Agricultural/Livestock Information


Tall Fescue Toxin Concentrations in Hay and Silage

Kentuky-31 tall fescue, the most used grass in Missouri pastures, contain an endophyte fungus that produces toxic alkaloids.  The toxic ergot alkaloids can lead to a condition called fescue toxicosis.  Fescue toxicosis is a severe forage-livestock disorder costing Missouri’s beef industry $160 million each year in reduced weaning weights, conception rates, and milk production. 

Many farmers wonder what happens to tall fescue toxin levels when it is baled for hay.  Toxin levels decrease in hay.  This is because ergot alkaloids break down in the presence of light, heat, and oxygen.  About one half of the toxins disappear within six months after baling.  Even though the toxin levels are reduced the forage is likely above threshold levels for fescue toxicosis and other alkaloid management strategies will need to be implemented.  Full article:  Roberts et al., 2009. Crop Sci. 49:1496-1502.

Producers should use caution when feeding toxic, tall fescue silage.  When silage is made (oxygen is deprived) the toxins remain and are well preserved.  Full article:  Roberts et al., 2014. Crop Sci. 54:1887-1892.

Wet weather conditions this spring have delayed hay and silage harvest for a large portion of Missouri.  The delay in harvest has resulted in tall fescue seedheads emerging in hayfields.  When tall fescue is reproductive, the seedhead is one of the most toxic portions of the plant.  Hay and silage containing seedheads should be considered highly toxic.

Whether tall fescue is manage for pasture, hay, or silage there are some strategies that should be implemented to minimize the impact to livestock.  Producers should strive to manage tall fescue to minimize toxicity by incremental alleviation, which is the additive effect of several management practices.  Incremental alleviation includes interseeding legumes and other forages, rotating livestock to warm season grass paddocks, nitrogen management, and grazing height management.

Incremental alleviation does not directly address the production of toxic alkaloids in tall fescue.  Replacing tall fescue with novel endophyte fescue is the only way to completely eliminate the costly effects of fescue toxicosis.  Fields converted to novel endophyte tall fescue should follow the spray-smother-spray protocol prior to establishment.  Novel endophyte tall fescue cultivars will have the Alliance for Grassland Renewal label which verifies that it meets novel specification.

Contact Sarah Kenyon, Field Specialist in Agronomy, for more information or 417-256-2391.  Also, the guide sheet Tall Fescue Toxicosis can give more information on this complex issue:

South Central Missouri AG News:

Dr. Sarah Kenyon, Field Specialist in Agronomy  and Elizabeth Picking, Field Specialist in livestock along with Ted Probert, Wright County Dairy Specialist and  Eric Meusch , Agriculture Educator, Texas County publish a quarterly  online newsletter.  If there is a topic that you would like information on contact, Elizabeth Picking at   
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May 8, 2019
True Armyworms Have Been Found in the Region

True armyworms have been found in grass pastures in south central Missouri.  Farmers should begin scouting pastures, wheat, and corn fields. 

Dusk or dawn is the best time to scout for the insect, because the young larvae feed at night.  During the heat of the day they will hide under plant debris on the ground. 

True armyworm larvae are identified by having an orange stripe along each side of the body and a dark spot or triangle on each of the abdominal prolegs located in the center of the body.  The head is brown with honeycomb markings.  See figure 1.  

True armyworm typically feed on grass species; therefore, pastures, wheat, and corn crops are at highest risk.  In pastures and wheat crops treatment is justified when four or more nonparasitized, half-grown or larger larvae are present per square foot.  The insect will not only defoliate the plant, but they can clip seed heads as well; for seed crops treatment is justified when 2-3% of the heads have been cut.  For corn crops the economic threshold is when 10% or more of the plants are injured and larvae are less than ¾ inch.

If threshold levels are observed farmers should treat the impacted field quickly.  Insecticides can be used, or the forage can be harvested by haying or grazing.

Natural parasites can impact some true armyworm populations; although, none have been observed in fields scouted to date.  Armyworms that have been affected will be dark in color and will be mummified on the plant stalk.  The larvae will typically be positioned with the head pointed downward.  See figure 2.

Scouting should continue to verify the presence or absence of the parasites.  Also, true armyworm moths could migrate in and re-infest an area.  Farmers can find more information in the MU Extension guide "Management of the Armyworm Complex in Missouri Field Crops" at

MU Extension agronomist Sarah Kenyon says, “Very high numbers have been observed in portions of Christian, Howell, and Ozark Counties.  Farmers should be scouting fields and be prepared to take action."

For more information, or with further questions please contact your local Extension office.

Figure 1.  True armyworm can be identified by the orange stripe that run longitudinally down the body and dark triangular spots on the prolegs.  Photo courtesy of G. Luce. 

Figure 2.  Mummified true armyworm on a grass stalk.  Photo courtesy of J. Kenyon.

This video is for wheat, but scouting grass hayfields and pastures would be similar.

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