Weed control and crop tolerance of micro-encapsulated acetochlor applied sequentially in glyphosate-resistant soybean

Abstract

. 2015. Weed control and crop tolerance of micro-encapsulated acetochlor applied sequentially in glyphosate-resistant soybean. Can. J. Plant Sci. 95: 973Á981. Acetochlor, an acetamide herbicide, has been used for many years for weed control in several crops, including soybean. Micro-encapsulated acetochlor has been recently registered for preplant (PP), pre-emergence (PRE), and post-emergence (POST) application in soybean in the United States. Information is not available regarding the sequential application of acetochlor for weed control and soybean tolerance. The objectives of this research were to determine the effect of application timing of micro-encapsulated acetochlor applied in tank-mixture with glyphosate in single or sequential applications for weed control in glyphosateresistant soybean, and to determine its impact on soybean injury and yields. Field experiments were conducted at Clay Center, Nebraska, in 2012, and at Waverly, Nebraska, in 2013. Acetochlor tank-mixed with glyphosate applied alone PP, PRE, or tank-mixed with flumioxazin, fomesafen, or sulfentrazone plus chlorimuron provided 99% control of common waterhemp, green foxtail, and velvetleaf at 15 d after planting (DAP); however, control declined to 540% at 100 DAP. Acetochlor tank-mixed with glyphosate applied PRE followed by early POST (V2 to V3 stage of soybean) or late POST (V4 to V5 stage) resulted in ]90% control of common waterhemp and green foxtail, reduced weed density to 52 plants m (2 and biomass to 512 g m , and resulted in soybean yields 3775 kg ha (1 . The sequential applications of glyphosate plus acetochlor applied PP followed by early POST or late POST resulted in equivalent weed control to the best herbicide combinations included in this study and soybean yield equivalent to the weed free control. Injury to soybean was B10% in each of the treatments evaluated. Micro-encapsulated acetochlor can be a good option for soybean growers for controlling grasses and small-seeded broadleaf weeds if applied in a PRE followed by POST herbicide program in tankmixture with herbicides of other modes of action. , avec pour re´sultat un rendement du soja supe´rieur a`3 775 kg par hectare. Les applications se´quentielles de glyphosate et d'ace´tochlor avant les semis, puis au de´but ou a`la fin de la leve´e assurent une lutte e´quivalente aux meilleures combinaisons d'herbicides examine´es dans le cadre de l'e´tude et de´bouchent sur un rendement en soja e´quivalent a`celui de la parcelle te´moin de´sherbe´e. Les traitements e´value´s causent moins de dix pour cent de dommages au soja. Les microcapsules d'ace´tochlor Abbreviations: AMATA, common waterhemp, Amaranthus rudis Sauer; ABUTH, green foxtail, Setaria viridis (L.) P. Beauv; DAP, days after planting; DBP, days before planting; POST, postemergence application; PP, preplant application; PRE, pre-emergence application; SETVI, velvetleaf, Abutilon theophrasti Medik Can. J. Plant Sci. (2015) 95: 973Á981

Overlapping Residual Herbicides for Control of Photosystem (PS) II- and 4-Hydroxyphenylpyruvate Dioxygenase (HPPD)-Inhibitor-Resistant Palmer amaranth (Amaranthus palmeri S. Watson) in Glyphosate-Resistant Maize

“…PRE herbicides, also referred to as soil residual herbicides, are applied to the soil after crop planting but before emergence for controlling germinating or emerging weed seedlings. Soil-residual PRE herbicides generally lose their residual activity in the soil in 30–50 days; however, most POST herbicides commonly applied in maize have minimal to no soil residual activity (Jhala et al, 2015 ; Wiggins et al, 2015 ). Moreover, late-emerging Palmer amaranth plants often escape POST herbicide applications and produce seeds, leading to the replenishment of the soil seedbank and ensuring weed infestations for the next several seasons (Keeley et al, 1987 ).…”

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

“…At 14 DALPOST, POST-only treatments of imazethapyr plus fomesafen plus glyphosate plus acetochlor fb lactofen plus glyphosate reduced common waterhemp density to 30 plants m −2 , which was comparable to several PRE fb POST herbicide programs, including saflufenacil plus imazethapyr, S -metolachlor, or pendimethalin plus metribuzin fb fomesafen plus glyphosate (Table 4). The residual activity of micro-encapsulated acetochlor tank-mixed with other herbicides in POST herbicide programs can suppress common waterhemp emergence later in the growing season (Jhala et al 2015). Similarly, Cahoon et al (2015) and Sarangi et al (2013) reported that micro-encapsulated acetochlor applied alone or tank-mixed with other residual herbicides showed >90% control of common waterhemp and Palmer amaranth, reducing plant density significantly.…”

“…Consequently, glyphosate has become the most commonly used herbicide in agriculture worldwide (Dill et al 2010;Duke and Powles 2008). Moreover, glyphosate-resistant crop technology has encouraged no-till or conservation tillage practices where weed control is primarily based on the application of herbicides (Coffman and Frank 1991;Gianessi 2005;Jhala et al 2014a;Norsworthy et al 2012), which is believed to aid in the shift towards small-seeded broadleaf weed species such as common waterhemp (Culpepper 2006;Legleiter and Bradley 2008;Owen 2008).…”

Evaluation of different herbicides on weed control, yield and yield components of soybean (Glycine max L.)

“…Post-emergence herbicide such as bentazone has been registered for weed control in soybean. A pre-emergence followed by post-emergence herbicide program provided better weed control in soybean compared with solely post-emergence herbicide program in several studies in the United States (Taylor-Lovell et al, 2002;Jhala et al, 2015). (Zarco-Tejada et al, 2000) remark that chlorophyll leaves are one of the most important indicators of environmental stresses on the plant and they believed that the amount of chlorophyll in plants under stress and the total absorption of light by the plant could be reduced.…”