International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Rumex acetosella)

Photosystem II inhibitors (C1/5)

Canada, Nova Scotia
Sheep Sorrel (Rumex acetosella) is a dicot weed in the Polygonaceae family.  In Nova Scotia this weed first evolved resistance to Group C1/5 herbicides in 2011 and infests Blueberries.   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 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.

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 Jan 27, 2016 )

Common NameSheep Sorrel
SpeciesRumex acetosella
GroupPhotosystem II inhibitors (C1/5)
LocationCanada, Nova Scotia
Contributors - (Alphabetically)Francois Tardif 
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Francois Tardif
Hexazinone Resistance in Red Sorrel (Rumex acetosella)
Author(s): Zhenyi Li, Nathan Boyd, Nancy McLean, and Katherine Rutherford
Source: Weed Science, 62(3):532-537.
Zhenyi Li was the M Sc student and Nathan Boyd the supervisor.
Seed was collected at four sites in Nova Scotia in 2011

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Sheep Sorrel biotype with this Sheep Sorrel 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 Sheep Sorrel 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

Studies on the mechanism of resistance of Group C1/5 resistant Sheep Sorrel from Nova Scotia 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 Sheep Sorrel from Nova Scotia.
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Associate Professor
University Of Guelph
Department Of Plant Agriculture
2055 Radatz Ave
Guelph, N1G 2W1, Ontario
Email Francois Tardif
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Nova Scotia have been instrumental in providing you this information. Particular thanks is given to Francois Tardif for providing detailed information.
Herbicide Resistant Sheep Sorrel Globally
(Rumex acetosella)
Herbicide Resistant Sheep Sorrel Globally
(Rumex acetosella)
Drag a column header and drop it here to group by that column
Herbicide Resistant Sheep Sorrel Globally
(Rumex acetosella)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Nova Scotia) CanadaNova Scotia2011 Blueberries hexazinone 7 Photosystem II inhibitors (C1/5)
337Rumex acetosellaSheep Sorrel17122
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