International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Cyperus esculentus)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, Arkansas
Yellow Nutsedge (Cyperus esculentus) is a monocot weed in the Cyperaceae family.  In Arkansas this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2013 and infests Rice.   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 halosulfuron-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 Aug 03, 2016 )

Common NameYellow Nutsedge
SpeciesCyperus esculentus
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
LocationUnited States, Arkansas
Contributors - (Alphabetically)Jason Norsworthy, and Parsa Tehranchian 
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Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Yellow Nutsedge biotype with this Yellow Nutsedge 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 Yellow Nutsedge 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 Yellow Nutsedge from Arkansas please update the database.
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University Of Arkansas
Department Of Crop
Soil, And Environmental Sciences
1366 West Altheimer Drive
Williams Hall
Fayetteville, 72704, Arkansas
United States
Email Jason Norsworthy
Web   : Web Site Link
Postdoctoral Research Fellow
University of California
Plant Sciences
Department of Plant Sciences
Davis, 95616-8780, California
United States
Email Parsa Tehranchian
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Arkansas have been instrumental in providing you this information. Particular thanks is given to Jason Norsworthy, and Parsa Tehranchian for providing detailed information.
Herbicide Resistant Yellow Nutsedge Globally
(Cyperus esculentus)
Herbicide Resistant Yellow Nutsedge Globally
(Cyperus esculentus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Yellow Nutsedge Globally
(Cyperus esculentus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ItalyItaly 2017 Rice azimsulfuron, and halosulfuron-methyl 24 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
290Cyperus esculentusYellow Nutsedge24256
2 United States (Arkansas) United StatesArkansas2013 Rice halosulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
290Cyperus esculentusYellow Nutsedge6752
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