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Off with their heads: The pros and cons of fescue seedhead suppression

Dennis Hancock for Progressive Forage Published on 21 February 2017
seedheadless fescue vs. fescue with seedheads

“Off with their heads!” is the trademark phrase of the Queen of Hearts, a vile and loathsome character in Lewis Carroll’s Alice in Wonderland. Whenever she was even slightly annoyed by one of her subjects, she would command this terrible fate for them. This is obviously not a good character trait, unless one applies the “off with their heads” philosophy to tall fescue. As it turns out, headless tall fescue is greatly beneficial to animal performance.

Since the release of Kentucky 31 tall fescue in 1943, it has been planted on nearly 40 million acres of pasture and hay fields. It is high yielding and holds a good stand even under some really abusive management. But, over 90 percent of the tall fescue in this country has a fungus that grows inside it called Epicloë coenophialia. This fungus is a partner with the tall fescue. It helps the fescue fight off hard times, like when it gets hit by insects, disease, drought stress and overgrazing. Even though this partnership makes it resilient, it also causes fescue to produce certain types of plant compounds that are toxic to animals.

Compared with nontoxic fescue, cows grazing toxic tall fescue give around 25 percent less milk, spend about 20 percent less time grazing, drink 25 percent more water and lose up to 2 points of body condition. Their calves have weaning weights that are 60 to 90 pounds lighter and gain about 40 percent less. When looking at 23 research studies from across the fescue belt, researchers found that cow herds grazing toxic tall fescue had pregnancy rates averaging about 60 percent. Cattlemen who fail to produce a calf crop from at least 90 percent of their cows are failing to optimize their production. So, for a lot of cattlemen, toxic tall fescue is stealing them blind.

It is known that the toxin load is as much as 10 times higher in the seedheads of tall fescue than it is in the leaf blade. So, what if one took the Queen of Hearts’ approach and declared “Off with their heads!” in a pasture infested with toxic tall fescue?

It is known that certain herbicides can prevent seedhead formation in tall fescue. Some researchers in Kentucky and Missouri sought to determine what impact these herbicides could have on forage quality, animal performance and reproductive efficiency. In the Kentucky study, pastures were treated with Chaparral from Dow AgroSciences, the only product on the market that is currently labeled for tall fescue seedhead suppression. Treated pastures had more than 90 percent fewer seedheads, 42 percent higher crude protein, 14 percent more water soluble carbohydrates and 13 percent more digestible forage than untreated pastures. They used stocker calves to measure the effect on animal performance, and they found average daily gains increased nearly 40 percent when the seedheads were chemically suppressed.

In 2014, researchers at Missouri State University worked with Circle A Angus in Stockton, Missouri, to collect data on 12 of their herds, each on different toxic tall fescue-based farms. Circle A supplements their cows each day with dried distillers grains to ensure nutrition isn’t holding back reproductive efficiency. For this trial, they treated eight farms with the seedhead suppressing herbicide, and four of their units had no herbicide treatment. The farms that were treated averaged an 89 percent pregnancy rate, while the untreated farms averaged 80 percent.

So what’s the catch? Seedhead suppression in tall fescue does come at a cost. The first challenge is that treated fescue will look yellow and stunted for a few weeks after the application. Even at the low rates recommended for seedhead suppression, the metsulfuron in Chaparral will stunt the fescue. In addition to the yellowing, it reduces the yield of tall fescue, mainly because it reduces seedhead production by over 90 percent. This shouldn’t be surprising, since seedheads often account for more than half of the total forage produced by tall fescue in the spring.

Unfortunately, this yield reduction results in fewer animals per acre. This short-term reduction in stocking density is overwhelmed by increased weaning weights and reproductive efficiency, such that the pounds of weaned calves produced per acre is substantially improved by the application of Chaparral for seedhead suppression. Though a detailed economic evaluation has not been done, the increased calf crop from treated fields appears to be profitable in most years. And, if the field needed to be treated with a broadleaf herbicide anyway, it appears to be a win-win.

To date, there’s been limited research on the effects of long-term use of seedhead suppression and whether or not it will shorten stand life. It is recommended that no more than half of one’s acreage be sprayed each year and that the pastures be rotationally grazed to minimize stress. With these precautions, the risks are low and the benefits are high.

If you are interested in using Chaparral for seedhead suppression, use these steps for best results:

  1. Ensure that the tall fescue stand is strong, fertilized according to extension recommendations, and treat no more than 50 percent of your acreage in a given year.
  2. Apply Chaparral at a rate of 2 ounces per acre in spring, sometime between three weeks prior to reproductive tiller development and just before the seedhead emerges (boot stage).
  3. The fescue will be stunted for a few weeks, so adjust stocking density to ensure adequate pasture is provided to livestock on treated pastures during the short-term yield difference.
  4. For best results, use rotational grazing to minimize the risks of overgrazing and maximize stocking rates.  end mark

Note: Mention of an individual product or company name does not imply endorsement. The product recommended in this article is currently the only product labeled for the practices recommended herein.

Dennis Hancock
  • Dennis Hancock

  • Forage Extension Specialist
  • University of Georgia
  • Email Dennis Hancock

PHOTO: Tall fescue seedhead suppression using Chaparral (left) compared to the untreated control (right) a few weeks after application. Photo provided by Dr. Ben Goff with the University of Kentucky.