International Survey of Herbicide-Resistant Weeds

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GROUP B/2 RESISTANT RICEFIELD BULRUSH
(Schoenoplectus mucronatus (=Scirpus mucronatus))


ALS inhibitors (B/2)

Italy
INTRODUCTION RICEFIELD BULRUSH
Ricefield Bulrush (Schoenoplectus mucronatus (=Scirpus mucronatus)) is a monocot weed in the Cyperaceae family.  In Italy this weed first evolved resistance to Group B/2 herbicides in 1995 and infests Rice.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)).  Research has shown that these particular biotypes are resistant to azimsulfuron, bensulfuron-methyl, cinosulfuron, and ethoxysulfuron and they may be cross-resistant to other Group B/2 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 May 08, 2014 )

Common NameRicefield Bulrush
SpeciesSchoenoplectus mucronatus (=Scirpus mucronatus)
GroupALS inhibitors (B/2)
Herbicidesazimsulfuron, bensulfuron-methyl, cinosulfuron, and ethoxysulfuron
LocationItaly
Year1995
Situation(s)Rice
Contributors - (Alphabetically)Maurizio Sattin 
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Maurizio Sattin
Novara, Pavia, Vercelli, Milano, Biella

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GENERAL

Maurizio Sattin
There is a generalised cross resistance among the sulfonylureas (Azimsulfuron, Bensulfuron- methyl, Cinosulfuron, Ethoxysulfuron) as well as to the triazolopyrimidine (metosulam), but the level of resistance which appears to be very high for the sulfonylurea (the ratios between the GR50 of the resistant and susceptible biotypes are higher than 650) it is, in general, more variable for Metosulam (GR50 varies between 88 to 514). A few populations show very high level of resistance to both sulfonylureas and triazolopyrimidine:. Although there is as yet no direct experimental proof, the available information suggests that the resistance mechanism could be a target-site. It is now estimated that between 10,000 and 15,000 ha are affected. Most resistant populations come from Novara Province and were selected by bensulfuron -methyl. The field histories suggest that resistance developed in a paddy rice monoculture system after at least three-four years using an ALS inhibitor alone for controlling these two species. Generally, resistance has not developed where the weed control strategy is devised in relation to the presence of red rice.

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GENERAL

Roberto Busi
Schoenoplectus mucronatus (L.) Palla and Cyperus difformis L. accessions resistant to ALS-inhibitors in Italian rice fields.

Vidotto, F; Busi, R; Ferrero, A. Dipartimento di Agronomia, Selvicoltura e Gestione del Territorio. Grugliasco, Italy.

Sulfonylureas and other ALS-inhibitor herbicides have been used in Italian paddy fields for more than 10 years. Since 1995, lack of control has been reported for Alisma plantago-aquatica L. and Schoenoplectus mucronatus (L.) Palla. Starting from 1999, insufficient efficacy of ALS-inhibitors herbicides have been reported also against Cyperus difformis L.  A dose-response study has been carried out in the greenhouse to estimate the sensitivity of different S. mucronatus and C. difformis accessions to two bensulfuron-methyl and cinosulfuron.  Two S. mucronatus (RS1 and RS2) and one C. difformis (RC1)accessions that escaped field treatments were sprayed either with bensulfuron-methyl or cinosulfuron at 8 doses, from 0 to 4x the recommended field rate (100 g a.i.ha-1 and 80 g a.i.ha-1 for bensulfuron and cinosulfuron, respectively). Two additional accessions were also included as sensitive references (SS and SC, for S. mucronatus and C. difformis, respectively). Seeds of both species were placed on 36 cm2 pots filled with commercial potting substrate. Prior to seeding, S. mucronatus seeds were scarified with sulphuric acid for 5’. Treatments were applied at 4-leaf stage. Aboveground fresh weight per pot was determined 15-20 days after spraying.   In S. mucronatus, the rate determining 50% of growth reduction (GR50) referred to bensulfuron-methyl and cinosulfuron was more than 1,000 and 100 times higher, respectively, than that of SS, both in RS1 and RS2. In C. difformis, the GR50 of RC1 referred to bensulfuron-methyl was higher than 4x. In the case of cinosulfuron, GR50 of RC1 was more than 700 times higher than that of SC.  The accessions of both species show a variable degree of resistance both to bensulfuron-methyl and cinosulfuron, which are widely used in Italian rice fields. Further investigations are needed to understand the mechanism of resistance.

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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Ricefield Bulrush biotype with this Ricefield Bulrush 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 Group B/2 resistant Ricefield Bulrush 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 B/2 resistant Ricefield Bulrush from Italy please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

MAURIZIO SATTIN
Senior Weed Scientist
Italian National Research Council (cnr)
IBAF - Weed Science Unit
Viale dell'Università 16
Legnaro, 35020, Padova
Italy
Email Maurizio Sattin

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Italy have been instrumental in providing you this information. Particular thanks is given to Maurizio Sattin for providing detailed information.
Herbicide Resistant Ricefield Bulrush Globally
(Schoenoplectus mucronatus (=Scirpus mucronatus))
Herbicide Resistant Ricefield Bulrush Globally
(Schoenoplectus mucronatus (=Scirpus mucronatus))
Drag a column header and drop it here to group by that column
Herbicide Resistant Ricefield Bulrush Globally
(Schoenoplectus mucronatus (=Scirpus mucronatus))
#CountryFirstYearSituationActive IngredientsSite of Action
1 ChileChile 2005 Rice bensulfuron-methyl, bispyribac-sodium, cyclosulfamuron, ethoxysulfuron, imazamox, and pyrazosulfuron-ethyl 8 ALS inhibitors (B/2)
182Schoenoplectus mucronatus (=Scirpus mucronatus)Ricefield Bulrush5396
2 ItalyItaly 1995 Rice azimsulfuron, bensulfuron-methyl, cinosulfuron, and ethoxysulfuron 24 ALS inhibitors (B/2)
182Schoenoplectus mucronatus (=Scirpus mucronatus)Ricefield Bulrush1129
3 United States (California) United StatesCalifornia1997 Rice bensulfuron-methyl 45 ALS inhibitors (B/2)
182Schoenoplectus mucronatus (=Scirpus mucronatus)Ricefield Bulrush1099
4 United States (California) United StatesCalifornia2014 Rice propanil 45 PSII inhibitor (Ureas and amides) (C2/7)
182Schoenoplectus mucronatus (=Scirpus mucronatus)Ricefield Bulrush9924
Literature about Similar Cases

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