Influence of Diphenylether Herbicide Application Rate and Timing on Common Waterhemp (Amaranthus rudis) Control in Soybean (Glycine max)¹

Abstract

Diphenylether herbicides may be viable options for postemergence (POST) control of common waterhemp in soybean. A 2-yr field research project was conducted to determine whether common waterhemp control is influenced by application timing and rate of acifluorfen, fomesafen, and lactofen. Common waterhemp control was 9, 9, and 8% greater 7, 14, and 21 d after treatment, respectively, after the early postemergence (EPOST) application timing compared with the POST application timing. Lactofen provided greater common waterhemp control than did acifluorfen or fomesafen, and only the highest application of lactofen provided greater than 85% common waterhemp control 21 d after POST application. No significant differences in common waterhemp dry weight were determined among the three rates of acifluorfen, fomesafen, and lactofen applied EPOST. The highest application rates of fomesafen and lactofen reduced common waterhemp dry weight more than did the lowest application rates applied POST. The highest application rate of fomesafen also reduced common waterhemp dry weight more than did the intermediate application rate. Single degree of freedom contrasts indicated that all diphenylether herbicides reduced common waterhemp dry weight more than did imazethapyr.

Control of herbicide-resistant common waterhemp (Amaranthus tuberculatus var. rudis) with pre- and post-emergence herbicides in soybean

“…ha -1 and fomesafen applied at 280 g a.i. ha -1 resulted in 87 and 82% control, respectively, at 21 d after application in a Kansas study (Sweat et al 1998), but only 72 and 77% control, respectively, in an Illinois study when evaluated at equivalent or higher rates (Hager et al 2003).…”

“…Several reports show that sulfentrazone (Sweat et al 1998;Hager et al 2002a) and lactofen (Hager et al 2003) have excellent activity on waterhemp; however, these products are not registered for use in Canada. The PRE herbicides, metolachlor at 1680 g a.i.…”

Control of common waterhemp (Amaranthus tuberculatus var. rudis) in corn and soybean with sequential herbicide applications

“…Acifluorfen and fomesafen have also been shown to provide greater than 90% control of waterhemp (Hager et al 2003;Sweat et al 1998). Shoup and Al-Khatib (2004) reported 90 to 100% waterhemp control with glyphosate.…”

“…(1 provided 87 and 82% control, respectively, at 21 d after application in a Kansas study (Sweat et al 1998), but only 72 and 77% control in an Illinois study, when evaluated at equivalent or higher rates (Hager et al 2003). The pre-emergence herbicides, metolachlor at 1680 g a.i.…”

Comparison of Herbicide Programs for Season-Long Control of Glyphosate-Resistant Common Waterhemp (Amaranthus rudis) in Soybean

“…Relatively lower control of common waterhemp in POST herbicide program can be attributed to the larger plant size at the time of herbicide applications and lower herbicide coverage due to dense population, especially L-POST herbicides that were applied at the plant height of 15-to 20-cm and a density of >100 plants m −2 in the POST-only herbicide programs. Similarly, Hager et al (2003) reported that common waterhemp control was dependent on the height of the plants; therefore, L-POST herbicide applications with acifluorfen, fomesafen, or lactofen showed ≤86% control of common waterhemp, whereas control was up to 91% at 21 DAT with E-POST applications. The PPO-inhibitors are contact herbicides that require adequate spray coverage to provide optimum weed control, especially in dense foliage (Anonymous 2012; Creech et al 2015).…”