Efficacy of preemergence application of S-Metolachlor plusFomesafen or Metribuzin as an element in the control of commonwaterhemp (Amaranthus rudis Sauer) in soybeans

摘要

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 ormetribuzin as an element in the control of common waterhemp in soybean. Preemer-gence 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 followedby a postemergence glyphosate application at 0.88 kg ha~(-1). Common waterhemp controlwith S-metolachlor + fomesafen was greater than 88 and 60% at 2 and 8 WAT (WeeksAfter Treatment), respectively at Manhattan in 2005. However, S-metolachlor +fomesafen, regardless of the rate, gave complete common waterhemp control 2 WAT andgreater than 95% common waterhemp control through 8 WAT at Sabetha. In 2005, S-metolachlor + metribuzin controlled 59 and 91% of common waterhemp 8 WAT atManhattan and Sabetha, respectively. By 8 WAT, glyphosate applied after preemergencetreatments improved common waterhemp control; however, no additional control wasachieved with the postemergence glyphosate applications at Manhattan in 2006 andSabetha in 2005. This research showed that early season control of common waterhempcan be achieved with preemergence application of S- metolachlor + fomesafen at 1.52 +0.36 kg ha~(-1) with or without a postemergence application of glyphosate.