International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP O/4 RESISTANT CANADA THISTLE
(Cirsium arvense)


Synthetic Auxins (O/4)

Sweden
INTRODUCTION CANADA THISTLE
Canada thistle (Cirsium arvense) is a dicot weed in the Asteraceae family.  In Sweden this weed first evolved resistance to Group O/4 herbicides in 1979 and infests Cropland.   Group O/4 herbicides are known as Synthetic Auxins (Synthetic auxins (action like indoleacetic acid)).  Research has shown that these particular biotypes are resistant to MCPA and they may be cross-resistant to other Group O/4 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 Sep 15, 2000 )

Common NameCanada thistle
SpeciesCirsium arvense
GroupSynthetic Auxins (O/4)
HerbicidesMCPA
LocationSweden
Year1979
Situation(s)Cropland
Contributors - (Alphabetically) 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Fogelfors, H. 1979. "Changes in the Flora of Farmland" Swed. Univ. Agric. Sci. Dept, Ecol. Environ. Res. Rep. No. 5, Uppsala. pp 66.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Canada thistle biotype with this Canada 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.
 
Genetics

Genetic studies on Group O/4 resistant Canada 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 O/4 resistant Canada thistle from Sweden please update the database.
 
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CONTRIBUTING WEED SCIENTISTS


ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Sweden have been instrumental in providing you this information. 
Herbicide Resistant Canada thistle Globally
(Cirsium arvense)
Herbicide Resistant Canada thistle Globally
(Cirsium arvense)
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Herbicide Resistant Canada thistle Globally
(Cirsium arvense)
#CountryFirstYearSituationActive IngredientsSite of Action
1 HungaryHungary 1985 Pastures 2,4-D, and MCPA 20 Synthetic Auxins (O/4)
55Cirsium arvenseCanada thistle306
2 SwedenSweden 1979 Cropland MCPA 40 Synthetic Auxins (O/4)
55Cirsium arvenseCanada thistle395
Literature about Similar Cases

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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Wednesday, July 17, 2019 .  Available  www.weedscience.org
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