Efficacy of preemergence application ofS-Metolachlor plus Fomesafen or Metribuzin as an element in the control of common waterhemp (Amaranthus rudis Sauer) in soybeans

Abstract

Abstract Field experiments were conducted near Manhattan, KS in 2005 and 2006 and Sabetha, KS in 2005 to determine the efficacy of S-metolachlor tank-mixed with fomesafen or metribuzin as an element in the control of common waterhemp in soybean. Preemergence treatments included S-metolachlor + fomesafen at 0.91 + 0.22, 1.21 + 0.28, 1.52 + 0.36, and 1.82 + 0.43 kg ai ha−1 (kg active ingredients per hectare) and S-metolachlor + metribuzin at 2.42 + 0.59 kg ai ha−1. These treatments were applied alone or followed by a postemergence glyphosate application at 0.88 kg ha−1. Common waterhemp control with S-metolachlor + fomesafen was greater than 88 and 60% at 2 and 8 WAT (Weeks After Treatment), respectively at Manhattan in 2005. However, S-metolachlor + fomesafen, regardless of the rate, gave complete common waterhemp control 2 WAT and greater than 95% common waterhemp control through 8 WAT at Sabetha. In 2005, S-metolachlor + metribuzin controlled 59 and 91% of common waterhemp 8 WAT at Manhattan and Sabetha,...