Treatment of Tall Fescue pasture with Chaparral© Herbicide in the boot stage of growth reduces tall fescue seedheads

Tall Fescue Toxicosis is a syndrome that impacts the health and well-being of over 10 million beef cows and their calves.  Various strategies have been used to reduce toxin loads, or to improve diet quality to partially mitigate the problem.  In 2018 and 2019, the Amazing Grazing Team conducted demonstrations on eight farms (four/year) to determine if treating Tall Fescue with Chaparral© Herbicide reduce fescue seedheads, and the level of ergot alkaloids.  The project was funded by the NC Cattle Industry Assessment Program. The project took place on working farms throughout the Tall Fescue regions of North Carolina and workshops were held to demonstrate the findings.  On each farm, fields with predominantly Tall Fescue were divided and half was treated with Chaparral© herbicide at a rate of 2 oz/acre.  Application occurred when Tall Fescue was in the boot stage (April 5 – April 30). 

Forage samples were taken in late May following application to determine yield, nutritive value, species and seedhead composition, and ergovaline level in matched side-by-side plots that were judged to be most representative of the treated fields.  Table 1 shows the results.  Tall Fescue seedhead presence was reduced by treatment and this could explain a portion of the reduction in yield.  Treated forages had higher crude protein and Total Digestible Nutrients, which indicates improved nutritive value.  Other studies have shown increase livestock performance with this practice.  Ergovaline is one of the more prevalent compounds that causes Fescue Toxicosis.  The lower levels observed should keep livestock more comfortable and yield higher performance. 

Table 1.  Yield, nutritive value, and ergovaline content of tall fescue pasture after treatment with Chaparral Herbicide. 

Item	Control	Treated	SEM
Dry Matter Yield (lb./acre)	5116a	3172b	422
Tall Fescue Seedhead, %	44.6a	23.6b	4.4
Crude Protein, %	11.2a	13.7b	0.86
TDN, %	56.8a	60.9b	1.05
Ergovaline, ppb	626a	344b	110
Subscripts that differ P<0.05.  SEM is Standard Error of the Mean

With these findings, producers are better equipped to use this practice to mitigate the negative effects of Fescue Toxicosis.  If the forage is destined for hay production then the one ton per acre decrease in  yield is probably not desirable.  In a grazing situation however, the reduction in seedheads and ergovaline, and the increase in forage nutritive value would be desirable and would undoubtedly lead to improved performance.  It would also decrease the need to clip extra seedheads to prevent additional toxicosis during summer.  This might be especially useful on a farm that does not make their own hay.

It is important to note that the outcome was somewhat variable across farms.  One farm didn’t apply until the seedheads had mostly emerged and saw little benefit.  On another farm there was excessive overlap of application which dramatically damaged the tall fescue and total yield.  That farm also did not have much other than tall fescue present, whereas other farms with less yield reduction had other forage species present that could compensate some for the tall fescue damage.

Use of Chaparral© Herbicide to suppress tall fescue seedheads is a tool that can improve forage nutritive value and decrease fescue toxins.  However, it is important to note that seedheads were not completely controlled at any location.  Also, it is important to understand that a yield reduction of about one ton per acre would be expected which would be undesirable in many situations.   Over time, this practice could also reduce the amount of Tall Fescue in fields and favor other grass species.  This can add favorable diversity when the companion grasses are orchardgrass, crabgrass, etc.  Conversely, a weakened Tall Fescue stand can lead to less preferred species like nimblewill, sweet vernal and/or broomstraw.  We strongly recommend determining forage botanical composition and consider the long-term goals for the field before treatment. 

~ Johnny Rogers and Matt Poore, NCSU Amazing Grazing Program

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The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion.  For more resources or to learn more about the Alliance for Grassland Renewal, go to www.grasslandrenewal.org