Field studies were conducted from 1997 to 1999 in Westminster, MD, to evaluate a variety of preemergence (PRE) and postemergence (POST) herbicide programs on crop injury and control of triazine-resistant common lambsquarters (TR-CHEAL) in no-till corn. In 1997 PRE studies, combinations of metolachlor with flumetsulam or halosulfuron and high rates of rimsulfuron thifensulfuron (0.02 0.009 kg ai/ha) injured corn most 4 weeks after treatment (WAT), averaging 11 to 15%. In 1998 and 1999, metolachlor plus a high rate of halosulfuron (0.07 kg/ha) injured corn most 4 WAT, averaging 13 and 10%, respectively. High rates of rimsulfuron thifensulfuron also provided a higher level of corn injury in 1998 and 1999 in comparison with many of the other treatments. However, for all three years of the study, no injury was observed from any PRE treatment 8 WAT. In 1997 and 1998, at 8 WAT, combinations of metolachlor with flumetsulam or halosulfuron provided greater TR-CHEAL control than many of the other treatments, averaging 98 and 100%, respectively. In 1999, however, control of TR-CHEAL with these same treatments did not vary in comparison with most of the other treatments. At 8 WAT, there was a trend for increased TR-CHEAL control as the rates of RPA-201772 and rimsulfuron thifensulfuron increased. Control of TR-CHEAL with metolachlor atrazine pendimethalin varied across years 8 WAT. Similar observations were made 16 WAT. In 1997, POST applications of dicamba, SAN 1269H at 0.3 lb ai/ha, primisulfuron dicamba, and primisulfuron CGA 152005 dicamba provided the highest level of TR-CHEAL control 8 WAT, averaging 93, 93, 95, and 93%, respectively. In 1998, with the exception of carfentrazone atrazine, all POST treatments provided 90% control of TR-CHEAL or better 8 WAT. In 1999, POST applications of SAN 1269H at 0.3 kg/ha, pyridate atrazine, and primisulfuron CGA 152005 pyridate provided the highest level of TR-CHEAL control, averaging 80, 90, and 96%, respectively, 8 WAT. With the exception of carfentrazone atrazine, control of TR-CHEAL with the other POST treatments varied in 1999 from 60 to 74% 8 WAT. Carfentrazone atrazine applied POST provided the lowest level of TR-CHEAL control 8 WAT averaging 28, 37, and 17% for 1997 to 1999, respectively.
Nomenclature: Atrazine; carfentrazone; dicamba; flumetsulam; halosulfuron; RPA-201772 (proposed name, isoxaflutole) [5-cyclopropyl-4-(2-methylsulfonyl-4-trifluoromethyl-benzoyl)isoxazole]; metolachlor; pendimethalin; CGA 152005 (proposed name, prosulfuron) {1-(4-methoxy-6-methyltriazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)-phenylsulfonyl] urea}; rimsulfuron; SAN 1269H (formerly BAS 662H), a mixture of SAN 835H {2-[1-[[[(3,5-difluorophenyl)amino]carbonyl]hydrozono]ethyl]-3-pyridinecarboxylic acid} and dicamba in a 1:2.5 ratio; thifensulfuron methyl; common lambsquarters, Chenopodium album L. #3 CHEAL; corn, Zea mays L. Pioneer 3140.
Additional index words: Herbicide-resistant weeds.
Abbreviations: PRE, preemergence; POST, postemergence; TR-AMACH, triazine-resistant smooth pigweed; TR-CHEAL, triaizine-resistant common lambsquarters; TS-CHEAL, triazine-susceptible common lambsquarters; WAT, weeks after treatment.
