Field experiments were conducted to evaluate the tolerance of 79 winter wheat cultivars to cyanazine, BAY SMY 1500, and metribuzin. When known, the pedigree of the more cyanazineand BAY SMY 1500-tolerant hard red winter cultivars included ‘Hope’ and/or ‘Cheyenne’ parentage. However, the cultivars more sensitive to BAY SMY 1500, notably those with ‘Vona’ parentage, were not consistently sensitive to cyanazine. Visible injury on the hard red and soft red winter cultivars did not consistently indicate yield reductions. The soft red winter cultivars, compared to the hard red winter cultivars, were generally more sensitive to cyanazine than BAY SMY 1500.

Diuron, simazine, and terbacil were applied together or separately in the field each May from 1981 through 1996. Weed control was over 90% in 1981 and 1982, but by 1984 weeds increased in plots treated with diuron and simazine. Weed abundance was relatively low from 1981 through 1996 in plots treated with terbacil. Broadleaf and grass species abundance was similar in most herbicide-treated plots from 1992 through 1996. Perennial species, particularly fescue (Festuca arundinacea) and ailanthus (Ailanthus altissima), dominated sites treated with diuron and simazine. The weed community changed within 3 yr of the implementation of the weed management program that relied solely on herbicides. A relatively stable weed community persisted from 1992 through 1996. Repeated use of the combined high rate of diuron and low rate of terbacil provided excellent weed control for 15 yr.