Broadleaf Weed Control in Soybean (Glycine max) with CGA-277476 and Four Postemergence Herbicides1

Abstract

Field research was conducted at three locations in Mississippi to evaluate CGA-277476 tank mixtures with four broadleaf herbicides for possible improvement of broadleaf weed control. Tank mixtures in this research were typically additive, although some instances of antagonism were noted. Control of morningglory (Ipomoea) species and hemp sesbania (Sesbania exaltata) was not consistently improved by the addition of acifluorfen, chlorimuron, fomesafen, or imazaquin to 59 or 79 g ai/ha CGA-277476. However, when a large population of weeds was present, the addition of acifluorfen, chlorimuron, or fomesafen to 59 or 79 g/ha CGA-277476 improved control over CGA-277476 alone. Prickly sida (Sida spinosa) was not controlled more than 68% with any treatment in this study; however, horse purslane (Trianthema portulacastrum) was controlled at least 90% with either 79 g/ha CGA-277476 alone or tank-mixed with acifluorfen, fomesafen, chlorimuron, or imazaquin. The addition of CGA-277476 to acifluorfen or fomesafen did not improve control over acifluorfen or fomesafen alone on any of the weeds evaluated; however, the addition of CGA-277476 to imazaquin improved hemp sesbania control over imazaquin alone. Tank mixtures did not result in yields greater than CGA-277476 alone in areas with moderate weed pressure, whereas in areas with severe weed pressure, tank mixtures improved soybean (Glycine max) yield over CGA-277476 alone.Nomenclature: CGA-277476, 2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl] benzoic acid; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray #3 IPOHG; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A.W. Hill # SEBEX; horse purslane, Trianthema portulacastrum L. # TRTPO; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; soybean, Glycine max (L.) Merr. ‘Hartz 4994’, ‘Pioneer 9592’.Additional index words: Tank mixture, acifluorfen, chlorimuron, fomesafen, imazaquin, IPOHG, IPOLA, SEBEX, SIDSP, TRTPO.Abbreviations: Grn, Greenville; POST, postemergence; Stk-N, Starkville-North; Stk-S, Starkville-South; WAT, weeks after treatment.