Control of Palmer Amaranth In GlyTol® + LibertyLink® Cotton

Trials were conducted in Lubbock, TX in 2010 to determine optimum tank-mix and sequential applications of glyphosate and glufosinate in Glytol® + LibertyLink® cotton to control Palmer amaranth.  Tank-mix trials included glyphosate and glufosinate applied at varying tank-mix proportions (1X:0X, 0.75X:0.25X, 0.5X:0.5X, 0.25X:0.75X, and 0X:1X) and varying tank-mix rates (1X:1X, 1X:0.75X, 1X:0.5X, 1X:0.25X and 1X:0X for each herbicide) to two different weed sizes.  Sequential EPOST followed by (fb) MPOST fb LPOST applications of glyphosate or glufosinate applied in all possible timing combinations were also evaluated for effectiveness of control.  Results indicated that tank-mixes of glyphosate and glufosinate were not as effective at controlling Palmer amaranth as either herbicide alone.  Applications made to smaller weeds were more effective than applications made to larger weeds.  Sequential applications, regardless of the sequence, were effective at controlling Palmer amaranth, although treatments with glyphosate as part of the application sequence were more effective than treatments with only glufosinate.