3 results
Herbicidal control of deathcamas (Zigadenus paniculatus)
- Clinton A. Stonecipher, Corey Ransom, Eric Thacker, Kevin Welch, Dale R. Gardner, Matt Palmer
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- Journal:
- Weed Technology / Volume 35 / Issue 3 / June 2021
- Published online by Cambridge University Press:
- 14 September 2020, pp. 380-384
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Foothill deathcamas is a bulbous, perennial, native forb found throughout the western United States. Deathcamas begins growth early in the spring. The lack of alternative forages at this time can result in livestock becoming poisoned from the consumption of deathcamas. Research on herbicides for deathcamas control is limited to work from the 1950s and 1960s that identified 2,4-D as a control agent. The objective of this study was to evaluate alternative herbicide options for deathcamas control that include 2,4-D, 2,4-D + triclopyr, quinclorac, aminopyralid, imazapic, and chlorsulfuron. We also investigated the impact of plant growth stage on deathcamas control by making herbicide applications at two growth stages. One set of plots was treated with herbicides when deathcamas was in the early vegetative stage and the second set was treated at flowering. There is some evidence that stress might affect alkaloid content; therefore, we monitored alkaloid content of treated and nontreated deathcamas. Plots were established at Mt. Sterling, UT, and Mt. Pleasant, UT. Deathcamas density was reduced in 2,4-D, 2,4-D + triclopyr, and imazapic treatments 1 and 2 yr after herbicide application (P < 0.0001). Compared with the pretreatment densities, deathcamas densities(± standard error of the mean) 2 yr after herbicide application were reduced 96% ± 1.4%, 100% ± 0%, and 98% ± 0.9% for 2,4-D, 2,4-D + triclopyr, and imazapic, respectively, at the Mt. Sterling site. At the Mt. Pleasant site, deathcamas density was reduced by 84% ± 2.8% with 2,4-D alone, whereas 2,4-D + triclopyr and imazapic provided similar density reductions as observed at the Mt. Sterling site. Steroidal alkaloid concentrations did not change in herbicide-treated deathcamas at either stage of plant growth. These data indicate that 2,4-D, 2,4-D + triclopyr, and imazapic can effectively control deathcamas in the vegetative and flowering growth stages.
Seeding Cool-Season Grasses to Suppress Broom Snakeweed (Gutierrezia sarothrae), Downy Brome (Bromus tectorum), and Weedy Forbs
- Eric Thacker, Michael H. Ralphs, Thomas A. Monaco
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- Journal:
- Invasive Plant Science and Management / Volume 2 / Issue 3 / July 2009
- Published online by Cambridge University Press:
- 20 January 2017, pp. 237-246
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Broom snakeweed (snakeweed) is an aggressive native range-weed found throughout arid and semiarid areas of the western United States, that increases following disturbances such as overgrazing, drought, or wildfire. Ecologically based strategies that include controlling snakeweed and reestablishing desirable herbaceous species are needed to restore productivity and diversity to invaded areas. The objective of this study was to compare the ability of selected introduced and native grass species and prostrate kochia (kochia) to prevent reinvasion of snakeweed, downy brome, and annual forbs following control. This field study was replicated at two sites (Howell and Nephi, Utah) within the sagebrush-steppe biome. Snakeweed and downy brome were controlled by picloram (0.25 kg/ha [0.22 lb/ac]) and glyphosate (1.5 kg/ha [1.3 lb/ac]). The seeding treatments were comprised of three introduced grasses and a mix of these species, three native grasses and a mix of these species, and kochia. The treatments were seeded into 3 by 15-m (10 by 50 ft) plots in October 2003. Frequency and biomass of seeded species, snakeweed, downy brome, other grasses, and annual forbs were measured in 2004, 2005, and 2008. Seeded species were evaluated for success of establishment and persistence, and their ability to restrict reinvasion of snakeweed, downy brome, and annual forbs. Crested wheatgrass and big squirreltail had the best initial establishment at both locations (> 75%). In contrast, kochia and Russian wildrye did not establish well at either site, and western wheatgrass did not establish well at Nephi. Snakeweed reestablishment was restricted in all treatments except the kochia treatments, in which kochia did not establish well. Frequency of downy brome increased at both sites, and annual forb frequency increased at Nephi to near 100%, but the better established grasses suppressed biomass production of these weedy species. Crested wheatgrass established best, had the greatest production, and provided greatest suppression of downy brome and annual weeds.
A Comparison of Inter- and Intraspecific Interference on Broom Snakeweed (Gutierrezia sarothrae) Seedling Growth
- Eric Thacker, Michael H. Ralphs, Thomas A. Monaco
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- Journal:
- Invasive Plant Science and Management / Volume 2 / Issue 1 / January 2009
- Published online by Cambridge University Press:
- 20 January 2017, pp. 36-44
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Broom snakeweed (snakeweed) is a native range shrub found throughout semiarid rangelands of the western United States, which increases and dominates plant communities after disturbances such as overgrazing, drought, or wildfire. The objective of this study was to compare the ability of selected grass species and prostrate kochia to restrict establishment and growth of snakeweed seedlings in potted-plant and replicated field studies within two sagebrush ecological sites. In the potted-plant studies, single snakeweed seedlings were grown with seedlings (seedling neighbor study) and established plants (established neighbor study) of three cool-season grasses (crested, pubescent, and bluebunch wheatgrass), prostrate kochia, and snakeweed at increasing densities (1, 3, 5 plants/pot). Interference from crested wheatgrass in the seedling neighbor study, and both crested and bluebunch wheatgrass in the established neighbor study, induced the greatest mortality of snakeweed seedlings, and snakeweed growth was suppressed more by interspecific (grass) than intraspecific (snakeweed) neighbors in both potted-plant studies. Snakeweed establishment was also evaluated at two field sites: Howell and Nephi, UT. Snakeweed and downy brome were controlled by picloram (0.25 kg ae/ha) and glyphosate (1.5 kg ae/ha), then three native and three introduced grasses were drill-seeded, and prostrate kochia was dribble-seeded in replicated plots (3 m by 15 m) at both sites in October 2003. Snakeweed seedlings were transplanted into seeded plots and a bare ground control plot in autumn 2004. Snakeweed mortality was greatest (73%) in crested wheatgrass plots at Howell, but there were few differences among species treatments at Nephi. Of the snakeweed seedlings that survived, there was relatively little growth in any of the seeded plots compared to those in the bare ground control plots. These results indicate that seeded cool-season grasses interfered with and reduced establishment of snakeweed seedlings.