Due to the limited availability of selective herbicides to control Sumatran fleabane after soybean emergence, it is essential to develop new options that provide effective control prior to planting. A new herbicide formulation containing diclosulam halauxifen-methyl was evaluated for effectiveness at two Sumatran fleabane plant heights (5 to 10 cm, and 10 to 50 cm) and for soybean selectivity when applied at 7 or 3 d before planting. Combined results from the two sites showed that diclosulam halauxifen, applied either alone or in a tank mixture with glyphosate, and the tank mixture of diclosulam 2,4-D amine glyphosate are effective at all rates tested to control Sumatran fleabane in preplant applications. Crop response was observed with applications 7 days before planting at only one of the sites. A rate-dependent crop response was observed for pre-plant applications performed 3 days before soybean planting. However, crop yield was not significantly affected for either timing across all rates. All rates tested of diclosulam halauxifen in this study were considered safe to soybean.
Nomenclature: Diclosulam; glyphosate; halauxifen, 4-amino-3-chloro-6-(4-chloro-2-fluoro-3-methoxyphenyl)pyridine-2-carboxylic acid; 2,4-D; Sumatran fleabane, Conyza sumatrensis (Retz.) E. Walker; soybean, Glycine max L. Merr.