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

Glyphosate- and multiple-resistant waterhemp (Amaranthus tuberculatus var. rudis) in Ontario, Canada

“…Waterhemp is a small seeded, summer annual, broadleaf weed with many traits that make it particularly troublesome in agriculture. Firstly, this weed can emerge in Ontario throughout the entire growing season (Vyn et al 2007), which makes control difficult as most herbicides are applied early in the growing season. Secondly, one female plant in a noncompetitive environment has been documented to produce up to 4.8 million seeds (Hartzler et al 2004).…”

Linuron Biologically Effective Dose for Glyphosate-Resistant Giant Ragweed (<i>Ambrosia trifida</i> L.) Control in Soybean (<i>Glycine max</i> L.)

“…Linuron has also been shown to be effective at controlling 86% and 99% of herbicide-resistant waterhemp (Amaranthus tuberculatus var. rudis) at 10 WAA when applied as early as May 11 and May 29, respectively [28]. Additionally, the primarily wide-spaced soybean rows in this study ( Table 2) may have influenced GR giant ragweed control.…”

“…Linuron plus glyphosate applied PP has been previously reported to give soybean yields of up to 59% [25] and 90% [24] of the weed-free control, when targeting GR giant ragweed. A similar study examined control of herbicide-resistant common waterhemp and found that linuron applied pre-emergence in soybean was sufficient to establish 94% on the weed-free control [28].…”

Control of glyphosate-resistant common waterhemp (Amaranthus tuberculatus var rudis) with dicamba and dimethenamid-P in Ontario

“…It has been documented in Ontario that corn is more competitive with waterhemp than soybean; seed yield loss in soybean in weedy checks was 73% (Vyn et al 2007), compared to 38% in corn (Soltani et al 2009). In a study conducted on waterhemp growth and fecundity in corn, a sharp decrease in biomass and seed production was observed from 80 to 99% when introduced at corn stages V3 to V8 respectively compared to 20% when planted at corn In conclusion, control of GR waterhemp, through the simulated use of the newly approved dicamba-resistant soybean technology provided greater than 95% control of GR waterhemp at 12…”

“…Waterhemp seedlings emerge April to October in Ontario; plants at the cotyledon stage have been observed into late fall (Vyn et al 2007;Schryver et al 2017b). The weed has an erect structure, is a C 4 plant and has been documented with the ability to grow 1.6 mm for every growing degree day (Horak and Loughin 2000).…”