Triazine-Resistant Common Lambsquarters (Chenopodium album) Control in Corn with Preemergence Herbicides1

Triazine-resistant common lambsquarters (TR-CHEAL) is a widespread weed problem in the northcentral United States. Field studies were conducted from 1995 to 1997 to determine the efficacy and consistency of metolachlor, pendimethalin, and acetochlor applied preemergence (PRE) for control of TR-CHEAL in corn. Pendimethalin provided greater (98%) and more consistent control of TR-CHEAL than metolachlor (66%) or acetochlor (86%). Studies were conducted from 1998 to 2000 to examine the potential of isoxaflutole, flumetsulam, and rimsulfuron plus thifensulfuron for control of TR-CHEAL in corn. In 1999 and 2000, isoxaflutole (35 g ai/ha), flumetsulam (35 g ai/ ha), and rimsulfuron plus thifensulfuron (26 g ai/ha) provided 98% or greater control of TR-CHEAL. In 1998 when rainfall was limited after application, isoxaflutole (70 g ai/ha) and flumetsulam (70 g ai/ha) provided 65 and 55% control, respectively, and rimsulfuron plus thifensulfuron (26 g ai/ha) provided 55% control. Results indicate that control of TR-CHEAL with currently labeled PRE herbicides is possible. Nomenclature: Acetochlor; flumetsulam; isoxaflutole; metolachlor; pendimethalin; rimsulfuron; thifensulfuron; triazine; common lambsquarters, Chenopodium album L. #3 CHEAL; corn, Zea mays L. Additional index words: Herbicide resistance. Abbreviations: OM, organic matter; POST, postemergence; PRE, preemergence; TR-CHEAL, triazine-resistant common lambsquarters.