Full TGIF Record # 224845
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Web URL(s):http://www.wsweedscience.org//wp-content/uploads/proceedings-archive/1999.pdf#page=33
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Author(s):Mueller-Warrant, George W.; Mallory-Smith, Carol A.; Hendrickson, Paul E.
Author Affiliation:Mueller-Warrant: Research Agronomist, USDA-ARS, National Forage Seed Production Research Center; Mallory-Smith: Assistant Professor; Hendrickson: Faculty Research Assistant, Department of Crop and Soil Science, Oregon State University, Corvallis, OR
Title:Primisulfuron resistance in downy brome
Section:Poster session
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Meeting Info.:Colorado Springs, Colorado: March 8-11, 1999
Source:1999 Proceedings of the Western Society of Weed Science. Vol. 52, 1999, p. 16.
# of Pages:1
Publishing Information:Newark, California: Western Society of Weed Science
Keywords:TIC Keywords: Bromus tectorum; Herbicide combinations; Herbicide evaluation; Herbicide resistance; Poa pratensis; Primisulfuron; Weed control
Abstract/Contents:"Downy brome is a major weed of Kentucky bluegrass grown for seed in the Pacific Northwest, and reductions in field burning are likely to exacerbate problems with this species. Tank mixes and sequential applications of primisulfuron plus terbacil generally provided 98 to 100% control of downy brome in long-term residue management by herbicide treatment studies with Kentucky bluegrass in central and eastern Oregon. However, by 1996 downy brome control in a few plots that had been treated with primisulfuron plus terbacil for 3 consecutive years was noticeably poorer than it had been in previous years. Whether downy brome survival in those plots was due to sprayer skips, different weather patterns, or increased resistance to herbicides was not clear. For the 1996 to 1997 growing season, uniform herbicide treatments were imposed on most of the existing plots, leaving three out of 15 plots in each residue management block as untreated checks. The other 12 plots received early fall treatment with primisulfuron plus terbacil followed by late fall treatment of either primisulfuron plus terbacil or primisulfuron alone where stands were thin. Samples of downy brome seed had been collected and archived during cleaning of Kentucky bluegrass seed harvested from 1994 to 1997, and a 55 plot subset of these samples was screened in the greenhouse for resistance to 39 g ha-1 primisulfuron applied at the 2-leaf growth stage. Average downy brome survival increased from 6% for seed harvested in 1994, to 8% for 1995, and to 20% for 1996. Dose response curves were generated for seed harvested from three plots at Madras in 1996, and the LD98% for the most resistant type was 7-fold greater than for the most susceptible type. Primisulfuron-resistant types were cross resistant to sulfosulfuron and imazamox at roughly similar levels of increased resistance. Acetolactate synthase activity in all three biotypes plus another known susceptible was similarly inhibited by imazapyr and chlorsulfuron (Dale Shaner, pers. comm.), implying that resistance was not target-site based. Phytotoxicity of sulfosulfuron on the resistant types was dramatically increased by tank-mixing with an organophosphate insecticide, implying that resistance was based on metabolic degradation of sulfonylurea herbicides. Progression of symptoms on primisulfuron-treated downy brome included a rapid cessation of growth and a gradual discoloration of the treated leaves, followed by the appearance of new tillers at the base of the plant within two weeks on the resistant biotypes."
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ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Mueller-Warrant, G. W., C. A. Mallory-Smith, and P. E. Hendrickson. 1999. Primisulfuron resistance in downy brome. Proc. West. Soc. Weed Sci. 52:p. 16.
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