Fescue Suppression More Viable Than Eradication

By Donald Stotts

STILLWATER - Endophyte-infected fescue can cause serious health problems in broodmares, but replacing fescue with a more advantageous type of pasture can be a time- and labor-intensive process. "That's why a lot of horse owners settle for removing broodmares from fescue pastures six weeks to three months before the expected foaling date," said Phil Pratt, Oklahoma State University Extension area plant pathologist headquartered at Muskogee.

But while removal may help promote a healthy mare and foal, it also signals a waste of available pasture resources and a potential negative effect on the amount of funds tied up in operational feed costs. "In eastern Oklahoma, fescue is the most persistent, best adapted, cool season perennial forage; unfortunately, most of Oklahoma's fescue is endophyte infected," said Bob Woods, OSU Extension area agronomist. Eradication of existing fescue is difficult, slow and expensive. Thus, suppression of fescue for bermudagrass release may be a more practical option.

Much of the fescue in Oklahoma has invaded existing bermudagrass pastures. Woods said this is partly caused by fescue being well adapted to wet, cool, springtime soil conditions and the typically low pH found in eastern Oklahoma. "Fescue growth is further encouraged by Oklahoma pasture operators' tendency to fertilize before weather conditions are favorable for bermudagrass growth," he said. Woods said herbicides, fertilizer, fire or a combination of these strategies can be used to suppress fescue and recover a stand of bermudagrass.

Recent work in Mayes County successfully changed the dominant grass from fescue to bermudagrass. "Herbicide applications that have demonstrated satisfactory control of tall fescue include Gramoxone applied at 1.5 pints per acre or Roundup applied at two quarts per acre in late March or early April," Woods said. Also, prescribed burning after brownout from an early April herbicide treatment was found to increase the efficacy of the herbicide treatment.

"Fertilizer, especially nitrogen, that is applied before May will tend to favor fescue production at the expense of bermudagrass," Woods said. "Waiting until after May 15 to apply fertilizer will favor bermudagrass production." According to Pratt, laboratory testing has indicated that more than 85 percent of Oklahoma's fescue is infected with the endophytic fungus Acremonium coenophialum (also called Neotyphodium), which is commonly referred to as the fescue endophyte.

"Tests can be conducted to determine infestation rates," Pratt said. "Contact your local Oklahoma Cooperative Extension Service office for test procedures."