The goal of this research was to determine whether crop management practices could substitute for a herbicide for managing mixed populations of green and yellow foxtail in hard red spring wheat. Crop yield and foxtail growth were measured in two years of field research in North Dakota. Spring wheat yields were as great or greater when early seeding date or 2× seeding rate were substituted for POST diclofop3 at 0.75 kg ai ha−1 for managing foxtail in spring wheat. Yield of spring wheat competing with foxtails was greater for the high seeding rate (2× = 270 kg ha−1) than both the normal (1× = 130 kg ha−1) and low (0.5× = 70 kg ha−1) seeding rates for early or middle seeding dates, but not for the late seeding date. For both early and middle seeding dates, wheat yield at the 2×seeding rate without diclofop was equal to or greater than that of the 1× seeding rate with diclofop. Late-seeded wheat did not yield well in competition with dense foxtail stands for any treatment combination. Early and middle seeding dates favored the relative increase of green foxtail over yellow foxtail in wheat, whereas late seeding favored yellow foxtail over green foxtail. Economic analysis demonstrated that early seeding date was the most critical factor in determining the stochastic dominance of treatments without diclofop over treatments with diclofop. Seeding rate was much less important than seeding date in determining the ranking of treatments in stochastic dominance analysis.

Greenhouse studies were conducted to evaluate the effectiveness of Kinetic, a silicone adjuvant that appeared to increase the efficacy and rainfastness of the isopropylamine salt of glyphosate on velvetleaf, sicklepod, barnyardgrass, guineagrass, yellow foxtail, and yellow nutsedge. Simulated rainfall of 1.3 cm in 5 min at 15 and 60 min after herbicide treatment reduced glyphosate efficacy on all weeds. Kinetic enhanced glyphosate efficacy when yellow nutsedge and guineagrass were subjected to post-spray rainfall at 60 min. On velvetleaf, sicklepod, and yellow foxtail, Kinetic improved glyphosate efficacy when the critical rain-free period was reduced to 15 min. Kinetic failed to provide rainfastness for barnyardgrass, thereby indicating a specificity of Kinetic for certain weed species.

The effect of urea ammonium nitrate (UAN) on the antagonism of sethoxydim, haloxyfop, or the methyl ester of haloxyfop activity by bentazon was evaluated in greenhouse and field trials on yellow and giant foxtail. Including UAN in the spray solution in the absence of bentazon did not enhance the activity of any of the three grass herbicides. However, adding UAN to sethoxydim or haloxyfop in the presence of bentazon decreased the bentazon antagonism of grass activity. Conversely, UAN increased bentazon antagonism of the activity of haloxyfop methyl ester. The differential effect of UAN was not linked to effects on spray solution pH.

Experiments were conducted in the greenhouse and the field to determine the influence of various oil adjuvants on small grain and grass weed susceptibility to foliarly applied BAS-514 OO H (BAS-514). Barnyardgrass, green foxtail, and yellow foxtail were more susceptible to BAS-514 at 0.56 kg ai ha-1 applied with than without an oil adjuvant. Shoot fresh weight reductions of barnyardgrass, green foxtail, and yellow foxtail were greater when BAS-514 at 0.56 kg ha-1 was applied with a methylated seed oil than with a petroleum oil adjuvant in the greenhouse. Differences in the effectiveness among oil adjuvants in enhancing BAS-514 phytotoxicity were more evident in greenhouse than in field experiments. Oil adjuvant enhancement of BAS-514 varied with plant species. Oats, hard red spring wheat, and winter wheat tolerated BAS-514 at 1.1 kg ha-1 foliarly applied with or without an oil adjuvant in the greenhouse. BAS-514 at 0.56 kg ha-1 applied with oil adjuvants caused less than 5% injury to wheat in the field.

Chlorsulfuron or metsulfuron applied POST at 10 g ai ha–1 at the four-leaf stage prevented yellow foxtail from forming seed, whereas seed production per pot was 53 to 77% of untreated checks following POST tribenuron or CGA-131036 treatments in greenhouse experiments. Chlorsulfuron applied POST at the two- and four-leaf stage severely reduced total seed production of yellow foxtail primarily by increasing plant mortality, rather than only reducing seed production per plant. Chlorsulfuron at 10 g ha–1 applied at the six- and eight-leaf stages decreased total seed production less than at the two earlier stages, by reducing both plant mortality and seed production per surviving plant. Yellow foxtail was much more susceptible than green foxtail to either chlorsulfuron or metsulfuron.

Seedling timothy tolerated fenoxaprop at 0.09 kg ai ha-1 whereas seedling orchardgrass tolerated applications as high as 0.13 kg ai ha-1. Several fenoxaprop treatments increased perennial grass yields the year following establishment. Fenoxaprop appears to solve annual foxtail problems in new plantings of orchardgrass or timothy seeded alone. Over a 2-yr period, alfalfa yields in on alfalfa-grass mixture were maintained or increased from fenoxaprop applied the seedling year. In the mixtures, timothy yield declined in relation to fenoxaprop applied, but orchardgrass did not. Use of fenoxaprop on seedling alfalfa-timothy or alfalfa-orchardgrass mixtures is questionable.