International Survey of Herbicide-Resistant Weeds

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HRAC GROUP 5 (LEGACY C1 C2) RESISTANT SMALLFLOWER UMBRELLA SEDGE
(Cyperus difformis)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

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 5 (Legacy C1 C2) herbicides in 2013 and infests Rice.   Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ).  Research has shown that these particular biotypes are resistant to propanil and they may be cross-resistant to other Group 5 (Legacy C1 C2) 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 Jul 30, 2013 )

Common NameSmallflower Umbrella Sedge
SpeciesCyperus difformis
GroupPSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicidespropanil
LocationUnited States, California
Year2013
Situation(s)Rice
Contributors - (Alphabetically)Albert Fischer, and Rafael Pedroso 
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NOTES ABOUT THIS BIOTYPE

MECHANISM

Rafael Pedroso
Carbaryl and malathion reduced the resistance level (ED20) of the R population PP, suggesting a contribution of enhanced metabolism towards the mechanism of resistance. The ED20 was more reduced by the addition of carbaryl than by malathion, thus the stronger resistance mitigation by carbaryl suggests enhanced aryl-acylamidase activity could be more relevant than P450 metabolism as a mechanism of resistance3,4. The S population (HR) had much lower ED20 and ED50 values than PP (R) in all cases

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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 5 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

Studies on the mechanism of resistance of Group 5 (Legacy C1 C2) resistant Smallflower Umbrella Sedge from California indicate that resistance is due to enhanced metabolism.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
 
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 5 (Legacy C1 C2) resistant Smallflower Umbrella Sedge from California please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

ALBERT FISCHER
Professor
University Of California
Department of Plant Sciences
Weed Ecophysiology
Mail Stop #4 279/279A Robbins Hall
Davis, 95616, California
United States
Email Albert Fischer
Web   : Web Site Link
RAFAEL PEDROSO
PhD Student and Graduate Student Researcher
University of California at Davis
Plant Sciences
One Shields Avenue
Davis, 95616, California
United States
Email Rafael Pedroso
Web   : Web Site Link

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 Albert Fischer, and Rafael Pedroso 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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