Performance of a Diflufenican-Containing Premixture in Dicamba-Resistant Soybean Systems

Abstract

Weeds belonging to the Amaranthus family are most problematic for soybean producers. With Palmer amaranth evolving resistance to multiple herbicides labeled for use in soybean, producers seek new sites of action to integrate into season-long herbicide programs. Bayer CropScience plans to launch a Convintro™ brand of herbicides, one being a premixture that will include diflufenican (WSSA Group 12), metribuzin (WSSA Group 5), and flufenacet (WSSA Group 15), for use preemergence (PRE) in soybean. Research trials were conducted in Fayetteville and Keiser, AR, and Holt, MI, in 2022 and 2023 to evaluate the premixture in a season-long program in a dicamba-resistant soybean system. A 0.17:0.35:0.48 of the diflufenican:metribuzin:flufenacet (DFF-containing) premixture was applied PRE with different combinations of glyphosate, glufosinate, dicamba, and acetochlor at 28 [early-postemergence (EPOST)] and 42 [late-postemergence (LPOST)] days after planting (DAP). At the EPOST timing, the DFF-containing premixture provided >90% Palmer amaranth and prickly sida control. However, common ragweed, common lambsquarters, morningglory ssp., and annual grass control was ≤80% at this timing. When the LPOST applications occurred, treatments that had already received an EPOST application controlled prickly sida, morningglory ssp., Palmer amaranth, and annual grasses greater than those that had not, indicating the PRE application of the DFF-containing premixture was not sufficient to provide control of the weed spectrum through 42 days after planting. By 70 days after planting, all programs provided ≥93% control of all weeds evaluated. Herbicide programs that utilized the DFF-containing premixture PRE fb EPOST fb LPOST controlled common ragweed, common lambsquarters, morningglory ssp., and annual grasses greater than the one pass postemergence systems. In addition, all herbicide programs evaluated reduced Palmer amaranth seed production by >99%. However, producers that plan to utilize the DFF-containing premixture may need two postemergence herbicide applications to obtain high levels of weed control throughout the growing season.