International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Polygonum persicaria)

Photosystem II- Serine 264 Binders (C1/5)

United States, Michigan
Ladysthumb (Polygonum persicaria) is a dicot weed in the Polygonaceae family.  In Michigan this weed first evolved resistance to Group C1/5 herbicides in 2001 and infests Blueberries.   Group C1/5 herbicides are known as Photosystem II- Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ).  Research has shown that these particular biotypes are resistant to atrazine, and simazine 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 May 12, 2003 )

Common NameLadysthumb
SpeciesPolygonum persicaria
GroupPhotosystem II- Serine 264 Binders (C1/5)
Herbicidesatrazine, and simazine
LocationUnited States, Michigan
Contributors - (Alphabetically)Steven Gower 
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Steven Gower
Mature ladysthumb seedheads were collected from a blueberry field in southwest Michigan suspected to be resistant to triazine herbicides. Herbicide resistance was evaluated using a greenhouse plant bioassay. Ladysthumb plants received a PRE application of simazine at 3.96 and 11.88 lbs. ai/A and a POST application of atrazine at 2 and 6 lbs. ai/A (1 and 3X standard field rate, respectively). Other treatments included sensitive and untreated controls. Ladysthumb completely survived applications of simazine and atrazine (1 and 3X rate) with no observed injury, when compared to sensitive and untreated controls. These results indicate that this particular ladysthumb biotype is highly resistant to triazine herbicides.

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Confirmation Tests

Greenhouse 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 Group C1/5 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

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 Ladysthumb from Michigan.
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Former Weed Science Diagnostician (Now with Monsanto)
Michigan State University
Diagnostic Services
578 Wilson Rd.
East Lansing, 48824, Michigan
United States
Email Steven Gower


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Michigan have been instrumental in providing you this information. Particular thanks is given to Steven Gower 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, prometryn, simazine, and terbutryn 12 Photosystem II- Serine 264 Binders (C1/5)
136Polygonum persicariaLadysthumb82
2 FranceFrance 1980 Corn (maize), and Cropland atrazine 17 Photosystem II- Serine 264 Binders (C1/5)
136Polygonum persicariaLadysthumb467
3 New ZealandNew Zealand 1980 Corn (maize) atrazine 30 Photosystem II- Serine 264 Binders (C1/5)
136Polygonum persicariaLadysthumb157
4 NorwayNorway 2009 Spring Barley, and Wheat tribenuron-methyl 31 ALS inhibitors (B/2)
136Polygonum persicariaLadysthumb10977
5 United States (Michigan) United StatesMichigan2001 Blueberries atrazine, and simazine 45 Photosystem II- Serine 264 Binders (C1/5)
136Polygonum persicariaLadysthumb5178
Literature about Similar Cases

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