One of the most effective ways to eliminate endophyte-infected tall fescue is a fall application of glyphosate or products of similar activity. Early to mid-October prior to a killing frost is the ideal time to apply RoundupTM at a rate of two quarts in 20-30 gallons of water per acre. Addition of 17 lbs. of a spray-grade ammonium sulfate per 100 gallons of spray will enhance uptake of RoundupTM and effectiveness of control. An early-spring seeding can then be made into the killed sod with whatever forages are desired. The fall-killing fescue program allows for more complete control than spring-applied herbicide and little potential for soil loss over winter and during the seeding process. Alternately, fescue can be killed in the spring with RoundupTM or by planting a summer-annual smother-crop like sorghum sudangrass, and in September by planting a cool-season grass.
New endophyte-free varieties or varieties with very low endophyte levels are now available. Farmers making new seedings of tall fescue to be used for animal feed should select one of these new varieties. Endophyte-free tall fescue is more persistent than orchardgrass and bromegrass, yet can be less tolerant of plant-stress than a stand of infected Kentucky 31 fescue. Endophyte-infected fescue is more resistant to insects and diseases, is more drought-tolerant and actually grows better and is more productive than endophyte-free plants. Grazing livestock prefer fungus-free fescue over infected fescue. Endophyte-free fescue may require substantially different management than endophyte-infected fescue due to a greater susceptibility to overgrazing and a less-hardy nature. New fescue-clover stands should be watched closely and, if the fescue is being shaded, just enough grazing pressure should be applied to avoid a problem. Most cool-season grasses are slow to establish, particularly with aggressive legumes like red clover.
Reinfection is possible. A complete kill of the infected fescue stand is required or some level of infection will be detected in the future. Wind is not likely to move infected seeds to endophyte-free fields. In addition, birds do not seem to move the seed nor would wild animals be expected to move significant numbers of seeds. However, cattle can move substantial numbers of seeds and thus infect endophyte-free fescue fields. About two percent of the infected seed ingested by a cow can germinate and result in the establishment of infected plants. Rotational grazing between infected and non-infected pasture can aggravate the problem if mature seeds are present in the pastures.
Reseeding With Other Cool-Season Grasses
Another option involving pasture renovation would be to establish a stand of another cool-season grass species like orchardgrass in place of endophyte-infected tall fescue. This would certainly improve animal performance, but producers need to be aware most other cool-season grasses will not tolerate the heavy use and abuse like infected tall fescue. Forage management will be more critical to ensure stand persistence in this case.
Avoid grazing infected fescue when seed heads are present, as the toxic factors tend to increase with plant maturity. This involves keeping the forage in a vegetative state as long as possible by grazing or clipping. Grazing fescue pastures in the spring, moving cattle to other grass pastures and clipping fescue during the summer and then grazing the tall fescue regrowth again in the fall appears to reduce toxic effects of the endophyte. Fescue hay should be cut early, and should not be the only nutrient source fed to cattle in the winter if hay fields are heavily endophyte-infected.
An option that can be successfully used to reduce the toxic effects of endophyte-infected tall fescue without the expenses of pasture renovation is to dilute the endophyte. This can be done several ways. Supplementation of cattle consuming tall fescue with grain will dilute the endophyte; however, feeding high levels of grain (greater than 4-6 lbs.) to cattle eating primarily a forage-based diet will decrease forage intake and digestibility.
Including legumes in a fescue pasture can reduce or eliminate the fescue toxicity. Legume choices include red clover, ladinoclover, birdsfoot trefoil and alfalfa. Since tall fescue stands are usually very thick, it can be difficult to get legumes to persist in an established stand. Controlling height of fescue to allow light down to the legumes, proper pH and phosphorus levels will be critical to maintaining legumes.
Red clover is probably one of the best choices of legumes to interseed into fescue pastures because of its hardiness and ability to compete with the grass. This can be easily accomplished by mixing red clover seed with fertilizer and broadcasting the mixture in early spring. Mixing with fertilizer may actually help germination of red clover because of the abrasive action of the hard seed coat. Red clover is a biennial legume and may need to be reseeded every year to every other year, depending on forage management.
Ladinoclover or white clover, is a perennial legume used in combination with tall fescue. It grows close to the ground and, therefore, will tolerate close grazing, but is not a good choice for hay production. Ladinoclover is not as competitive with fescue as red clover, but it will produce a lot of seed to keep the legume stand persistent when hot, dry summers can kill the mature plants. White clover spreads by stolons as well as seed. In most areas, white clover will just appear as grazing management improves.
Birdsfoot trefoil is a long-lived perennial legume, but it is not very competitive compared with red clover. It will persist in mixed stands if pastures are mown when grass competition is the greatest. It can be grazed frequently, but will not tolerate too close grazing, as about four inches of leaf material needs to be left for the stand to persist.
Alfalfa can be used in fescue mixtures, but high levels of forage management are necessary for it to persist. Alfalfa is very sensitive to frequent grazing, but it can be grazed closely and it is an excellent choice for hay production.
Management Practices That Help When Interseeding Legumes in a Tall Fescue Pasture
1. Graze the pasture heavily in the fall or winter prior to establishment to help control grass competition and expose soil to enhance seed to soil contact and provide sunlight for germination.
2. Apply higher levels of potassium and phosphate in spring and do not apply nitrogen.
3. Apply adequate lime since most legumes are more sensitive to acid pH and require more calcium than grasses.
4. Graze frequently to reduce grass competition and provide light to the legume seedlings.