International Survey of Herbicide-Resistant Weeds

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HRAC GROUP 2 (LEGACY B) RESISTANT COMMON CHICKWEED
(Stellaria media)


Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, California
INTRODUCTION COMMON CHICKWEED
Common Chickweed (Stellaria media) is a dicot weed in the Caryophyllaceae family.  In California this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2022 and infests Triticale, and Wheat.   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 mesosulfuron-methyl, pyroxsulam, and tribenuron-methyl 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 Feb 16, 2023 )

Common NameCommon Chickweed
SpeciesStellaria media
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesmesosulfuron-methyl, pyroxsulam, and tribenuron-methyl
LocationUnited States, California
Year2022
Situation(s)Triticale, and Wheat
Contributors - (Alphabetically)Nicholas Clark, and Anil Shrestha 
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Common Chickweed biotype with this Common Chickweed 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 Common Chickweed 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 2 (Legacy B) resistant Common Chickweed from California please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

NICHOLAS CLARK
Extension Advisor
University of California
Cooperative Extension
680 N Campus Dr
Ste A
Hanford, 93230, California
United States
Email Nicholas Clark
ANIL SHRESTHA
Professor - Weed Science
California State University
Dept. Of Plant Science
2415 E San Ramon Ave. M/S AS72
Fresno, 93740, California
United States
Email Anil Shrestha
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in California have been instrumental in providing you this information. Particular thanks is given to Nicholas Clark, and Anil Shrestha for providing detailed information.
Herbicide Resistant Common Chickweed Globally
(Stellaria media)
Herbicide Resistant Common Chickweed Globally
(Stellaria media)
Drag a column header and drop it here to group by that column
Herbicide Resistant Common Chickweed Globally
(Stellaria media)
#CountryFirstYearSituationActive IngredientsSite of Action
1 BelgiumBelgium 2013 Wheat metsulfuron-methyl 3 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed10959
2 Canada (Alberta) CanadaAlberta1988 Cereals, and Wheat chlorsulfuron, ethametsulfuron-methyl, imazamethabenz-methyl, metsulfuron-methyl, sulfometuron-methyl, and thifensulfuron-methyl 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed481
3 Canada (Saskatchewan) CanadaSaskatchewan2005 Spring Barley, and Wheat thifensulfuron-methyl, and tribenuron-methyl 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5322
4 Canada (Manitoba) CanadaManitoba2008 Peas thifensulfuron-methyl, and tribenuron-methyl 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5630
5 ChinaChina 2010 Winter wheat fluroxypyr, and MCPA 9 Auxin Mimics ( HRAC Group 4 (Legacy O)
168Stellaria mediaCommon Chickweed5658
6 DenmarkDenmark 1991 Spring Barley, and Wheat chlorsulfuron, florasulam, iodosulfuron-methyl-Na, and tribenuron-methyl 13 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed86
7 FinlandFinland 2013 Spring Barley tribenuron-methyl 139 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed9946
8 FranceFrance 2012 Wheat florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, metsulfuron-methyl, and thifensulfuron-methyl 17 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5688
9 GermanyGermany 1978 Corn (maize) atrazine 18 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
168Stellaria mediaCommon Chickweed435
10 GermanyGermany 2011 Rapeseed, Spring Barley, and Wheat amidosulfuron, florasulam, imazamox, iodosulfuron-methyl-Na, mesosulfuron-methyl, nicosulfuron, pyroxsulam, thifensulfuron-methyl, tribenuron-methyl, triflusulfuron-methyl, and tritosulfuron 18 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed6744
11 IrelandIreland 1996 Cereals metsulfuron-methyl 81 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5089
12 LatviaLatvia 2016 Winter wheat amidosulfuron 174 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed15068
13 New ZealandNew Zealand 1995 Cereals chlorsulfuron 30 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed161
14 NorwayNorway 2002 Cereals iodosulfuron-methyl-Na, metsulfuron-methyl, and tribenuron-methyl 31 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5165
15 South AfricaSouth Africa 2002 Cereals chlorsulfuron, metsulfuron-methyl, thifensulfuron-methyl, and triasulfuron 37 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5193
16 SwedenSweden 1995 Spring Barley, Spring wheat, and Winter wheat chlorsulfuron, florasulam, and tribenuron-methyl 40 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed510
17 United KingdomUnited Kingdom 1985 Cereals, and Wheat mecoprop 44 Auxin Mimics ( HRAC Group 4 (Legacy O)
168Stellaria mediaCommon Chickweed358
18 United KingdomUnited Kingdom 2000 Cereals florasulam, and metsulfuron-methyl 44 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5088
19 United States (Virginia) United StatesVirginia2008 Wheat thifensulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5373
20 United States (Maryland) United StatesMaryland2009 Wheat chlorsulfuron, mesosulfuron-methyl, thifensulfuron-methyl, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5374
21 United States (Pennsylvania) United StatesPennsylvania2010 Alfalfa, Spring Barley, and Wheat pyroxsulam, thifensulfuron-methyl, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed7898
22 United States (Delaware) United StatesDelaware2012 Wheat thifensulfuron-methyl, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed5708
23 United States (Kentucky) United StatesKentucky2013 Wheat chlorsulfuron, flucarbazone-Na, thifensulfuron-methyl, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed7883
24 United States (California) United StatesCalifornia2022 Triticale, and Wheat mesosulfuron-methyl, pyroxsulam, and tribenuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
168Stellaria mediaCommon Chickweed24253
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