Field experiments were conducted at the Tidewater Agric. Exp. Station, Suffolk,VAin 1988 and to evaluate imazethapyr [(±J-2-[4,5-dihydro-4-methyl-4-( 1-methylethyl)-5-oxo-1fi-imidazol-2-yl]-5-ethyl-3-pyridine-carboxylic acid]for broadleaf weed control in peanuts (Arachis hypogaea L.). Imazethapyr was applied preplant-incorporated (PPI), preemergence (PRE), at ground-cracking (GC), and postemergence (POT) at rates of 0.036, 0.071, or 0.105 kg ai ha'. Several sequential imazathapyr systems were also included. The standard of pendimethalin (Nethylpropyl)-3, 4-dimethyl-2,6-dinitrobenzenamine) PPI, metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide) PRE, and acifluorfen (5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid) plus bentazon (3-(1-methyethyl)-(lfi)-2,1,3-benzothiadiazin-4(3fi)-one 2, 2-dioxide) POT was included for comparative purposes. Imazethapyr applied either PPI or PRE at 0.071 or 0.105 kg ha' provided >90% spurred anoda (Anoda cristata (L.) Sehlecht.), control and >96% prickly sida (Sida spinosa L.), control. Eclipta (Eclipta prostrata L.) control was 95% when imazathapyr was applied PRE at 0.105 kg ha'. Greater than 90% annual morningglory (Ipomoea spp.) control was only achieved with imazethapyr applied PPI or PRE at 0.105kg ha'. The standard provided complete control of eclipta,and 51%,92%, and 94% control of spurred anoda (Anoda cristata (L.) Schlecht.), pricklysida (Sidaspinosa L.), and annual morningglories, respectively. Several imazethapyr systems yielded equivalent to the standard. Averaged across all rates, imazathapyr applied PPI 'For, Asst. Prof

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 studies in 1990 and 1991 at six locations in Georgia and one location in North Carolina evaluated AC 263,222 for weed control, peanut tolerance, and yield. AC 263,222 applied early postemergence at 71 g ai ha−1controlled bristly starbur, coffee senna, common lambsquarters,Ipomoeaspecies, prickly sida, sicklepod, smallflower morningglory, and yellow nutsedge at least 91%. AC 263,222 controlled common cocklebur 77% and Florida beggarweed from 47 to 100%. Crop injury was 4% for AC 263,222 applied once and 12% or less from two applications. Mixtures of bentazon with AC 263,222 did not improve control compared to AC 263,222 alone. Imazethapyr did not improve control of AC 263,222 systems. In several locations, bentazon reduced control of Florida beggarweed with AC 263,222 when applied in a mixture compared to AC 263,222 alone. Weed control from the standard of paraquat plus bentazon applied early postemergence followed by paraquat, bentazon plus 2,4-DB applied POST did not provide the level or spectrum of weed control as AC 263,222 systems.

Field experiments were conducted in 1988 and 1989 to evaluate imazethapyr for weed control in peanuts. Imazethapyr was applied PRE or POST at 3, 5, or 7 weeks after crop emergence (WAE) at 0.071 kg ai ha–1. Imazethapyr applied PRE controlled common lambsquarters 85%, prickly sida 92%, and a mixture of entireleaf, ivyleaf, pitted, and tall morningglory species 77%. Morningglory control was at least 91% with imazethapyr plus metolachlor PRE followed by imazethapyr plus 2,4–DB or imazethapyr plus acifluorfen at 3, 5, or 7 WAE. Yields from systems that included metolachlor plus imazethapyr PRE followed by imazethapyr plus acifluorfen, imazethapyr plus 2,4–DB, or acifluorfen plus 2,4–DB at 3 WAE were greater than yields from the handweeded check. All systems with imazethapyr plus metolachlor PRE followed by any POST treatment except imazethapyr plus acifluorfen 7 WAE provided net returns equivalent to the herbicide standard of metolachlor PRE and acifluorfen and bentazon plus 2,4–DB 3 WAE. All systems except imazethapyr PRE provided greater net returns than the handweeded weed–free check.