Sicklepod (Senna obtusifolia) and Red Morningglory (Ipomoea coccinea) Control in Glyphosate-Resistant Soybean with Narrow Rows and Postemergence Herbicide Mixtures1

Abstract

Field studies were conducted over 2 yr to evaluate weed control, yield, and net returns of glyphosate-resistant soybean using total postemergence (5 wk) (POST) herbicide systems with glyphosate–isopropylamine (Ipa) or glyphosate–trimethylsulfonium (Tms) alone, tank mixed with fomesafen, or in sequential treatments with bentazon, fomesafen, Ipa, or Tms. Soybean early-season injury ranged from 0 to 28% across the test. Although Ipa did not injure soybean, glyphosate–Tms early postemergence (3 wk) (EPOST) injured soybean from 7 to 17% depending on the rate. Glyphosate–Tms mixed with fomesafen EPOST injured soybean from 20 to 28%. Red morningglory control by Ipa and Tms at 0.8 kg ae/ha was no more than 88%. Sequential applications of Tms or Ipa controlled red morningglory 78% or less. Fomesafen improved red morningglory control by Ipa and Tms. Bentazon did not affect the control of red morningglory by these herbicides. Sicklepod, smooth pigweed, and large crabgrass control was 81, 93, and 79%, respectively, o...