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

Abstract

Soltani, N., Vyn, J. D. and Sikkema, P. H. 2009. Control of common waterhemp (Amaranthus tuberculatus var. rudis) in corn and soybean with sequential herbicide applications. Can. J. Plant Sci. 89: 127Á132. Common waterhemp (Amaranthus tuberculatus) is an aggressive annual broadleaf whose distribution is expected to increase rapidly in agricultural land in eastern Canada. Eight field experiments (four in corn and four in soybean) over a 2-yr period (2005 and 2006) were established on two Ontario farms (near Comber and Petrolia, Ontario) with waterhemp infestations to evaluate the efficacy of various PRE-and POST-emergence herbicides applied alone or in sequence for the control of waterhemp in corn and soybean. There was minimal injury (up to 3.8%) to corn and soybean from the herbicide treatments evaluated. In corn, sequential herbicide programs of isoxaflutole'atrazine PRE fb either dicamba POST, dicamba/diflufenzopyr POST, dicamba/atrazine POST or mesotrione'atrazine POST provided consistent full-season control of waterhemp. Corn yield was reduced 48% when waterhemp was not controlled. Corn yield was equivalent to the weed-free check with the herbicide treatments evaluated. In soybean, PRE or POST herbicides alone provided 41 to 94% control of waterhemp, however, waterhemp control was increased to 90 to 99% with the sequential herbicide programs. Dimethenamid (PRE; 1250 g ha ) followed by glyphosate (POST2; 900 g ha (1 ) controlled waterhemp 99%. Results with waterhemp density and biomass were similar to visible control. Soybean yield was reduced 41% when waterhemp was not controlled. Soybean yield was equivalent to the weed-free check with all the herbicide treatment except dimethenamid PRE, acifluorfen POST1 and fomesafen POST1 where the yield was 30, 19, and 19% lower, respectively.

Control of Photosystem II– and 4-Hydroxyphenylpyruvate Dioxygenase Inhibitor–Resistant Palmer Amaranth (Amaranthus palmeri) in Conventional Corn

“…Ganie et al (2017) observed 2% to 4% corn injury at 7 DAPRE with saflufenacil plus dimethenamid-P at a rate higher (780 g ha −1 ) than that applied in this study (390 g ha −1 ). Some studies also reported minimal to no corn injury with dicamba (600 g ha −1 ), dicamba plus diflufenzopyr (200 g ha −1 ), or dicamba plus halosulfuron (380 g ha −1 ) at 14 DAPOST (Ganie et al 2017; Kohrt and Sprague 2017; Soltani et al 2008). VanGessel et al (2016) reported hybrid corn stunting and leaf chlorosis up to 10% at 7 DAPOST application of dicamba plus diflufenzopyr at twice (588 g ha −1 ) the labeled rate.…”

Biologically-Effective-Dose of Tolpyralate and Tolpyralate plus Atrazine for Control of Multiple-Herbicide-Resistant Waterhemp [<i>Amaranthus tuberculatus</i> (Moq.) J. D. Sauer] in Corn

“…When left uncontrolled, waterhemp can reduce corn yield up to 74% [18]. In Ontario, corn yield loss up to 48% has been reported [19]. Corn should be kept weed-free from emergence (VE) to the V6 corn stage to prevent yield loss caused by waterhemp interference [18].…”

Is There a Benefit of Adding Atrazine to HPPD-Inhibiting Herbicides for Control of Multiple-Herbicide-Resistant, Including Group 5-Resistant, Waterhemp in Corn?

“…Waterhemp left uncontrolled can reduce grain corn yield by up to 74% (Steckel & Sprague, 2004). In Ontario, corn yield losses of up to 48% have been reported when MHR waterhemp population resistant to Group 2 and 5 herbicides were left uncontrolled (Soltani et al, 2009). HPPD-inhibiting herbicides are widely used in corn production due to their crop safety, flexible application timing, broad spectrum weed control and activity on many HR weed species.…”