23 April 2013

5 minute read

North America

Many cow/calf beef enterprises across the state utilize tall fescue as their primary pasture forage. In most instances, it is Kentucky 31 endophyte infected forage, and while this is a great option for a late fall and winter stockpiled forage, there are some significant downsides to using this forage during the growing season, particularly summer.

The endophyte is a fungus, specifically Neotyphodium coenophialum and it is responsible for multiple livestock disorders including fescue foot, bovine fat necrosis and fescue toxicity. Fescue toxicity is the most common disorder and is associated with poor animal performance characterized by reduced feed intake, decreased weight gains, lowered milk production, lowered reproductive performance and rough hair coat.

Last summer's drought may have inadvertently created an opportunity for some beef cattle graziers to reevaluate the tall fescue mix in their pastures. Pastures that were overgrazed during the drought and into the fall period are likely to have "holes" where desirable grass species have dropped out and where weeds may have or will be filling in.

Tall Fescue with Plantain - Last summer's drought kill could be used to used to tired fescue stands with with Sorghum, Sudangrass or Clover, say Mr Lewandowski and Mr Sulc of Ohio State University.

Even those endophyte infected tall fescue pastures could be thinned out; although it is likely the tall fescue will recover and survive. However, these pastures can benefit from renovation.

We are now past the point where frost seeding and broadcasting seed is a viable option. April is a good month to do some no-till drill pasture renovation work. One of the commonly employed strategies to reduce the effects of fescue toxicity is dilution with other species in the pasture.

Endophyte infected tall fescue pastures can benefit from renovation when other species, particularly legumes, are added to the pasture mix.

Generally red and white clover can work well as legume species in a tall fescue stand. The goal should be to establish a 30 to 35 per cent clover mix evenly distributed throughout the fescue pasture. The no-till drill should be adjusted to insure that seed is not placed more than one-quarter to one-half inch deep.

If weeds are present or the tall fescue sod is vigorous then something must be done to reduce this competition and give the new seedlings a chance to establish. The most effective option may be the use of a chemical herbicide.

Always read and follow the label directions regarding rates and possible intervals between application and planting a new crop/seed. Gramoxone can be used as a burndown to provide time for the new seeding to become established. Non-chemical methods include mowing at very short heights or grazing the cover down tight to suppress the grass sod.

There may be situations where eradication of an endophyte infected tall fescue pasture is a better option than renovation and the dilution strategy. Right up front I will say that this is not an easy task and in order for this to be successful it takes a commitment of time and management.

According to some tall fescue management fact sheets from the University of West Virginia and the University of Arkansas, this is a process that will take 1 to 2 years and requires steps to kill the endophyte infected stand, prevent the reintroduction of endophyte infected seed and then continued to management of the new seeding. This process is more likely to have success if there is a pasture field where some tillage machinery can be used.

Although there are variations to this process, if eradication is going to start in the spring, these steps should be followed:

• Soil test to determine if lime, phosphate or potash needs to be added to bring the field to critical soil levels. Those levels are a soil pH of 6.5, a phosphate level of 25 ppm and a potash level of 120 ppm or according to the formula of: 75 +(2.5 x C.E.C.).
• Kill the existing tall fescue sod. Generally glyphosate is the most commonly used herbicide for this purpose. If the sod can't be sprayed until late April or early May, then the pasture must be clipped to prevent any seed head formation.
• If lime or fertilizer is needed to correct soil deficiencies, till the field and incorporate the lime and fertilizer 6-8 inches deep.
• Plant a warm season annual crop such as pearl millet, sorghum x sudangrass or sudangrass when the soil temperature reaches 60 to 65 degrees F. These are vigorous, tall growing forages that will act to smother out any fescue that might germinate. These crops can be used for summer grazing. Another option would be foxtail millet, which would make a single hay crop by late summer (and would not require killing after the single hay crop)
• In late August or early September kill off the summer annual using glyphosate (not necessary if foxtail millet is used). This glyphosate application is another opportunity to kill any surviving tall fescue plants.
• Till the field and prepare a seedbed to plant a winter annual crop such as winter wheat or winter rye. No-till planting is also appropriate. This crop can provide some late fall grazing.
• The next year, depending upon the spring, take a final grazing pass or remove the winter annual as wet wrapped baleage. Take time to walk over the field. If any fescue is observed, apply another application of glyphosate. In mid to late April plant the field with a perennial pasture mix that includes grass and legume species.

After this time period removed from tall fescue seed head production, any tall fescue that emerges from old seed in the soil should no longer contain a viable infective fungus. A fact sheet on endophyte toxins from Oregon State University says that the fungus will lose its viability if stored for 18 or more months. Other sources say 12 months is enough for the fungus to lose its viability in stored seed.

Finally, even if eradication is successful, the grazier must continue to manage to prevent endophyte infected seed from being re-introduced into the field from machinery and/or animals carrying viable seed in their digestive tracts from endophyte infected fields. Infected tall fescue can also be reintroduced by feeding hay of endophyte-infected tall fescue containing seed heads with viable seed.

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