Weed Control in Corn (Zea maysL.) as Influenced by Preemergence Herbicides

Field studies were conducted in central and south-central Texas from 2013 through 2015 to evaluate crop tolerance and efficacy of various preemergence herbicides alone and in combination for weed control in field corn. Acetochlor and pendimethalin alone,S-metolachlor plus mesotrione, and the three-way combination ofS-metolachlor plus atrazine plus mesotrione provided the most consistent control of annual grasses including browntop panicum (Panicum fasciculatumL.), Texas millet (Urochloa texanaL.), barnyardgrass (Echinochloa crus-galliL.), and sprawling signalgrass (Brachiaria reptansL.). Palmer amaranth [Amaranthus palmeri(S.) Wats.] control was at least 90% with fluthiacet-methyl plus pyroxasulfone, atrazine plus either acetochlor, alachlor, dimethenamid-P,S-metolachlor, orS-metolachlor plus mesotrione, saflufenacil plus dimethenamid-P, andS-metolachlor plus mesotrione. Hophornbeam copperleaf (Acalypha ostryifoliaL.) was difficult to control; however, acetochlor, saflufenacil or pyroxasulfone alone, saflufenacil plus dimethenamid-P, andS-metolachlor plus mesotrione provided at least 90% control. Acetochlor or saflufenacil alone, thiencarbazone-methyl plus isoxaflutole, dimethenamid-P plus atrazine, rimsulfuron plus mesotrione, and saflufenacil plus dimethenamid-P controlled common sunflower (Helianthus annuusL.) at least 90%. Corn injury was minimal (≤3%) with all herbicides. In general, corn grain yield was greatest with herbicide treatments containing more than one active ingredient compared with a single active ingredient.