Christopher J Voglewede

Sumatran Fleabane (Conyza sumatrensis) Control in No-Tillage Soybean with Diclosulam Plus Halauxifen-Methyl

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.