Field and greenhouse studies were conducted in 2000 and 2001 in Mississippi to determine the most effective POST herbicide programs for control of Texasweed in glyphosate-resistant soybean. In the field, Texasweed plants recovered from most POST herbicide treatments, and plant death rarely occurred. A sequential application of 1,100 g ae/ha glyphosate followed by 840 g/ha glyphosate was the only treatment that controlled at least 90% of Texasweed 4 wk after treatment. Texasweed control ranged from 80 to 87% for lower rates of glyphosate applied once or twice and 390 g ai/ha fomesafen. The addition of fomesafen or other herbicides to glyphosate did not improve control compared with glyphosate alone. In the greenhouse, glyphosate at 560 g/ha controlled 93 and 90% of one- and two-leaf plants, respectively, but at least 1,400 g/ha was required to obtain 90% control of four-leaf plants. Fomesafen at 260 g/ha controlled 93 to 99% of one- to four-leaf Texasweed plants in the greenhouse.
Nomenclature: Fomesafen, glyphosate, Texasweed, Caperonia palustris (L.) St. Hil, soybean, Glycine max (L.) Merr