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Publication

Sensitivity of winter wheat (Triticum aestivum L.) to quizalofop-p-ethyl in central Oklahoma and Kansas

Childers, Justin Tanner
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Abstract

CoAXium® Wheat Production System, developed by Colorado Wheat Research Foundation, Albaugh Chemical, and Limagrain, is a new herbicide tolerant wheat that allows for the use of Aggressor^TM herbicide [active ingredient: quizalofop-p-ethyl (quizalofop)] for control of grassy weeds. An increase in applications of quizalofop may increase the likelihood of physical drift and/or tank contamination to nearby sensitive plants, including wheat that is not tolerant to quizalofop. To further evaluate this challenge, a trial was conducted at four locations in the central Great Plains, during the 2018-2019 and 2019-2020 growing seasons. Five quizalofop rates were used: 1X (92 g ai ha-1), 1/10X, 1/50X, 1/100X, and 1/200X, along with two different application timings: 2- 3-leaf (fall) and 3- 4-tiller (spring). Visual injury was evaluated every two weeks throughout the growing season, along with the collection of end-of-season biomass, harvest index, and grain yield. For yield, herbicide rate by application timing interaction was significant for half of the site years. At the other four site years, a herbicide rate main effect was observed. For the interaction, regardless of application timing, the field-use rate 1X resulted in complete crop loss or near crop loss. For the 1/10X rate with the fall application, yield loss ranged from 0 to 39% whereas with the spring application, loss ranged from 80 to 100%. No significant yield reduction was observed following the three lowest rates, except for Stillwater 2019 and 2020, then Perkins in 2019. At Stillwater there was an 11% reduction in yield at the 1/200X rate in 2019, and 20% yield reduction at the 1/50X rate in 2020. Perkins 2019 also had an 8% yield reduction followed the 1/50X rate When rate was a significant main effect, all 1/10X applications led to 86 to 100% yield loss. There was no significant visual injury or yield loss with the three lowest rates with the exclusions above. The environment had a substantial impact on wheat response with the 1/10X rate. Minimal response was most likely when it was cold and dry before and after application because wheat plants were not actively growing, thus not translocating the herbicide effectively.

Date
2020-12
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