February 28, 2017
Toxic tall fescue resists herbicide
but smothers under a cover crop
COLUMBIA, Mo. - Killing old stands of tall fescue pastures takes an all-out assault. Kentucky 31, the toxic tall fescue, doesn't die easy.
The K-31 has a good feature. It's hardy. That lets it withstand hazards from pests to droughts to overgrazing.
Herd owners like that. However, K-31's strength comes from a toxin that causes losses in grazing herds.
Craig Roberts, University of Missouri Extension forage specialist, has led efforts to renovate pastures for years.
Financial rewards drive planting new novel-endophyte fescues. Toxic fescue costs Missouri cow herd owners an estimated $190 million a year. Toxins cause lost gains, low conceptions, poor milk and lost cattle.
It took a long time to solve the problem, which comes from a fungus, or endophyte, that grows between plant cells in the grass, Roberts says. The fungus earns its keep protecting the host. Ergovaline, the toxin, helps the plant survive.
Getting rid of the toxin means replacing the toxic variety with an endophyte that is nontoxic.
Total eradication is needed before planting new novel-endophyte varieties.
But toxic fescue doesn't die with one spraying of herbicide. Eradication must kill standing grass, surviving tillers and seed left in the soil.
Years ago, MU Extension specialists found a system that works. A series of workshops in March will teach the spray-smother-spray method. The one-day classes will be held in Kansas, Missouri and Kentucky.
The method takes time-at least one growing season. Typically, the pasture is sprayed with an herbicide in spring. Then a cover crop, such as pearl millet, is drilled into the dying sod. The crop provides grazing, but also smothers grass seedlings that sprout from seed in the soil. Finally, a second spraying in the fall kills the cover crop. That also takes out tough tillers and seedlings that survived smothering.
"Almost everyone thinks of a way to shorten the process," Roberts says. "Shortcuts don't work. The eradication recipe is time-tested. It should be followed."
The specialists warn that endophyte-free fescues don't work. They die out the first year.
The Alliance for Grassland Renewal conducts the workshops. The Alliance, started in Missouri, is made up of participants in pasture production. That includes industry leaders, farmers and university specialists.
The Alliance cooperates with extension services in Missouri, Kansas and Kentucky.
School dates and locations:
- March 6, Mound Valley, Kan., Community Center.
- March 7, Mount Vernon, Mo., MU Southwest Center.
- March 9, Lexington, Ky., UK Veterinary Diagnostic Lab.
Each school runs 9 a.m. to 5 p.m.
With limited seating, advance registration is required at all schools. Registration details are at grasslandrenewal.org.
Source: Craig Roberts, 573-882-0481