PHOTO: KC Olson, professor of range beef cattle nutrition and management, meets with a group of Flint Hills ranchers to discuss how to effectively manage invasive weed species, especially sericea lespedeza. 

Like many ranchers, Bill Sproul experiences the rewards and challenges of ranching on Kansas’ tallgrass prairie. And he considers sericea lespedeza the No. 1 long-term threat for ranchers in the area. 

Sericea lespedeza is an invasive, noxious weed that infests approximately 600,000 acres of native tallgrass prairie in the Kansas Flint Hills. Tannins in the weed hamper protein digestion by beef cattle and cause abdominal discomfort, so cattle learn to avoid it, which renders some land useless for grazing. 

“It’s a major, major issue. Long term, I feel that it’s the biggest threat to the tallgrass prairie,” said Sproul, who grazes more than 3,000 head of cattle on his Chautauqua County ranch. “The drought is the No. 1 issue short term, but sericea is the No. 1 issue long term.” 

“We’ve been working on it for 10 to 12 years with chemicals, and it’s only gotten worse,” he said. “Chemicals are part of the solution but not the whole solution.” 

K-State Research and Extension scientist KC Olson agrees. He and a team of researchers and extension agents are working with Sproul and others — some of whom are part of an organization called the Tallgrass Legacy Alliance — to find ways to control the weed. 

“One reason for sericea’s invasive nature is its capability to reproduce,” said Olson. “One plant can produce thousands of seeds annually. We address that currently with herbicides. But herbicides are not specific — they kill other valuable plants, plus rugged terrain and the robust tallgrass canopy prevent chemicals from contacting immature plants. Another reason for sericea’s invasive nature is its ability to avoid grazing through its mildly toxic tannins. Without grazing pressure, sericea continues to reproduce unabated.” 

Wildlife biologist Jim Minterath is retired from the U.S. Fish and Wildlife Service but remains involved in the issue. 

“KC’s work stands out because he’s trying to figure out how to live with sericea,” Minterath said. “His approach is probably the only long-term feasible approach. If he succeeds, ecologists will be so thankful.” 

In looking for a safe, inexpensive supplement that could be fed to cattle that might counteract the protein-binding effects of sericea, the researchers identified corn steep liquor (CSL), a nonalcoholic by-product of corn sweetener production, as having strong anti-tannin properties. At the time of the study, CSL sold at about $5 per ton. 

“In a series of five studies, cattle readily consumed it,” said Olson of the supplement, “and suffered none of the digestive disorders characteristic of tannin consumption. Supplementation of 2 to 4 pounds of CSL per day increased acceptance of and tolerance for sericea lespedeza by beef cattle.” 

“That’s significant,” Olson said. “If we can remove the negative consequences of tannin consumption through strategic supplementation, we can probably apply significant grazing pressure to sericea lespedeza and achieve a measure of biological control using the most economically relevant herbivores in the Flint Hills — steers and cows. Benefits may include improved rangeland health, improved animal welfare, reduced herbicide usage, and an inexpensive and manageable control method for this plant.” 

To watch a video about this topic, go to www.ksre.ksu.edu/sericea. 

For More Information:
KC Olson, 785-532-1254, kcolson@ksu.edu 

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