INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT DOWNY BROME (CHEATGRASS)
(Bromus tectorum)


Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, Oregon
INTRODUCTION DOWNY BROME (CHEATGRASS)
Downy Brome (Cheatgrass) (Bromus tectorum) is a monocot weed in the Poaceae family.  In Oregon this weed first evolved resistance to Group 2 (Legacy B) herbicides in 1997 and infests Kentucky bluegrass.   Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to imazamox, primisulfuron-methyl, and sulfosulfuron and they may be cross-resistant to other Group 2 (Legacy B) herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

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QUIK STATS (last updated Jun 16, 2003 )

Common NameDowny Brome (Cheatgrass)
SpeciesBromus tectorum
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesimazamox, primisulfuron-methyl, and sulfosulfuron
LocationUnited States, Oregon
Year1997
Situation(s)Kentucky bluegrass
Contributors - (Alphabetically)Daniel Ball, George Mueuller-Warrant, and Kee-Woong Park 
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Daniel Ball
Madras Research farm.

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RESISTANCE RATIO

Daniel Ball
only 3x

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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Downy Brome (Cheatgrass) biotype with this Downy Brome (Cheatgrass) biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.
 
Genetics

Genetic studies on HRAC Group 2 resistant Downy Brome (Cheatgrass) have not been reported to the site.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature
 
Mechanism of Resistance

Studies on the mechanism of resistance of Group 2 (Legacy B) resistant Downy Brome (Cheatgrass) from Oregon indicate that resistance is due to enhanced metabolism.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
 
Relative Fitness

Researchers have indicated that Group 2/B resistant Downy Brome (Cheatgrass) is ecologically less fit than normal susceptible Downy Brome (Cheatgrass).  There may be a note below or an article discussing the fitness of this biotype in the Fact Sheets and Other Literature
 
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CONTRIBUTING WEED SCIENTISTS

DANIEL BALL
Professor Of Weed Science
Oregon State University
Columbia Basin Agricultural Research Center
48037 Tubbs Ranch Road P. O. Box 370
Pendleton, 97801, Oregon
United States
Email Daniel Ball
Web   : Web Site Link
GEORGE MUEULLER-WARRANT
Research Agronomist
USDA-ARS
Department of Crop and Soil Science
Crop and Soil Science Bldg.
Corvallis, 97331, Oregon
United States
Email George Mueuller-Warrant
Web   : Web Site Link
KEE-WOONG PARK
Professor
Chungnam National University
Department Of Crop Science
99 Daehak-ro
Yuseong-gu
Daejeon, 305-764, Oregon
South Korea
Email Kee-Woong Park
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Oregon have been instrumental in providing you this information. Particular thanks is given to Daniel Ball, George Mueuller-Warrant, and Kee-Woong Park for providing detailed information.
Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
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Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Alberta) CanadaAlberta2021 Canola glyphosate 7 Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)
40Bromus tectorumDowny Brome (Cheatgrass)21234
2 FranceFrance 1981 Corn (maize) atrazine 17 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
40Bromus tectorumDowny Brome (Cheatgrass)457
3 SpainSpain 1990 Wheat chlorotoluron 38 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
40Bromus tectorumDowny Brome (Cheatgrass)190
4 SpainSpain 1990 Orchards simazine 38 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
40Bromus tectorumDowny Brome (Cheatgrass)191
5 United States (Oregon) United StatesOregon1997 Kentucky bluegrass imazamox, primisulfuron-methyl, and sulfosulfuron 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
40Bromus tectorumDowny Brome (Cheatgrass)1112
6 United States (Oregon) United StatesOregon2005 Grass seed clethodim, fluazifop-butyl, quizalofop-ethyl, and sethoxydim 45 Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
40Bromus tectorumDowny Brome (Cheatgrass)5375
7 United States (Montana) United StatesMontana2016 Wheat imazamox, procarbazone-Na, and pyroxsulam 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
40Bromus tectorumDowny Brome (Cheatgrass)15071
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