COMPARISON OF TOTAL POSTEMERGENCE WEED-CONTROL PROGRAMS IN SOYBEAN

Field studies were conducted in 1994 and 1995 in central and southern Illinois to compare several total postemergence weed control programs in soybean [Glycine mm (L.) Merr.]. Herbicide programs evaluated were imazethapyr (an acetolactate synthase [ALS] inhibiting herbicide) appl ied alone or in combination with lactofen and two non-ALS herbicide pr ograms consisting of combinations of bentazon, acifluorfen, and sethox ydim and combinations of fomesafen, fluazifop, and fenoxyprop. These t reatments were applied early postemergence (EPOST, V-1 soybean-first t rifoliate) and postemergence (POST, V-2 soybean-second trifoliate). No n-ALS herbicide programs generally provide more effective weed control POST, while weed control with imazethapyr tended to be greater EPOST. Non-ALS herbicide programs applied POST provided weed control levels that were equal to imazethapyr in three out of four experiments. In 19 94 at Brownstown, broadleaf weed control was poor with non-ALS herbici de programs when weed growth stages were larger and environmental cond itions more extreme than other experiments. Adding lactofen to imazeth apyr increased broadleaf weed control in some instances but decreased giant foxtail (Setaria faberii L.) control. Imazethapyr plus laetofen tended to produce the greatest degree of soybean injury.