Summer Annual Weed Control with 2,4-D and Glyphosate

The introduction of 2,4-D-resistant crops stacked with glyphosate resistance will enable the use of 2,4-D and glyphosate for weed control in corn, cotton, and soybean. Because there is little reported on the effectiveness of 2,4-D plus glyphosate on summer annual weed control, the objective was to evaluate 2,4-D and glyphosate tank mixtures on summer annual weed control. Six rates of 2,4-D (0, 280, 420, 560, 840, and 1,120 g ae ha −1 ) and three rates of glyphosate (0, 840, and 1,120 g ae ha −1 ) were applied to common lambsquarters, common waterhemp, giant ragweed, giant foxtail, and velvetleaf. Glyphosate at 840 g ha −1 controlled all weeds 94 to 100%. Giant ragweed was controlled 99 to 100% by 2,4-D alone when rates were 280 g ha −1 or higher. Common lambsquarters, common waterhemp, and velvetleaf control increased as 2,4-D rates increased, with 1,120 g ha −1 providing 90 to 94% control.