Evaluation of S-Metolachlor and S-Metolachlor Plus Atrazine Mixtures with Mesotrione for Broadleaf Weed Control in Corn

Abstract

Field experiments were conducted in 2001, 2002, and 2003 to evaluate PRE applications of mesotrione at 150, 230, and 310 g ai/ha alone, and in mixtures with S-metolachlor at 1,070 g ai/ha and atrazine at 560 and 1,120 g ai/ha in corn. Corn injury was 11 to 18% with all treatments in 2002 when 3.2 cm of rainfall occurred within 10 d after PRE applications, but no injury was observed in 2001 and 2003 when rainfall was 0 and 1.1 cm within 10 d after PRE applications, respectively. Rainfall following PRE herbicide applications also influenced weed control, where weed control was generally poor with all herbicide treatments in 2001. Mesotrione at 150 g/ha controlled common lambsquarters and smooth pigweed at least 95% in 2002 and 2003, but control was 70% or less in 2001. PRE mesotrione at rates of 230 or 310 g/ha controlled common ragweed at least 83% in 2002 and 2003, but control exceeded 88% with mixtures of mesotrione at rates greater than 150 g/ha plus S-metolachlor plus atrazine at 560 g/ha. Morningglory species (ivyleaf morningglory, pitted morningglory, and tall morningglory) were not consistently controlled by mesotrione alone. In 2002 and 2003, mixtures of all mesotrione rates plus S-metolachlor plus atrazine at 1,120 g/ha controlled morningglory species at least 90%. Corn treated with mesotrione at any rate plus S-metolachlor plus atrazine at 1,120 g/ha consistently produced high yields. It is concluded that control with this three-way mixture would be most consistent with a minimum rate of mesotrione at 230 g/ha and atrazine at 1,120 g/ha.