(Stellaria media)

ALS inhibitors (B/2)

United States, Pennsylvania
Common Chickweed (Stellaria media) is a dicot weed in the Caryophyllaceae family.  In Pennsylvania this weed first evolved resistance to Group B/2 herbicides in 2010 and infests Alfalfa, Spring Barley, and Wheat.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to pyroxsulam, thifensulfuron-methyl, and tribenuron-methyl and they may be cross-resistant to other Group B/2 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.

If we do not have a picture for this weed, or you can provide a better picture (scan, digital camera etc) please please e-mail it to us.

QUIK STATS (last updated Mar 31, 2014 )

Common NameCommon Chickweed
SpeciesStellaria media
GroupALS inhibitors (B/2)
Herbicidespyroxsulam, thifensulfuron-methyl, and tribenuron-methyl
LocationUnited States, Pennsylvania
Situation(s)Alfalfa, Spring Barley, and Wheat
Contributors - (Alphabetically)William Curran 
Edit this Case  |  Add New Case of Resistance  |  Add Note


Confirmation Tests

Field 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.

Genetic studies on Group B/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 B/2 resistant Common Chickweed from Pennsylvania please update the database.
Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  


Professor of Weed Science
Pennsylvania State University
Department of Plant Science
423 Agricultural Sciences and Industries Building
University Park, 16802, Pennsylvania
United States
Email William Curran
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Pennsylvania have been instrumental in providing you this information. Particular thanks is given to William Curran 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 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed10959
2 Canada (Alberta) CanadaAlberta1988 Cereals, and Wheat chlorsulfuron, ethametsulfuron-methyl, imazamethabenz-methyl, metsulfuron-methyl, sulfometuron-methyl, and thifensulfuron-methyl 7 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed481
3 Canada (Saskatchewan) CanadaSaskatchewan2005 Spring Barley, and Wheat thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5322
4 Canada (Manitoba) CanadaManitoba2008 Peas thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5630
5 ChinaChina 2010 Winter wheat fluroxypyr, and MCPA 9 Auxin Mimics (O/4)
168Stellaria mediaCommon Chickweed5658
6 DenmarkDenmark 1991 Spring Barley, and Wheat chlorsulfuron, florasulam, iodosulfuron-methyl-sodium, and tribenuron-methyl 13 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed86
7 FinlandFinland 2013 Spring Barley tribenuron-methyl 139 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed9946
8 FranceFrance 2012 Wheat florasulam, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, and thifensulfuron-methyl 17 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5688
9 GermanyGermany 1978 Corn (maize) atrazine 18 Photosystem II- Serine 264 Binders (C1/5)
168Stellaria mediaCommon Chickweed435
10 GermanyGermany 2011 Rapeseed, Spring Barley, and Wheat amidosulfuron, florasulam, imazamox, iodosulfuron-methyl-sodium, mesosulfuron-methyl, nicosulfuron, pyroxsulam, thifensulfuron-methyl, tribenuron-methyl, triflusulfuron-methyl, and tritosulfuron 18 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed6744
11 IrelandIreland 1996 Cereals metsulfuron-methyl 81 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5089
12 LatviaLatvia 2016 Winter wheat amidosulfuron 174 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed15068
13 New ZealandNew Zealand 1995 Cereals chlorsulfuron 30 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed161
14 NorwayNorway 2002 Cereals iodosulfuron-methyl-sodium, metsulfuron-methyl, and tribenuron-methyl 31 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5165
15 South AfricaSouth Africa 2002 Cereals chlorsulfuron, metsulfuron-methyl, thifensulfuron-methyl, and triasulfuron 37 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5193
16 SwedenSweden 1995 Spring Barley, Spring wheat, and Winter wheat chlorsulfuron, florasulam, and tribenuron-methyl 40 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed510
17 United KingdomUnited Kingdom 1985 Cereals, and Wheat mecoprop 44 Auxin Mimics (O/4)
168Stellaria mediaCommon Chickweed358
18 United KingdomUnited Kingdom 2000 Cereals florasulam, and metsulfuron-methyl 44 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5088
19 United States (Virginia) United StatesVirginia2008 Wheat thifensulfuron-methyl 45 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5373
20 United States (Maryland) United StatesMaryland2009 Wheat chlorsulfuron, mesosulfuron-methyl, thifensulfuron-methyl, and tribenuron-methyl 45 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5374
21 United States (Pennsylvania) United StatesPennsylvania2010 Alfalfa, Spring Barley, and Wheat pyroxsulam, thifensulfuron-methyl, and tribenuron-methyl 45 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed7898
22 United States (Delaware) United StatesDelaware2012 Wheat thifensulfuron-methyl, and tribenuron-methyl 45 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed5708
23 United States (Kentucky) United StatesKentucky2013 Wheat chlorsulfuron, flucarbazone-sodium, thifensulfuron-methyl, and tribenuron-methyl 45 ALS inhibitors (B/2)
168Stellaria mediaCommon Chickweed7883
Literature about Similar Cases

Page size:
Page: of 10
Items 1 to 5 of 46

Page size:
Page: of 10
Items 1 to 5 of 46

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.  Tuesday, April 20, 2021 .  Available Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.