Using Herbicide Programs to Control Weeds in Corn (Zea mays L.) and Cotton (Gossypium hirsutum L.)

Field studies were conducted to evaluate control of Amaranthus species and other weeds in corn and cotton. In corn, Palmer amaranth control was at least 90% with preemergence applications of fluthiacet‐methyl plus pyroxasulfone, atrazine plus either acetochlor, alachlor, dimethenamid‐P, S‐metolachlor, or S‐metolachlor plus mesotrione, saflufenacil plus dimethenamid‐P, and S‐metolachlor plus mesotrione. When using postemergence herbicides applied to Palmer amaranth less than 5 cm tall, atrazine, prosulfuron, and topramezone alone or the combinations of atrazine plus S‐metolachlor plus glyphosate, diflufenzopyr plus dicamba, dimethenamid plus glyphosate, halosulfuron‐methyl plus dicamba, mesotrione plus S‐metolachlor plus glyphosate, pyroxasulfone plus glyphosate, and thiencarbazone‐methyl plus tembotrione provided at least 91% control. In cotton, pyrithiobac applied preemergence resulted in no greater than 63% of control of Palmer amaranth and common waterhemp at the early season rating. Pendimethalin applied preemergence provided varied levels of control of common waterhemp. Trifluralin, applied preplant incorporated, consistently provided at least 86% or greater control of both species. A decreased level of control of both Palmer amaranth and common waterhemp was observed with pendimethalin applied preemergence followed by pyrithiobac‐applied early postemergence and followed by glufosinate applied mid‐post. Systems which included an early postemergence and mid‐postemergence application of glyphosate plus 2,4‐d choline provided at least 94% season‐long Palmer amaranth control.