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1 December 2017 Sweetpotato Tolerance and Palmer Amaranth Control with Metribuzin and Oryzalin
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Field studies were conducted in Clinton, NC in 2007 and 2009 to determine sweetpotato crop response and Palmer amaranth control with metribuzin and oryzalin. Treatments consisted of 140 and 202 g ai ha-1 metribuzin applied immediately after transplanting [0 wk after transplanting (WAP)] or 2 WAP, 560 and 1121 g ha-1 oryzalin 0 WAP, and tank mixes of metribuzin (140 or 202 g ha-1) and oryzalin (560 or 1,121 g ha-1) 0 WAP. At 2 WAP, metribuzin alone applied 0 WAP resulted in greater crop injury (33%) than oryzalin alone (1%), and the tank mix of metribuzin plus oryzalin resulted in greater crop injury (49%) than either herbicide applied alone. Greater crop injury occurred when metribuzin was applied at 202 g ha-1 (54%) than 140 g ha-1 (34%). Levels of injury were similar at 4 WAP (34, 8, and 52% for metribuzin, oryzalin, and the tank mix, respectively). At 4 WAP, injury from metribuzin was greater when it was applied 0 WAP (34%) compared to 2 WAP (18%). By 10 WAP, injury from metribuzin applied at 2 WAP was only 4%. At 4 WAP, Palmer amaranth control was excellent for all treatments and ≥98%. At 10 WAP, control among treatments ranged from 77% to 85%. Palmer amaranth control provided by metribuzin was similar for applications made 0 WAP (78%) and 2 WAP (77%). Oryzalin alone provided similar control (85%) to metribuzin alone 0 WAP, but greater control than the tank mix (77%). Neither metribuzin nor oryzalin rate differed in weed control provided at 10 WAP. Oryzalin 0 WAP and metribuzin 2 WAP provided no. 1 sweetpotato yields equivalent to the hand-weeded check. No. 1 yields of all other treatments were less than the hand-weeded check but greater than the weedy check.

Nomenclature: Metribuzin; oryzalin; Palmer amaranth, Amaranthus palmeri S. Wats.; sweetpotato, Ipomoea batatas L. Lam. ‘Beauregard’ and ‘Covington’

© Weed Science Society of America, 2017
Stephen L. Meyers, Katherine M. Jennings, and David W. Monks "Sweetpotato Tolerance and Palmer Amaranth Control with Metribuzin and Oryzalin," Weed Technology 31(6), (1 December 2017).
Received: 18 April 2017; Accepted: 1 June 2017; Published: 1 December 2017

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