EFFECT OF AC-263,222, IMAZETHAPYR, AND NICOSULFURON ON WEED-CONTROL AND IMIDAZOLINONE-TOLERANT CORN (ZEA-MAYS) YIELD

Imidazolinone herbicides injure currently available commercial field c orn cultivars; however, cultivars resistant to these herbicides have b een developed. Sicklepod, Texas panicum, and annual morningglory contr ol using AC 263,222 (36 and 72 g ai/ha), imazethapyr (36 and 72 g ai/h a), or nicosulfuron (35 g ai/ha) applied POST at 2, 4, and 6 wk after planting were evaluated in imidazolinone-tolerant corn. Studies were c onducted at Attapulgus and Plains, Georgia from 1992 through 1933, Nic osulfuron and AC 263,222 at 72 g/ha controlled Texas panicum at least 87% when applied 2 wk after planting. Imazethapyr did not consistently control Texas panicum or sicklepod, regardless of application rate. A C 263,222 at both rates and nicosulfuron controlled sicklepod at least 86% when applied 2 wk after planting; however, later application or a pplication under dry conditions generally resulted in reduced control. All herbicides controlled the entireleaf and pitted morningglory comp lex at least 84% when applied 2 wk after planting. Imidazolinone-toler ant corn was tolerant to all herbicides, regardless of rate and tintin g, and generally yielded greater when weeds were controlled early in t he season.