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5 things to know about the fescue endophyte

Craig Roberts for Progressive Forage Published on 12 July 2017

In the May issue of Progressive Forage, an article titled “Summer conversion of toxic tall fescue” was published. The online version of that article prompted follow-up comments from readers. This article will address those comments.

How does the endophyte live in the grass?

Answer: The tall fescue endophyte is a fungus that grows between the cell walls. For most of the year, it is highly concentrated in the crown of the plant. During the spring, as tall fescue enters the reproduction stage, the endophyte grows in the stems and seedheads.

For Kentucky 31 and other popular varieties, the endophyte does not grow in the leaf blade. It grows only in these parts: the crown, the stem and the seedhead.

The endophyte does not reproduce sexually, which means it has no spores. It survives by a vegetative life cycle. After the endophyte infects the seeds, those seeds are pollinated and become fertile. The seed will produce new infected plants with a new generation of infected seeds, which will lead to more infected plants.

This vegetative life cycle affects pasture management. Because the endophyte does not produce spores, it can spread only through the seed.

Can the endophyte die in the seed?

Answer: Yes. The endophyte dies before the seed dies. A bag of seed may have 85 percent live endophyte when it is shipped. But the amount of “living endophyte” can drop to 10 percent. The endophyte will still be there; you can see it under the microscope.

But after one year of storage in a barn, most of it will be dead. Should this seed be planted, it would germinate and the seedlings emerge, but the field will be almost endophyte-free.

It does not take a year to lose “living endophyte” in a bag of seed. The endophyte begins dying within weeks should the bag of seed be left in the hot sun. Because of this, producers should buy new seed, not old seed. Also, producers should buy seed that has been tested and ensured to contain high amounts of living endophyte, then store the seed in a cool, shady place before planting.

Novel endophytes are tested for the amount of living endophyte. The organization that performs the test is the Alliance for Grassland Renewal (, a group of farmers, industry, university, government and non-profit groups.

When the alliance tests reveal the seed contains at least 70 percent living endophyte, they allow a seal to be placed on the bags. That seal is shown in Figure 1.

Alliance for Grassland Renewal

When producers buy a bag of novel endophyte seed, they must look for this seal. It is like a certified seed tag, only for the endophyte. Seed with this seal does not cost more than untested seed.

Can a field of novel endophyte fescue get re-infected with the neighbor’s Kentucky 31 fescue?

Answer: It is possible. But before a new stand can get re-infected, it must first thin. Should the new stand be overgrazed through a severe drought, it would thin and become infested with many weeds. Some of those weeds could be the neighbor’s Kentucky 31 toxic tall fescue.

However, if the new stand remains vigorous, weed infestation is unlikely. Even Kentucky 31 fescue has a difficult time competing in a well-established stand of novel endophyte fescue. In Missouri, we have many fields of novel endophyte fescue that have not re-infected, even though Kentucky 31 is planted in the next field. In fact, re-infection has been rare in our state.

Our stands of novel endophyte have been around well over 10 years.

One way stands of novel endophyte can become re-infected is by feeding Kentucky 31 hay. Where the hay is fed, the existing stand dies. Then new seedlings emerge. Those new seedlings are from the seed of the mature Kentucky 31 hay. For this reason, old Kentucky 31 hay should not be fed on a new stand of novel endophyte.

I hope these comments will help the discussion. If there are other questions, please consider attending a workshop on novel endophytes. These are one-day events that will be held during March 2018 in Missouri, Kentucky and on the East Coast. For more information, keep your eye on the alliance website.  end mark

Craig Roberts is a agronomy professor at the University of Missouri. Email Craig Roberts.