue pastures that have been evaluated show greater than 80 percent infection rates.

Why put up with it?

So, why would anyone want this stuff or put up with it on their farm? Well, it’s not easy to eradicate if you already have it growing on your farm, it works well for stockpiling forage for winter grazing, it has a long growing season and it can be managed to reduce toxic effects.

During the fall, tall fescue produces higher yields of stockpiled forage and maintains superior nutrient quality compared to most other cool-season grasses for winter grazing paddocks.

Fall stockpiled fescue is very palatable and also highly digestible (high in soluble sugars) after frosts occur.

What can we do with tall fescue until fall? Understanding how the plant grows and what endophyte does in the plant is helpful.

What happens

Without getting too technical, let’s look at what happens. As mature tall fescue plants re-grow in the spring, cells that will form leaves are already present in the crown of the plant and the endophyte, that can produce ergovaline, is also present.

The leaf cells begin to expand causing growth to occur. When the correct moisture, temperature and sunlight combine, rapid expansion of cells occur and we get what we call the spring flush of grass growth.

Dr. Barker at Ohio State University likens the endophyte in the leaf at this point as a surfer riding along on a wave. It is not growing through the leaves, but ‘riding’ along with cell expansion.

However, the growth at this time can be so rapid that the surfer can’t stay atop the wave and the growth goes on without the surfer/endophyte with it.

This means we have leaves/forage without endophyte in the area the livestock will eat so no toxic ergovaline is present either.

Repeated over and over

This is repeated over and over as the spring flush occurs because temperatures are still relatively cool and the plant is growing so quickly.

Finally, however, seed heads start to show up and endophyte can hang on to the seed better than it could the rapidly expanding leaf cell.

The highest concentration of endophyte occurs in the seed heads so we don’t want the livestock to eat them. Mechanically harvesting, bush-hogging or rotating the livestock to keep seed heads from forming is the goal. Sounds easy, but it requires good management to make this happen.

Temperatures rise

The next problem is temperatures start to rise as we get into June, July and August. Two things happen as a result of this.

Tall fescue growth slows down allowing the endophyte to “ride the wave” to its end as new leaf growth occurs. Also, when temperatures rise above 60 degrees Fahrenheit, the toxic ergovaline starts to be produced by the endophyte fungus and above 80 degrees Fahrenheit, ergovaline production really takes off.

Consumption at this time is what actually causes the summer time problems we mentioned earlier for our livestock. This is where dilution of the tall fescue with other species becomes important.

Having other grasses and legume plants in the pasture sward allows livestock to consume forage that is not loaded with the toxic alkaloid. If you can maintain legumes in these pastures it generally increases weight gain of livestock over pure fescue stands.

Frost seeding 1-3 pounds of red and white clover seed in February or March is the easiest way to re-establish clovers lost from tall fescue.


The struggle for me always becomes the month of June and early part of July. Mowing is generally necessary by this time to eliminate the seed heads. After that, it’s time to start stockpiling the predominantly tall fescue paddocks for winter grazing.

Forage accumulated at that point will not be used until cool weather arrives again and cattle are less subject to heat stress allowing them to perform better.

Less ergovaline is produced again as temperatures decline so toxic effects are minimized.

Best time to apply

Late July or early August is the best time to apply nitrogen to prepare stockpiled tall fescue for winter grazing. As a rule of thumb, 1/2 -1 ton of additional forage may be expected for each 50 pounds nitrogen applied.

So by spreading approximately $20 of urea, 50 pounds actual nitrogen per acre just prior to a rain, a producer may expect 1000 pounds or more of additional dry matter to be produced by the end of the growing season.

Forage stockpiled this way and used in December or January is generally high quality and more than adequate for cows or ewes in mid-gestation.

Samples of stockpiled tall fescue taken in January regularly show 9-13 percent crude protein and approximately 60 percent or more total digestible nutrients.

This is often better than first cutting mixed grass hay made in the June/July time period.

Strip grazing

Maximum utilization of stockpiled forage can only be obtained by strip grazing. You don’t want to place your livestock in a large area and just let them roam over it.

Moving a “hot” front wire every few days to supply the necessary amount of feed for the livestock will reduce waste significantly.

I’ve also found that stockpiled tall fescue areas hold up better to cattle movement in the spring when conditions are wet because of the massive root base under the stockpiled forage.

Two other options

Two other options may benefit producers. One is to renovate pastures and plant endophyte-free tall fescue. Ask your seed supplier for an endophyte certificate showing the endophyte-free status for any new seeding.

Some producers in Ohio have been able to get 62 pound milk per day on endophyte free tall fescue pasture.

The other option is to renovate and plant non-toxic endophyte tall fescue. This is most commonly sold as Max-Q tall fescue, but either of these options runs the risk of having the pastures re-contaminated with toxic tall fescue if precautions are not taken.

Plant of extremes

So, tall fescue is a plant of extremes. While many producers hate it others love it. Although livestock may develop problems from consuming to much toxic endophyte, tall fescue does have many characteristics that can benefit forage producers.

It has few pest problems, it’s hardy in a drought and it’s the best species we have for stockpiling winter forage. With more knowledge and experience, we can manage this plant to minimize its problems and optimize its benefits.

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  1. my horse pasture was accidentally planted with endophyte infected seed. I immediately turned this seed under and have purchased non-infected pasture grass. My question is what can I do to ensure that the pasture will be safe? What can be applied, I plan on closing off this area of the pasture but want to be certain that what I use to get rid of it will be safe for my horses. Would you recommend an herbicide or another alternative?


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