Field studies conducted in 1990 and 1991 at five locations in Georgia and one location in Virginia in 1991 evaluated imazethapyr [2-[4,5-dihydro-4-methyl-4-( l-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-py~idinecarboxylic acid] and AC 263,222 [(+)-2[4,5-dihydro-4-methyl-4-( ~-methylethyl)-5-oxo-~H-imidazol-2yl]-5-methyl-3-pyridinecarboxylic acid] for weed control, peanut tolerance, and yield. Imazethapyr and AC 263,222 applied early postemergence (EPOST) controlled smallflower morningglory Vacquemontia tamnqolia (L.) Griseb], fpomuea morningglory species, prickly sida (Sida spinosa L.), and coffee senna (Cassia occidentalis L.) greater than 90%. Imazethapyr did not control Florida begganveed [Desmodium tortuosum (SW.) DC.] or sicklepod (Cassia obtusijoolia L.) adequately, with control generally less than 40%. AC 263,222 controlled Florida begganveed greater than 92% when applied EPOST and from 54 to 100% when applied postemergence (POST). Imazethapyr applied preplant incorporated (PPI) controlled bristly starbur (Acanthospermum hispidium DC.) 89% and imazethapyr and AC 263,222 applied EPOST controlled at least 96%. Imazethapyr controlled yellow nutsedge (Cyperus esculentus L.) 83% when applied PPI and 93% as an EPOST application. AC 263,222 controlled yellow nutsedge at least 90%. Peanut yields were higher with AC 263,222 than with imazethapyr. Imazethapyr systems that included alachlor (2-chloro-N-(2,6-ðylphenyl)-N-(methoxymethyl)acetamide), lactofen ([ (+)Z-ethoxy-l-methylz o x o e thy1 5 -[ 2-chlo ro-4-( t ri fluo rom e thy1)p he noxy ] -2nitrobenzoate] + 2,4-D B [4-(2,4-dichlorophenoxy)butanoic acid], paraquat [ 1, 11-dimethyl-4,4'-bipyridinium ion] + 2,4-DB, pyridate [~-(6-chloro-3-phenyl-4-pyridazinyl)-~-octyl carbonothioate] + 2,4-DB, metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide], or 2,4-DB provided yields equivalent to AC 263,222.

Field studies conducted at six locations in Georgia and one location in Virginia evaluated imazethapyr and imazethapyr mixtures for weed control, crop tolerance, and peanut yield. Imazethapyr applied early postemergence controlled bristly starbur, coffee senna, common cocklebur,Ipomoeaspecies, jimsonweed, prickly sida, and smallflower morningglory at least 91% and controlled yellow and purple nutsedge 88 and 98%, respectively. Paraquat plus bentazon applied early postemergence did not control the aforementioned weeds as well as imazethapyr or imazethapyr mixtures. Paraquat applied with imazethapyr reduced bristly starbur control 15% compared to imazethapyr alone but did not influence control of the other species. Imazethapyr control of bristly starbur was not improved by the addition of bentazon. Sicklepod control was less than 24% with imazethapyr and was at least 58% with imazethapyr plus paraquat Imazethapyr plus paraquat controlled sicklepod better than paraquat plus bentazon at three of the four locations evaluated. Imazethapyr did not control Florida beggarweed, while imazethapyr plus paraquat controlled at least 53%. Peanut injury was minimal 30 d after application for all treatments.

Field experiments conducted at four locations in Georgia and two locations in Florida during 1992 and 1993 evaluated AC 263,222 application rates and timings, systems, and mixtures for weed control, peanut injury, and yield. All rates of AC 263,222 applied early POST (EPOST) or POST controlledIpomoeamorningglories and smallflower morningglory at least 90%, and purple and yellow nutsedge at least 81%. Florida beggarweed and sicklepod control generally was highest when metolachlor was applied PPI followed by AC 263,222 applied EPOST at 71 g/ha, AC 263,222 at 27 or 36 g/ha plus bentazon plus paraquat applied POST, or with bentazon plus paraquat applied EPOST followed by AC 263,222 applied POST at 36 or 53 g/ha. Acifluorfen and acifluorfen plus bentazon reduced Florida beggarweed and sicklepod control at several locations when applied in mixture with AC 263,222. Common ragweed and hairy indigo control were 85 to 95% with bentazon plus paraquat applied EPOST followed by AC 263,222 applied POST at 36 or 53 g/ha. Highest peanut yields were obtained with treatments providing high levels of weed control.