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Horseweed (Conyza canadensis) management in Oklahoma winter wheat

Published online by Cambridge University Press:  09 October 2019

Jodie A. Crose*
Graduate Research Assistant, Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK, USA
Misha R. Manuchehri
Assistant Professor and State Extension Weed Science Specialist, Department of Plant and Soil Science, Oklahoma State University, Stillwater, OK, USA
Todd A. Baughman
Professor, Institute for Agricultural Biosciences, Oklahoma State University, Ardmore, OK, USA
Author for correspondence: Jodie Crose, Graduate Teaching Assistant, Sheridan Research and Extension Center, University of Wyoming, 3401 Coffeen Avenue, Sheridan, WY, 82801. Email:


Halauxifen plus florasulam, thifensulfuron plus fluroxypyr, and bromoxynil plus bicyclopyrone are three, relatively new POST premix herbicides developed for control of broadleaf weeds in winter wheat. These herbicides, along with older products, were evaluated for their control of horseweed in Altus, Perkins, and Ponca City, Oklahoma, during the spring of 2017 and 2018. Horseweed has become a critical weed in Oklahoma because of its extensive germination window, changes in tillage practices, and increase in herbicide-resistant horseweed biotypes. Visual weed control was estimated every 2 wk throughout the growing season and wheat yield was collected from three of the six site-years. Horseweed size ranged from 5 to 20 cm at time of application. The halauxifen plus florasulam, and thifensulfuron plus fluroxypyr combinations were effective at controlling a wide range of horseweed rosette sizes across all locations, whereas control with other treatments varied depending on presence of herbicide resistance, weed size at time of application, and mix partner.

Research Article
© Weed Science Society of America, 2019

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