Field experiments were conducted to identify herbicides for selectively controlling foxtail barley seedlings in spring wheat and flax. ICIA0604, fenoxaprop-P/safener, CGA184927/safener, metribuzin, and MON37500 in wheat and sethoxydim, clethodim, quizalofop, fluazifop-P, and the mixture of fluazifop-P/fenoxaprop-P in flax were applied at the three- to four-leaf and one- to three-tiller stages of foxtail barley. MON37500 was the only herbicide tested in wheat that provided excellent control of foxtail barley and a high degree of crop tolerance. MON37500 at 13 to 19 g/ha applied at the early growth stage controlled foxtail barley but rates of 25 to 30 g/ha were needed at the later growth stage. In flax, quizalofop was the most efficacious herbicide on foxtail barley. Sethoxydim and clethodim sometimes provided weed control similar to that of quizalofop when applied at the three- to four-leaf stage, but quizalofop was always more effective at the one- to three-tiller stage of foxtail barley. Wheat and flax yields were greater when effective herbicides were applied at the early than at the late stage, indicating the need for early control of foxtail barley to minimize weed competition. MON37500 in wheat and quizalofop in flax provide growers with highly efficacious herbicide options for in-crop control of foxtail barley in conservation tillage systems.

Studies were conducted to determine the effect of ensiling and/or rumen digestion by cattle on the germination and viability of several common weed species. Seed survival of grass species subjected to ensiling and/or rumen digestion tended to be less than that of broadleaf species. Downy brome, foxtail barley, and barnyardgrass were nonviable after either ensiling for 8 weeks or rumen digestion for 24 h. Some green foxtail (17%) and wild oats (0 to 88%) seeds survived digestion in the rumen but were killed by the ensiling process. Varying percentages of seeds of kochia, redroot pigweed, common lambsquarters, wild buckwheat, round-leaved mallow, and field pennycress remained viable after ensiling (3 to 30%), rumen digestion (15 to 98%), and ensiling plus rumen digestion (2 to 19%). A time course study of rumen digestion indicated that loss of seed viability often was not a gradual process. With some species, there was an initial lag phase while degradation of the protective seed coat likely occurred, followed by a rapid decline in embryo viability. The diet fed to livestock appeared to affect viability losses caused by rumen digestion. Estimates of seed survival with varying rates of passage through the rumen due to differing ratios of grain to forage in the diet are presented.

Primary tillage is an inexpensive method to control foxtail barley, a perennial bunchgrass which is an increasing concern to no-till cereal farmers in the Northern Great Plains. Moldboard plowing or chisel plowing in fall followed by field cultivation-harrowing in spring effectively controlled established foxtail barley on previously untilled sites before planting spring wheat. In contrast, chisel plowing in spring followed by field cultivation-harrowing did not control this weed completely.

The spread of perennial weeds, such as foxtail barley, is a prime deterrent to adoption of no-till cereal production in the Northern Great Plains. In a 3-yr study, the isopropylamine salt of glyphosate at 0.56 kg ai/ha plus nonionic surfactant at 0.25% (v/v) did not control established perennial foxtail barley in early spring. However, adding ammonium sulfate at 2.8 kg/ha to glyphosate plus surfactant improved the effectiveness and year-to-year consistency of glyphosate for killing this weed. This spring treatment fits into no-till farm practice in the Northern Great Plains, providing no-till farmers with a defined strategy to manage this perennial bunch-grass weed.

A 4-yr field experiment was conducted to determine the merits of combining cultural and chemical controls to manage foxtail barley in reduced-tillage systems. Factors studied were crop row spacing, seeding rate, and application rate and timing of glyphosate within a spring wheat-flax cropping sequence. Glyphosate applied preseeding at 400 or 800 g/ha killed foxtail barley seedlings but only suppressed established perennial plants. Glyphosate applied postharvest at 800 g/ha killed 60 to 70% of established plants. Combinations of preseeding and postharvest glyphosate gave the greatest reductions in foxtail barley biomass and seed production and resulted in the greatest increases in crop yield. Including flax in the rotation allowed use of grass herbicides such as quizalofop or sethoxydim that effectively controlled foxtail barley seedlings and provided some suppression of perennial plants. An increase in wheat seeding rate from 75 to 115 kg/ha reduced foxtail barley growth and increased wheat yield in 3 of 4 yr. Increasing the flax seeding rate from 40 to 80 kg/ha or reducing wheat and flax row spacing from 30 to 20 cm provided little benefit in managing foxtail barley or increasing crop yield. A multiyear approach combining agronomic practices and timely use of herbicides should allow growers to effectively manage foxtail barley in annual cropping systems using conservation tillage.

In commercial fields of creeping red fescue, spring applications of sethoxydim at 500 g/ha and fluazifop-P at 250 g/ha consistently reduced the heading, and consequently the seed production, of foxtail barley and volunteer bromegrass by ≥90% without affecting crop seed yield, 100-seed wt or germination. The effectiveness of sethoxydim at 500 g/ha and fluazifop-P at 250 g/ha to reduce heading of grass weeds was not affected by tank mixing with metsulfuron at 4.5 g/ha but was reduced when tank mixed with either dicamba plus 2,4-D at 280 plus 560 g/ha or 2,4-D alone at 560 g/ha. Metsulfuron alone, or in tank mixtures with sethoxydim (500 g/ha) or fluazifop-P (250 g/ha), effectively controlled dandelion and volunteer alsike clover (probability of ≥80% control was 0.94 or more). Dicamba plus 2,4-D provided a similar level of volunteer alsike clover control but was less effective on dandelion, while 2,4-D was ineffective on both weeds. Treatments containing dicamba plus 2,4-D reduced crop seed yield and germination, and increased seed weight.