Bentazon

Abstract: Field studies were conducted at three sites in Missouri in 1986 and 1987 to evaluate the performance of below-label rates of bentazon, acifluorfen, and chlorimuron tank mixed with sethoxydim and applied to soybeans 7 and 14 days after planting to evaluate broadleaf and grass weed control and weed seed production. Sequential applications of 0.25X-labeled rates of all three broadleaf herbicides tank mixed with 0.5X sethoxydim rates controlled giant foxtail, velvetleaf, and common cocklebur equivalent to one applica- tion of standard-labeled rates of the same tank mixes. Single applications of below-labeled rates of the postemergence herbicides did not control weeds, and soybean yields were not equal to sequential 0.25X or single full-rate treatments. A preemergence treatment of clomazone plus imazaquin applied at labeled rates controlled weeds, and soybean yields were equal to a handweeded check in both years at all test locations. Weeds survived and produced seed to reinfest the plots the following year unless nearly 100% control was achieved. Nomenclature: Acifluorfen, 5- (2-chloro-4-(trifluoro- methyl)phenoxyl)-2-nitrobenzoic acid; bentazon, 3-( 1-methyl- ethyl) - (1H) -2,1,3 - benzothiadiazin - 4(3H)-one 2,2 - dioxide; chlorimuron, 2- (((((4-chloro-6-methoxy-2 -pyrimidinyl)amino carbonyll aminol sulfonyl) benzoic acid; clomazone, 2- ((2- chlorophenyl)methyll - 4,4-dimethyl-3-isoxazolidinone; imaza- quin, 2- (4,5 -dihydro- 4-methyl-4-(1 -methylethyl)-5-oxo-IH- imidazol-2 -ylJ -3 -quinolinecarboxylic acid; sethoxydim, 2-(1- (ethoxyimino)butyl) -5- (2 -(ethylthio)propyll -3-hydroxy- 2-cy- clohexen-l-one; common cocklebur, Xanthium strumarium L.