Comparison of Total Postemergence Weed Control Programs in Soybean

Abstract

Field studies were conducted in 1994 and 1995 in central and southern Illinois to compare several total postemergence weed control programs in soybean [Glycine max (L.) Merr.]. Herbicide programs evaluated were imazethapyr (an acetolactate synthase [ALS] inhibiting herbicide) applied alone or in combination with lactofen and two non-ALS herbicide programs consisting of combinations of bentazon, acifluorfen, and sethoxydim and combinations of fomesafen, fluazifop, and fenoxyprop. These treatments were applied early postemergence (EPOST, V-1 soybean-first trifoliate) and postemergence (POST, V-2 soybean-second trifoliate). Non-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 1994 at Brownstown, broadleaf weed control was poor with non-ALS herbicide programs when weed growth stages were larger and environmental conditions more extreme than other experiments. Adding lactofen to imazethapyr increased broadleaf weed control in some instances but decreased giant foxtail (Setaria faberii L.) control. Imazethapyr plus lactofen tended to produce the greatest degree of soybean injury.