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Long-term control of downy brome with an integrated approach is needed in order to sustain range productivity. Studies were conducted to study the effectiveness of a combination of downy brome control practices. In two studies, glyphosate and paraquat were evaluated at various rates for up to three successive years for control of downy brome in rangeland. A third study evaluated the competitiveness of perennial cool-season grasses against downy brome in the absence of herbicides. Glyphosate, at 0.55 kg/ha, and 0.6 kg/ha paraquat provided selective downy brome control on rangeland when applications were combined with intensive grazing. Downy brome control was greater than 90% following two sequential years of 0.6...
Species lists are important tools for managing biodiversity, including controlling nonnative species, but they are either incomplete or lacking for many areas. Our objective was to illustrate how the synergy of disparate data sets can increase knowledge of species distributions while minimizing further field expenditures. We compared five different data types (two species lists, weed surveys, vegetation plots, and weed maps) of nonnative plant locations at the county level from 45 data sets covering Colorado. Species lists captured the highest number of species, but they missed many of the noxious weeds recorded by weed-mapping data. The number of species recorded per county increased by 30% on average with data...
This study characterized seedling emergence of downy brome from August to early December over a 6-yr period. Seedlings were counted weekly in quadrats established in winter wheat stubble at Akron, CO. Seedling emergence varied among years, which was caused by erratic seasonal precipitation. Producers delay planting of winter wheat to reduce downy brome density in the crop, but in only 1 yr out of 6 would producers have benefited from this control strategy. Furthermore, delayed planting has negative crop consequences: less grain yield and more susceptibility to plant diseases and wind erosion because of less fall plant growth. Because fall precipitation is erratic in the semiarid Great Plains, other control strategies,...
Field studies were conducted for two years at two locations near Pendleton and Moro, OR to evaluate the influence of single sub-surface nitrogen (N) fertilizer application timings and multiple N applications on downy brome and winter wheat growth and yield. N applications in fallow, at planting, during the crop season, and several split N application timings were compared to evaluate downy brome interference in winter wheat. N application rates varied between locations as a function of average annual precipitation and accepted agricultural practice. Pendleton and Moro were considered high and low precipitation sites, respectively. At Pendleton in a year of above average precipitation, N applied at planting, in-crop,...
Experiments were conducted at Bridgeport, NE, during 1983 through 1987 to select alternatives for silvex and 2,4,5-T for sand sagebrush and brittle pricklypear control. Of the six herbicides examined, the butoxyethyl ester of 2,4-D at 2.2 kg ae/ha was equivalent to the propylene glycol butyl ether ester of silvex or 2,4,5-T for sand sagebrush control. The potassium salt of picloram at 0.3 kg ae/ha was equal to silvex for brittle pricklypear control. Published in Weed Technology, volume 3, issue 2, on pages 272 - 274, in 1989.
The effects of five soil fungi, endemic to the western United States, were evaluated for disease reaction, root dry weights and shoot dry weights on five grass species. The undesired grass, downy brome or medusahead, the perennial forage species, squirreltail or western wheatgrass, and winter wheat were susceptible to take-all. Downy brome, medusahead, squirreltail, and winter wheat were susceptible to crown rot. The desired grasses, squirreltail, western wheatgrass, and winter wheat, were susceptible to barepatch. Crown rot is adapted to dry soils and may be a potential biological control on downy brome and medusahead in the arid environment of the western U.S. Published in Weed Technology, volume 9, issue 2, on...
Phytotoxins produced by the naturally-occurring rhizobacterium, Pseudomonas fluorescens strain D7 (strain D7), in shake cultures from several media sources adversely affected downy brome at several growth stages and affected seeds, whole plants, and isolated cells. These uncharacterized phytotoxins inhibited root and shoot growth of downy brome by 80% in a seed germination agar assay at 2 and 400 ng total solids/ml, respectively. In a hydroponics assay, downy brome and winter wheat dry weights were reduced 50% by cell-free broth concentrations of 15 and 26% of the initial broth concentration, respectively, indicating an almost 2× selectivity between winter wheat and downy brome. Plant water use was reduced similarly....