Glyphosate-resistant Amaranthus hybridus biotype (smooth pigweed) today covers more than 5 million hectares in crop regions of Argentina. Since it is possible that both glufosinate-, glyphosate- and 2,4-D- tolerant, and glyphosate- and dicamba- tolerant soybean varieties may be available in Argentina, an objective is to determine how effective these technologies are on this weed. To determine the performance of 2,4-D, dicamba and glufosinate thirteen field trials were conducted on A. hybridus in Argentina during 2015, 2016, 2017 and 2018 seasons. 2,4-D choline (456 g a.e./L), dicamba dimethylamine (480 g a.e./L) and glufosinate (280 r a.i/L) were utilized. Post-emergence treatments were applied from 5 to 20 cm in height. Visual % control evaluations were made 4 weeks after application. The 2,4-D choline at 720, 900 and 1140 g a.e./ha provided 73, 80, and 87%, respectively, A. hybridus control that was superior to dicamba at 140, 280, and 560 g a.e./ha providing 36, 52 and 70%, respectively. The addition of glyphosate at 1200 g a.e./ha significantly (66 vs. 80%; p>0.05) improved all 2,4-D and dicamba rates compared to auxinic treatments without glyphosate. Glufosinate alone (500 g ai/ha) showed control 67%. The addition of 2,4-D choline at 900 g a.e./ha to glufosinate significantly (p>0.05) increased control to 90%. Fomesafen at 250 g ae/ha with glyphosate at 1200 g ae/ha provided 55% of control. Utilization of 2,4-D choline and glufosinate+2,4-D choline in glufosinate-, glyphosate- and 2,4-D- tolerant soybean crop programs provide a valuable tools to control glyphosate-resistant A. hybridus biotypes in Argentina.

Key words: smooth pigweed, 2,4-D choline, dicamba, glufosinate, postemergence control.

Presenting Author’s name — R Frene1

Additional Author(s)’s name(s) –; L Lanfranconi, et al2; M Baez Buchanan3, M Ravotti3; L Serafini3, E Teran Vega3

Presenting Author email – rlfrene@dow.com.ar

Corresponding Author email — rlfrene@dow.com.ar

Author 1’s Affiliation – 1Dow-DuPont agricultural division, Buenos Aires, Argentina.

Additional Author(s)’s affiliation – 2Universidad Católica de Córdoba. Cátedra de Protección Vegetal. Et al: L Remondino and J Oliva, ascribed to Universidad Católica de Córdoba. Cátedra de Protección Vegetal. 3Dow-DuPont agricultural division, Buenos Aires, Argentina.

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