(Capsella bursa-pastoris)

Photosystem II inhibitors (C1/5)

United States, Oregon
Shepherd's-purse (Capsella bursa-pastoris) is a dicot weed in the Brassicaceae family.  In Oregon this weed first evolved resistance to Group C1/5 herbicides in 2007 and infests Alfalfa.   Group C1/5 herbicides are known as Photosystem II inhibitors (Inhibition of photosynthesis at photosystem II).  Research has shown that these particular biotypes are resistant to hexazinone, and metribuzin and they may be cross-resistant to other Group C1/5 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 06, 2009 )

Common NameShepherd's-purse
SpeciesCapsella bursa-pastoris
GroupPhotosystem II inhibitors (C1/5)
Herbicideshexazinone, and metribuzin
LocationUnited States, Oregon
Contributors - (Alphabetically)Carol Mallory-Smith, and Alejandro Perez-Jones 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Shepherd's-purse biotype with this Shepherd's-purse 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 C1/5 resistant Shepherd's-purse indicate that the inheritance is determined by a one gene, cytoplasmic trait.  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 C1/5 resistant Shepherd's-purse from Oregon indicate that resistance is due to an altered target site.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
Relative Fitness

Triazine resistant weeds often exhibit a lower relative fitness when compared to susceptible biotypes.  The most common mutation conferring triazine resistance (Ser 264 to Gly mutation of the psbA gene) also causes a reduction in CO2 fixation, quantum yield, and seed and biomass production.  There is no record in this database referring specifically to fitness studies on Group C1/5 resistant Shepherd's-purse from Oregon.
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Oregon State University
Department of Crop And Soil Science
331B Crop Science Bldg
Corvallis, 97331, Oregon
United States
Email Carol Mallory-Smith
Web   : Web Site Link
Weed Research Specialist
Chemistry Technology
402 West State Farm Road
St. Louis, 63167, Missouri
United States
Email Alejandro Perez-Jones
Web   : Web Site Link


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 Carol Mallory-Smith, and Alejandro Perez-Jones for providing detailed information.
Herbicide Resistant Shepherd's-purse Globally
(Capsella bursa-pastoris)
Herbicide Resistant Shepherd's-purse Globally
(Capsella bursa-pastoris)
Drag a column header and drop it here to group by that column
Herbicide Resistant Shepherd's-purse Globally
(Capsella bursa-pastoris)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Saskatchewan) CanadaSaskatchewan2008 Wheat imazamox, imazethapyr, thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse5381
2 Canada (Alberta) CanadaAlberta2011 Wheat thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse5623
3 ChinaChina 2009 Winter wheat tribenuron-methyl 9 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse5502
4 DenmarkDenmark 2012 Spring Barley florasulam, and tribenuron-methyl 13 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse8910
5 IsraelIsrael 2000 Roadsides imazapyr 23 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse5465
6 NorwayNorway 2019 Wheat iodosulfuron-methyl-sodium 31 ALS inhibitors (B/2)
41Capsella bursa-pastorisShepherd's-purse18169
7 PolandPoland 1984 Orchards simazine 33 Photosystem II inhibitors (C1/5)
41Capsella bursa-pastorisShepherd's-purse166
8 United States (Oregon) United StatesOregon2007 Alfalfa hexazinone, and metribuzin 45 Photosystem II inhibitors (C1/5)
41Capsella bursa-pastorisShepherd's-purse5366
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.  Saturday, March 6, 2021 .  Available Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.