Interaction of Trifludimoxazin + Saflufenacil and Pyroxasulfone for Control of False Cleavers (Galium spurium) and Wild Oat (Avena fatua)

Non-Peer Reviewed

The development of herbicide resistant (HR) weeds has led to a need for examining alternative herbicide mechanisms of action for weed control. The objectives of this study were to examine the herbicide interaction of trifludimoxazin + saflufenacil and pyroxasulfone on residual weed control in wheat, and to determine the type of herbicide interaction present: additive, synergistic, or no effect. This study was conducted at four different site locations during the 2020 growing season. Wild oat and false cleavers were cross-seeded in 2 m strips across the experimental area in a split-block design. Treatments comprising of two factors (herbicide group and rate) were applied perpendicular to the weed strips in a randomized complete block design (RCBD) with four replicates. The treatments for this study consisted of four different rates (1, 1.5, 2.0, and 2.5X) of BAS85100H (2:1 pre-mix of saflufenacil and trifludimoxazin (18, 27, 36, 45 g ai h-1) and pyroxasulfone applied alone and as a tank-mix (60, 90, 120, 150 g ai ha-1). Additional treatments included an untreated check and commercial checks of two rates of Heat Complete® (saflufenacil (18, 36 g ai h-1) and pyroxasulfone (60, 120 g ai h-1)). Crop phytotoxicity and herbicide efficacy ratings were taken 7-14, 21-28, and 36-40 days after emergence (DAE). Both herbicide group and rate were shown to be significant at p = 0.05 for each weed species. Flint’s adaptations to Colby’s equation was used to determine the relationship present between the herbicide groups. Group 15 or 14+15 displayed the highest level of wild oat control, with 70% suppression being the highest efficacy observed. Using Flint’s analysis, it could be determined that at higher rates a synergistic relationship may be present between Group 14 and 15 herbicides. The Group 14+15 treatments displayed the highest level of false cleavers control and performed significantly better than that of Group 14 and 15 alone. Flint’s analysis showed that there is an additive relationship present between the Group 14 and 15 herbicides. A comparison of the actual versus expected weed control showed that the weed control obtained for the combination treatments was almost identical to that of the expected for an additive relationship. To further examine the herbicide relationships present, the herbicide application rates in future field studies could be extended and growth chamber experiments could be conducted to gain a more precise dose response. Link to Video Presentation: https://youtu.be/NoYSrM-iRF0