International Survey of Herbicide-Resistant Weeds

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(Bromus catharticus)

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)

Argentina, Buenos Aires Province
Rescuegrass (Bromus catharticus) is a monocot weed in the Poaceae family.  In Argentina this weed first evolved resistance to Group 9 (Legacy G) herbicides in 2017 and infests Fallow, Wheat, and Winter barley.   Group 9 (Legacy G) herbicides are known as Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (Inhibition of EPSP synthase).  Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group 9 (Legacy G) 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 02, 2018 )

Common NameRescuegrass
SpeciesBromus catharticus
GroupInhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
LocationArgentina, Buenos Aires Province
Situation(s)Fallow, Wheat, and Winter barley
Contributors - (Alphabetically)Marcos Yanniccari 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Rescuegrass biotype with this Rescuegrass 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 9 resistant Rescuegrass 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 9 (Legacy G) resistant Rescuegrass from Argentina please update the database.
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Chacra Experimental Integrada Barrow
RN 3 km 487 cc 50
Tres Arroyos, 7500, Buenos Aires
Email Marcos Yanniccari


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Argentina have been instrumental in providing you this information. Particular thanks is given to Marcos Yanniccari for providing detailed information.
Herbicide Resistant Rescuegrass Globally
(Bromus catharticus)
Herbicide Resistant Rescuegrass Globally
(Bromus catharticus)
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Herbicide Resistant Rescuegrass Globally
(Bromus catharticus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ArgentinaArgentina 2017 Fallow, Wheat, and Winter barley glyphosate 48 Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9)
338Bromus catharticusRescuegrass17144
Literature about Similar Cases

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