(Salsola tragus)

EPSP synthase inhibitors (G/9)

United States, Washington
Russian-thistle (Salsola tragus) is a dicot weed in the Chenopodiaceae family.  In Washington this weed first evolved resistance to Group G/9 herbicides in 2015 and infests Fallow.   Group G/9 herbicides are known as EPSP synthase inhibitors (Inhibition of EPSP synthase).  Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 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 Apr 08, 2019 )

Common NameRussian-thistle
SpeciesSalsola tragus
GroupEPSP synthase inhibitors (G/9)
LocationUnited States, Washington
Contributors - (Alphabetically)Ian Burke, Prashant Jha, Vipan Kumar, and Drew Lyon 
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Drew Lyon
Weed Technology 2017 31:238–251

Glyphosate-Resistant Russian-thistle (Salsola tragus) Identified in Montana and Washington
Vipan Kumar, John F. Spring, Prashant Jha, Drew J. Lyon, and Ian C. Burke

Two putative glyphosate-resistant (GR) Russian-thistle accessions were collected from fallow fields (wheat-fallow rotation): one from Choteau County, MT (MT-R), and a second from Columbia County, WA (WA-R) in summer/fall of 2015. Greenhouse and outdoor/field whole-plant dose-response studies were conducted to confirm and characterize the levels of glyphosate resistance in these GR accessions relative to known glyphosate-susceptible accessions (MT-S and WA-S from MT and WA, respectively). Based on GR50 values of the progeny plants, the MT-R accession exhibited 4.5-fold and 5.9-fold resistance to glyphosate relative to the MT-S accession under greenhouse and outdoor conditions, respectively. The WA-R accession showed 3.0- to 5.0-fold resistance relative to the WA-S accession in greenhouse experiments, and 1.9- to 7.5-fold resistance in multi-site field experiments. In a separate greenhouse study on alternative POST herbicides to control GR Russian-thistle, bicyclopyrone plus bromoxynil, bromoxynil plus fluroxypyr, bromoxynil plus pyrasulfotole, bromoxynil plus MCPA, paraquat alone, paraquat plus metribuzin, saflufenacil alone, saflufenacil plus 2,4-D, and 2,4-D plus bromoxynil plus fluroxypyr provided effective control (≥95%) and shoot dry weight reduction (up to 98%) of GR accessions. This research confirms the first global case of field-evolved GR Russian-thistle. Best management practices (BMPs); including alternative, effective herbicide programs (based on multiple mechanisms of action highlighted in this study) need immediate implementation to prevent further spread of GR or evolution of multiple HR
Russian-thistle populations in this region.

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Russian-thistle biotype with this Russian-thistle biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetic studies on Group G/9 resistant Russian-thistle 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

The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.
Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group G/9 resistant Russian-thistle from Washington please update the database.
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Associate Professor - Weed Scientist
Washington State University
Department of Crop And Soil Sciences
163 Johnson Hall PO Box 646420
Pullman, 99164, Washington
United States
Email Ian Burke
Web   : Web Site Link
Associate Professor-Weed Science
Montana State University-Bozeman
Southern Agricultural Research Center
748 Railroad Highway
Huntley, 59037, Montana
United States
Email Prashant Jha
Web   : Web Site Link
Assistant Professor-Weed Science
Kansas State University
Agricultural Research Center-Hays
1232 240th Avenue
Hays, 67601, Kansas
United States
Email Vipan Kumar
Web   : Web Site Link
Endowed Chair in Small Grains Extension and Research, Weed Science
Washington State University
Crop & Soil Sciences
PO Box 646420
Pullman, 99164-6420, Washington
United States
Email Drew Lyon
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Washington have been instrumental in providing you this information. Particular thanks is given to Ian Burke, Prashant Jha, Vipan Kumar, and Drew Lyon for providing detailed information.
Herbicide Resistant Russian-thistle Globally
(Salsola tragus)
Herbicide Resistant Russian-thistle Globally
(Salsola tragus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Russian-thistle Globally
(Salsola tragus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Saskatchewan) CanadaSaskatchewan1989 Wheat chlorsulfuron 7 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle5067
2 Canada (Alberta) CanadaAlberta2007 Spring Barley, and Wheat thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle7831
3 United States (Washington) United StatesWashington1987 Wheat chlorsulfuron 45 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle231
4 United States (Montana) United StatesMontana1987 Cropland, and Wheat chlorsulfuron 45 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle411
5 United States (Idaho) United StatesIdaho1990 Wheat chlorsulfuron 45 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle512
6 United States (Oregon) United StatesOregon1993 Wheat chlorsulfuron, metsulfuron-methyl, and triasulfuron 45 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle1173
7 United States (California) United StatesCalifornia1994 Roadsides chlorsulfuron, and sulfometuron-methyl 45 ALS inhibitors (B/2)
147Salsola tragusRussian-thistle1036
8 United States (Montana) United StatesMontana2015 Fallow, and Wheat glyphosate 45 EPSP synthase inhibitors (G/9)
147Salsola tragusRussian-thistle12032
9 United States (Washington) United StatesWashington2015 Fallow glyphosate 45 EPSP synthase inhibitors (G/9)
147Salsola tragusRussian-thistle18160
10 United States (Oregon) United StatesOregon2016 Fallow glyphosate 45 EPSP synthase inhibitors (G/9)
147Salsola tragusRussian-thistle13055
Literature about Similar Cases

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PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site. Citation:
Heap, I.  The International Herbicide-Resistant Weed Database.  Online.  Thursday, January 28, 2021 .  Available Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.