CoAXium® winter wheat varietal tolerance to quizalofop-P-ethyl in the southern Great Plains
Abstract
CoAXium® Wheat Production System offers postemergence control of many annual grass weeds. However, crop tolerance concerns have been raised since the technology’s introduction in 2017. To evaluate the response of wheat cultivars that contain the AXigen® (AX) trait to quizalofop-P-ethyl (QPE), a field study was conducted at Perkins and Tipton, Oklahoma and Hays, Kansas. Two QPE treatments, 1X rate (92 g ai ha⁻¹) and 2X rate (185 g ai ha⁻¹) were applied to cultivars at three timings: fall (three to five-leaf wheat), early spring (first hollow stem), and late spring (second node detectable) along with nontreated control. A total of six CoAXium winter wheat cultivars were tested and the 2X rate was only applied in the 2021-2022 season. For the 2020-2021 season, the highest visual injury was observed on AP18 AX at Hays (26%), Perkins (50%), and Tipton (53%) among all tested winter wheat cultivars. An early spring timing reduced wheat grain yield by 8 to 9% at Perkins and 5 to 9% at Tipton as compared to nontreated and all other timings. Similarly, the late spring application of QPE at Hays reduced grain yield by 16%, 7%, and 9% compared to nontreated, fall, and early spring timings, respectively. For the 2021-2022 growing season, the fall application of QPE at 2X rate had the highest wheat biomass reduction at Perkins (35 to 67%) across all cultivars. Biomass reduction was not detected for Crescent AX. The late spring timing of QPE resulted in 12% biomass reduction for Helix AX. Furthermore, the fall application of QPE at 2X rate reduced wheat grain yield of AP18 AX by 71% at Perkins compared to all other cultivars, and QPE rates and timings. In contrast, the late spring application of QPE at 2X rate reduced wheat grain yield of Atomic AX by 53% at Hays as compared to all other cultivars, and QPE rates and timings. Altogether, these results suggest that cultivar selection, the QPE rate and application timing, as well as environment can impact tolerance ability of CoAXium® winter wheat to QPE herbicide and should be carefully considered prior to use of the technology.
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- OSU Theses [15752]