International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
HRAC GROUP 2 (LEGACY B) RESISTANT SMALLFLOWER UMBRELLA SEDGE
(Cyperus difformis)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, California
INTRODUCTION SMALLFLOWER UMBRELLA SEDGE
Smallflower Umbrella Sedge (Cyperus difformis) is a monocot weed in the Cyperaceae family.  In California this weed first evolved resistance to Group 2 (Legacy B) herbicides in 1993 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 bensulfuron-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.

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QUIK STATS (last updated Sep 15, 2000 )

Common NameSmallflower Umbrella Sedge
SpeciesCyperus difformis
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesbensulfuron-methyl
LocationUnited States, California
Year1993
Situation(s)Rice
Contributors - (Alphabetically)Michael Carriere 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Michael Carriere
Resistance of California Arrowhead and Smallflower Umbrella Sedge to Sulfonylurea Herbicides. T. Pappas-Fader, J. F. Cook, T. Butler, P.J. Lana, E.I. DuPont de Nemours and Company, Stine-Haskell Research Center, Newark, DE 19714 and J.Hare, Pest Control Advisor, The John Taylor Fertilizer Company, 900 N. George Washington St. Yuba City, CA 95993. In Proceedings of the Western Weed Science Society (Newark, CA: Western Society of Weed Science, 1993), p. 76.

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GENERAL

Michael Carriere
Remains susceptible to thiobencarb, propanil, and carfentrazone.

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ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Smallflower Umbrella Sedge biotype with this Smallflower Umbrella Sedge 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 HRAC Group 2 resistant Smallflower Umbrella Sedge 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 Smallflower Umbrella Sedge from California please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

MICHAEL CARRIERE
Strawberry Licensing Program
University Of California
UC Davis Innovation Access
1850 Research Park Drive
Suite 100
Davis, 95618, California
United States
Email Michael Carriere

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in California have been instrumental in providing you this information. Particular thanks is given to Michael Carriere for providing detailed information.
Herbicide Resistant Smallflower Umbrella Sedge Globally
(Cyperus difformis)
Herbicide Resistant Smallflower Umbrella Sedge Globally
(Cyperus difformis)
Drag a column header and drop it here to group by that column
Herbicide Resistant Smallflower Umbrella Sedge Globally
(Cyperus difformis)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Australia (New South Wales ) AustraliaNew South Wales 1994 Rice bensulfuron-methyl 1 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge6
2 BrazilBrazil 2000 Rice cyclosulfamuron, and pyrazosulfuron-ethyl 5 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge5118
3 GreeceGreece 2009 Rice azimsulfuron, and halosulfuron-methyl 19 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge13051
4 IndiaIndia 2017 Rice bispyribac-sodium 21 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge23236
5 ItalyItaly 1999 Rice azimsulfuron, bensulfuron-methyl, and cinosulfuron 24 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge5155
6 South KoreaSouth Korea 2002 Rice azimsulfuron, bensulfuron-methyl, cinosulfuron, cyclosulfamuron, ethoxysulfuron, halosulfuron-methyl, imazosulfuron, and pyrazosulfuron-ethyl 27 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge152
7 SpainSpain 2000 Rice bensulfuron-methyl, and penoxsulam 38 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge5140
8 TurkeyTurkey 2010 Rice azimsulfuron, bensulfuron-methyl, bispyribac-sodium, and penoxsulam 71 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge5532
9 United States (California) United StatesCalifornia1993 Rice bensulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge391
10 United States (Arkansas) United StatesArkansas2010 Rice halosulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		71Cyperus difformisSmallflower Umbrella Sedge5562
11 United States (California) United StatesCalifornia2013 Rice propanil 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
 		71Cyperus difformisSmallflower Umbrella Sedge6739
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