INFLUENCE OF FALL AND SPRING HERBICIDE APPLICATION ON WINTER WHEAT (Triticum aestivum L. ’NORSTAR’)

Recommendations regarding the timing of herbicide application in winter wheat vary among production areas. The current increase in area of winter wheat production in Saskatchewan warrants an examination of herbicide recommendations for this non-traditional production area. Field research was conducted for 2 yr at several locations in Saskatchewan using 2,4-D, MCPA, dicamba, bromoxynil, chlorsulfuron, and clopyralid, applied in the late fall or early spring, to determine the effects of time and rate of application on winter wheat grain yield. Winter wheat (Triticum aestivum L. ’Norstar’) was tolerant to fall application of all herbicides at rates recommended for spring application. Grain yield was reduced in some cases when double the recommended spring rate of 2,4-D, MCPA, bromoxynil, and clopyralid was applied in the fall. Spring application of clopyralid resulted in significantly lower grain yield than fall application. All herbicides tested show potential for use in winter wheat production, although caution is warranted for spring application of clopyralid.Key words: Wheat (winter), 2,4-D, MCPA, dicamba, bromoxynil, chlorsulfuron