International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Polygonum persicaria)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Ladysthumb (Polygonum persicaria) is a dicot weed in the Polygonaceae family.  In Norway this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2009 and infests Spring Barley, 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 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.

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 09, 2015 )

Common NameLadysthumb
SpeciesPolygonum persicaria
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Situation(s)Spring Barley, and Wheat
Contributors - (Alphabetically)Jan Netland 
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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Ladysthumb biotype with this Ladysthumb 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 HRAC Group 2 resistant Ladysthumb 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 Ladysthumb from Norway please update the database.
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The Norwegian Crop Research Institute
Plant Protection Centre
Department Of Herbology
Exotic & Invasive Weed Research
One Shields Ave, Mail Stop 4
Fellesbygget, N-1432, ÅS
Email Jan Netland


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Norway have been instrumental in providing you this information. Particular thanks is given to Jan Netland for providing detailed information.
Herbicide Resistant Ladysthumb Globally
(Polygonum persicaria)
Herbicide Resistant Ladysthumb Globally
(Polygonum persicaria)
Drag a column header and drop it here to group by that column
Herbicide Resistant Ladysthumb Globally
(Polygonum persicaria)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Czech RepublicCzech Republic 1989 Railways atrazine, cyanazine, lenacil, prometryne, simazine, and terbutryne 12 PSII inhibitors - Serine 264 Binders (C1 C2/5)
136Polygonum persicariaLadysthumb82
2 FranceFrance 1980 Corn (maize), and Cropland atrazine 17 PSII inhibitors - Serine 264 Binders (C1 C2/5)
136Polygonum persicariaLadysthumb467
3 New ZealandNew Zealand 1980 Corn (maize) atrazine 30 PSII inhibitors - Serine 264 Binders (C1 C2/5)
136Polygonum persicariaLadysthumb157
4 NorwayNorway 2009 Spring Barley, and Wheat tribenuron-methyl 31 Inhibition of Acetolactate Synthase (B/2)
136Polygonum persicariaLadysthumb10977
5 United States (Michigan) United StatesMichigan2001 Blueberries atrazine, and simazine 45 PSII inhibitors - Serine 264 Binders (C1 C2/5)
136Polygonum persicariaLadysthumb5178
Literature about Similar Cases

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