Classification of Trifludimoxazin + Saflufenacil and Pyroxasulfone Herbicide Interaction for the Control of False Cleavers (Galium spurium) and Wild Oat (Avena Fatua)
Date
2022-03-08
Authors
Aldridge, Kathryn
Johnson, Eric
Shirtliffe, Steve
Bertholet, Ethan
Oostlander, Mark
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Conference Presentation
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Abstract
Herbicide-resistant (HR) weeds continue to develop, requiring alternative herbicide mechanisms of action (MOA) to examine weed control. The first objective of this study was to examine the herbicide interaction between trifludimoxazin + saflufenacil (Group 14) and pyroxasulfone (Group 15) in false cleavers and wild oat. The second objective was to determine the type of herbicide interaction present, whether that be additive, synergistic, antagonistic, or no effect. This study was repeated twice for each weed species in the phytotron facility at the University of Saskatchewan. Treatments comprised of two factors (herbicide group and rate) and were applied in a randomized complete block design (RCBD) with four replicates. The false cleaver treatments consisted of ten different rates (0.027778 – 16x, increasing in 2x increments) of BAS85100H (2:1 pre-mix of saflufenacil and trifludimoxazin (0.5, 1.125, 2.25, 4.5, 9, 18, 36, 72, 144, 288 g ai h-1) and pyroxasulfone (1.666667, 3.75, 7.5, 15, 30, 60, 120, 240, 480, 960 g ai ha-1) applied alone and as a tank-mix. The wild oat treatments consisted of nine different rates (0.125 – 32x, increasing in 2x increments) of BAS85100H (2.25, 4.5, 9, 18, 36, 72, 144, 288, 576 g ai h-1) and pyroxasulfone (7.5, 15, 30, 60, 120, 240, 480, 960, 1920 g ai ha-1) applied alone and as a tank-mix. Additional treatments included an untreated check. Herbicide efficacy ratings were taken 7, 14, and 21 days after emergence (DAE). A 3-parameter log-logistic model was selected to model each weed species’ biomass. For false cleavers, Group 14+15 had the lowest ED50, the effective dose required to reduce the biomass present by 50%, at a 0.57x rate. Group 15 had the lowest ED50 at a 0.27x rate for wild oat but was not significantly different from Group 14+15. Colby’s analysis compared the expected versus observed plant responses to classify the herbicide interactions for each weed species. A 3-parameter log-logistic model was selected for both weed species, with all model parameters being non-significant. This result indicated an additive herbicide relationship as the control for the herbicide mixture was equal to what was expected based on the efficacy of the two individual herbicide groups. Therefore, a tank-mix of Group 14+15 herbicides improves false cleavers control compared to the individual applications. Colby’s analysis suggested an additive response for wild oat; however, the response was similar to Group 15 individually, and the addition of Group 14 provided only marginal improvement in control. Results indicated that using tank-mixtures improved HR weed management for both false cleavers and wild oat.
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Herbicide Resistance, False Cleavers, Wild Oat
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Soils and Crops Workshop