Evaluation of Flumioxazin andS-metolachlor Rate and Timing for Palmer Amaranth (Amaranthus palmeri) Control in Sweetpotato

Abstract

Studies were conducted in 2007 and 2008 to determine the effect of flumioxazin andS-metolachlor on Palmer amaranth control and ‘Beauregard’ and ‘Covington’ sweetpotato. Flumioxazin at 0, 91, or 109 g ai ha−1was applied pretransplant 2 d before transplanting alone or followed by (fb)S-metolachlor at 0, 0.8, 1.1, or 1.3 kg ai ha−1PRE applied immediately after transplanting or 2 wk after transplanting (WAP). Flumioxazin fbS-metolachlor immediately after transplanting provided greater than 90% season-long Palmer amaranth control.S-metolachlor applied alone immediately after transplanting provided 80 to 93% and 92 to 96% control in 2007 and 2008, respectively. Flumioxazin fbS-metolachlor 2 WAP provided greater than 90% control in 2007 but variable control (38 to 79%) in 2008.S-metolachlor applied alone 2 WAP did not provide acceptable Palmer amaranth control. Control was similar for all rates ofS-metolachlor (0.8, 1.1, and 1.3 kg ha−1). In 2008, greater Palmer amaranth control was observed with flumioxazin at 109 g ha−1than with 91 g ha−1. Sweetpotato crop injury due to treatment was minimal (< 3%), and sweetpotato storage root length to width ratio was similar for all treatments in 2007 (2.5 for Beauregard) and 2008 (2.4 and 1.9 for Beauregard and Covington, respectively). Sweetpotato yield was directly related to Palmer amaranth control. Results indicate that flumioxazin pretransplant fbS-metolachlor after transplanting provides an effective herbicide program for control of Palmer amaranth in sweetpotato.