Herbicide treatments to renovate toxic endophyte infected tall fescue pastures with 'Jesup' MaxQ.

Forage producers need more efficient, less risky, and cost-effective strategies for replacing existing stands of toxic endophyte infected (E+) grass. This study addressed the efficacy of E+ tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort =] control using available herbicides, differing herbicide application timings, and weed control techniques and assessed the survival of E+ seed during the summer after it was produced. Two small-plot experiments near Blairsville and Watkinsville, GA, evaluated herbicide chemistry and compared different application protocols for glyphosate at different time intervals (0, 2, 4, and 6 wk) to the use of a summer annual smother crop between split applications of glyphosate. Glyphosate allowed fewer E+ escapes than the other herbicides tested. Split applications of glyphosate at 6 wk before planting and again 1 d before planting resulted in successful eradication of the E+ tall fescue stand, fewer weeds, and a successfully established stand of nontoxic endophyte infected (NT) tall fescue. In a separate experiment at Blairsville and Watkinsville, 7.4 and 8.5 seeds per 100 seeds produced, respectively, were found to be germinable and with viable endophyte despite exposure to ambient conditions on the canopy floor in 2004. Thus, spring suppression of E+ tall fescue seedheads could reduce the risk of remnant toxic E+ seed. In field-scale tests of the developed protocol [spring suppression of seedheads and a split application of glyphosate (6-wk interval) before an autumn planting], E+ tall fescue stands were destroyed successfully and renovated with a NT tall fescue with a range of E+ escapes being only 0.5 to 2.5%.

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