Summer Application of Auxinic Herbicides Improves Late-Season Weed Control in Tall Fescue Hayfields
ISSN 2158-9429
Volume 19, Issue 1 - June 2026
Editor: Bindu Poudel-Ward
Furlan Junior, R., Master Student, University of Tennessee
McIntosh, D., Coordinator, University of Tennessee
Fancher, M., Research Assistant, University of Tennessee
Parrish, L., Research Assistant, University of Tennessee
Wright-Smith, H., Assistant Professor, University of Tennessee
Pedreira, B., Associate Professor and Director , University of Tennessee
Abstract
Summer weed pressure in tall fescue (Schedonorus arundinaceus Schreb.) hayfields can limit forage production and reduce nutritive value, especially during summer dormancy. Auxinic herbicides are commonly used for broadleaf weed control in forage systems; however, products with limited soil residual activity may fail to control weeds emerging throughout the summer while tall fescue is dormant. This study evaluated the effects of summer-applied herbicides on weed control, forage mass, and nutritive value at the second hay harvest in a “Kentucky 31” tall fescue hayfield in Greeneville, TN. Treatments included a non-treated control, Grassmaster at 24 oz ac-1 and 32 oz ac-1 (2,4-D + dicamba), Gunslinger at 24 oz ac-1 and 32 oz ac-1 (2,4-D + aminopyralid), and Prescott at 32 oz ac-1 (clopyralid + triclopyr), arranged in a randomized complete block design with four replicates. Visual weed control ratings were assessed at 14, 28, and 84 days after treatment (DAT), and forage and weed mass were quantified at the second hay harvest (84 DAT). Weed control was similar among herbicides through 28 DAT; however, Gunslinger maintained higher control at 84 DAT. All herbicide treatments increased forage mass and reduced weed mass relative to the non-treated control; however, Gunslinger, at both application rates, resulted in the lowest weed mass and the highest forage crude protein concentration. The extended soil residual activity of aminopyralid in Gunslinger contributed to sustained summer weed control during tall fescue’s summer dormancy, improving late-season weed control and hay nutritive value.
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