April 30, 2017 01:22 PM

As we discussed in the March 2017 column, renovating a toxic fescue pasture to beneficial endophyte varieties is no small feat. To ensure success, retired University of Kentucky weed scientist Bill Witt said producers should take a long-term, proactive approach. The length of renovation period chosen will depend on each operation’s specific circumstances, he noted, but should range between one and two years.

Witt suggested the following possible lines of attack to combat toxic fescue and promote establishment of new seedings.

Strategy 1 (one year)

  • Spring burndown of toxic fescue with glyphosate
  • Plant a cover or smother crop (for example, sorghum-sudangrass)
  • Second burndown in late summer
  • Plant beneficial endophyte fescue in early fall

Strategy 2 (up to two years)

Year 1:

  • Spring burndown of toxic fescue with glyphosate
  • Plant corn for silage or cover/smother crop
  • After harvest, till soil and/or spray weeds (if necessary) and then plant a small grain

Year 2:

  • Harvest small grain early for hay or silage in spring
  • Apply one to two burndown treatments with glyphosate in late summer (dependent on weeds)
  • Plant beneficial endophyte in
  • early fall

Of both long-term choices, Witt pointed out, the second strategy is the most effective at reducing toxic seed numbers in the seed bank. This length of time gives producers two full seasons for any remaining seeds to germinate. Planting in early fall, specifically September, he explained, is the best time frame to reseed pastures in the upper transition zone as competition from weedy annual grasses is least prevalent.

In his experience, Witt described that ultimately the biggest reason new seedings fail is usually related to postplanting practices, such as weed infestation or grazing plants too soon. Hold off on grazing newly planted pastures until grass seedlings are well established, Witt said.

“If you can grab hold of some plants with three to four tillers and they don’t pull out of the ground, then I call that established,” Witt said.

A similar rule of thumb applies to spraying new seedings for weeds. Most herbicides list a statement on their label emphasizing, “Do not apply to newly seeded areas until grass becomes well established.” Spraying too early can damage young seedlings and potentially set a stand back.

Rather than spray, USDA-Agricultural Research Service scientist Glen Aiken recommended mowing pastures in the first year as a means to control weeds. This action will also help to prevent seedhead formation and reduce the risk of any rogue toxic fescue plants from producing seed.

In Year 2, Aiken said, graziers might consider spraying beneficial endophyte pastures with Chaparral (Dow Agrosciences). The herbicide has been shown to successfully suppress seedhead formation in tall fescue plants.

“In a pasture setting, toxic fescue seeds have been shown to survive upward of two years,” says Aiken. “So, that initial time period is critical for controlling seedheads.”

Aiken noted that while this goes against most graziers’ desire to let new plants reseed, it’s important to keep toxic fescue at bay for the first couple years after establishment.

Along with these postplanting steps, Witt and Aiken leave producers with the following proactive tips to ward off toxic fescue in pastures as novel endophyte stands mature:

Rotate pastures: Because cattle are free from the negative effects of toxic fescue when grazing novel endophyte pastures, they spend more time grazing than their counterparts grazing Kentucky 31. “Since they’re grazing more, intakes are going to be higher,” Aiken said. “Because of this you have to be more aware of your stocking rates and use rotational grazing methods.”

Aiken suggested leaving about 4 inches of plant residue when rotating pastures.

Keep equipment tidy: One of the most common ways weedy plants become introduced to pastures is via dirty equipment, such as a mower. Keep equipment clean to help prevent hitchhiker seeds from making their way into beneficial endophyte pastures.

Beware of toxic fescue hay: Sometimes producers must buy off-farm hay to feed livestock. To prevent transfer of any toxic fescue seeds that might be harbored in off-farm hay to novel endophyte fescue pastures, feed livestock in a controlled sacrifice lot.

Use holding areas: Cattle are most likely to ingest large amounts of seedheads late in the grazing season. During this time of year, it’s best to hold cattle in a sacrifice area for three or four days before moving animals onto beneficial endophyte pastures. This will allow adequate time for any ingested toxic fescue seeds to pass through the animal’s digestive tract.

This article appeared in the April/May 2017 issue of Hay & Forage Grower on page 11.

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