Comparison of a Diflufenican-Containing Premixture to Current Commercial Standards for Residual Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) Control

Abstract

With Palmer amaranth and waterhemp evolving resistance to 9 and 6 different sites of action (SOA) globally, soybean producers continue to search for new options to control the problematic weeds. Bayer CropScience has announced its intentions to launch a Convintro™ brand of herbicides, one being a three-way premixture for preemergence use in soybean. The premixture will contain diflufenican (WSSA Group 12), metribuzin (WSSA Group 5), and flufenacet (WSSA Group 15), adding a new SOA for soybean producers throughout the United States. With the anticipated launch of the premixture, research is needed to evaluate the length of residual control provided by the new herbicide. Research trials were conducted in Fayetteville and Keiser, AR, and Morrice, MI, in 2022 and 2023. A 0.17:0.35:0.48 ratio of a diflufenican:metribuzin:flufenacet (DFF-containing premixture) was applied alone and in combination with additional metribuzin and dicamba. Also, metribuzin, acetochlor, a S-metolachlor:metribuzin premixture, and a flumioxazin:pyroxasulfone:metribuzin premixture were applied preemergence. The DFF-containing premixture was more effective in reducing Palmer amaranth/waterhemp emergence than acetochlor in four of six trials at 28 d after treatment (DAT). Plots treated with DFF-containing premixture had similar Palmer amaranth and waterhemp densities to the S-metolachlor:metribuzin premixture and the flumioxazin:pyroxasulfone:metribuzin premixture at 28 DAT. By 56 DAT, Palmer amaranth and waterhemp densities in plots with the DFF-containing premixture were comparable or superior to acetochlor and metribuzin and was comparable or superior to the S-metolachlor:metrbuzin premixture in five of six sites. The addition of dicamba or metribuzin to the DFF-containing premixture did not improve performance on Palmer amaranth and waterhemp over the DFF-containing premixture at 28 or 56 DAT. Overall, the DFF-containing premixture generally provided greater or comparable control to several standard herbicides, providing growers a new preemergence-applied product for control of Amaranthus species in soybean.