CONTROL OF STINKWEED (Thlaspi arvense) AND FLIXWEED (Descurainia sophia) IN WINTER WHEAT (Triticum aestivum)

Field studies were conducted from 1986 through 1989 at Lethbridge, Alberta to determine suitable herbicides applied in either fall or spring for the selective control of stinkweed (Thlaspi arvense L.) and flixweed [Descurainia sophia (L.) Webb] in winter wheat (Triticum aestivum L.). Herbicides generally controlled these weeds better when applied in fall than in spring. Weeds emerging in the spring reduced the overall effectiveness of non-residual fall treatments. Superior control and greatest crop yields were attained with herbicides that controlled stinkweed and flixweed in the fall and provided residual control of spring flushes of these weeds. Fall-applied chlorsulfuron, metsulfuron methyl, metribuzin, dicamba plus 2,4-D, and picloram plus 2,4-D provided excellent initial and residual control of these weeds in all 3 yr. Winter survival of winter wheat was not affected by any treatment. Crop injury was observed only with treatments involving metribuzin and then only in 1 of 3 yr. Stinkweed and flixweed combined to reduce the yield of winter wheat by 18–32% over the 3 yr of the study.Key words: Bromoxynil, chlorsulfuron, clopyralid, dicamba, metsulfuron methyl, metribuzin, picloram, thifensulfuron, 2,4-D, MCPA