INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

MULTIPLE RESISTANT SMALLFLOWER UMBRELLA SEDGE
(Cyperus difformis)


Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
PSII inhibitors - Histidine 215 Binders HRAC Group 6 (Legacy C3)

Portugal, Alentejo
INTRODUCTION SMALLFLOWER UMBRELLA SEDGE
Smallflower Umbrella Sedge (Cyperus difformis) is a monocot weed in the Cyperaceae family.  In Portugal this weed first evolved multiple resistance (to 2 herbicide sites of action) in 2023 and infests Rice.  Multiple resistance has evolved to herbicides in the Groups 2 (Legacy B), and PSII inhibitors - Histidine 215 Binders HRAC Group 6 (Legacy C3).  These particular biotypes are known to have resistance to bentazon, and penoxsulam and they may be cross-resistant to other herbicides in the Groups 2 (Legacy B), and PSII inhibitors - Histidine 215 Binders HRAC Group 6 (Legacy C3).

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 Jun 06, 2024 )

Common NameSmallflower Umbrella Sedge
SpeciesCyperus difformis
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

PSII inhibitors - Histidine 215 Binders HRAC Group 6 (Legacy C3)
Herbicidesbentazon, and penoxsulam
LocationPortugal, Alentejo
Year2023
Situation(s)Rice
Contributors - (Alphabetically)Isabel Calha 
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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse 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, 6 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 multiple resistant Smallflower Umbrella Sedge from Portugal indicate that resistance is due to an altered target site.  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 multiple resistant Smallflower Umbrella Sedge from Portugal please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

ISABEL CALHA
Instituto Nacional De Recursos Biológicos, Ip (inrb I.p. )
Laboratório Nacional De Investigação Agrária (linia)
Unidade De Investigação De Protecção De Plantas (uipp)
Dept of Agronomy& Plant Genetics
411 Borlaug Hall, 1991 Upper Buford Circle
Oeiras, 2784-505
Portugal
Email Isabel Calha

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Portugal have been instrumental in providing you this information. Particular thanks is given to Isabel Calha 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 PortugalPortugal 2023 Rice bentazon, and penoxsulam 34 Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Histidine 215 Binders ( HRAC Group 6 (Legacy C3)
71Cyperus difformisSmallflower Umbrella Sedge28270
7 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
8 SpainSpain 2000 Rice bensulfuron-methyl, and penoxsulam 38 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
71Cyperus difformisSmallflower Umbrella Sedge5140
9 TurkeyTurkey 2010 Rice azimsulfuron, bensulfuron-methyl, bispyribac-sodium, and penoxsulam 71 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
71Cyperus difformisSmallflower Umbrella Sedge5532
10 United States (California) United StatesCalifornia1993 Rice bensulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
71Cyperus difformisSmallflower Umbrella Sedge391
11 United States (Arkansas) United StatesArkansas2010 Rice halosulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
71Cyperus difformisSmallflower Umbrella Sedge5562
12 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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Heap, I.  The International Herbicide-Resistant Weed Database.  Online.  Thursday, July 18, 2024 .  Available  www.weedscience.org Copyright © 1993- 2024 WeedScience.org All rights reserved. Fair use of this material is encouraged. Proper citation is requested.