International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
HRAC GROUP 2 (LEGACY B) RESISTANT ROUGHSTALK BLUEGRASS
(Poa trivialis)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Ireland, Meath County
INTRODUCTION ROUGHSTALK BLUEGRASS
Roughstalk Bluegrass (Poa trivialis) is a monocot weed in the Poaceae family.  In Ireland this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2023 and infests Wheat.   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 iodosulfuron-methyl-Na, mesosulfuron-methyl, and propoxycarbazone-Na 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 Jun 05, 2025 )

Common NameRoughstalk Bluegrass
SpeciesPoa trivialis
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesiodosulfuron-methyl-Na, mesosulfuron-methyl, and propoxycarbazone-Na
LocationIreland, Meath County
Year2023
Situation(s)Wheat
Contributors - (Alphabetically)Vijaya Bhaskar A.V. 
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Roughstalk Bluegrass biotype with this Roughstalk Bluegrass 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 Roughstalk Bluegrass 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 Roughstalk Bluegrass from Ireland please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

VIJAYA BHASKAR A.V.
Researcher
Crop Research Centre Oak Park, Teagasc, Carlow R93 XE12, Ireland
Crop Science
Crop Research Centre Oak Park
Teagasc, Carlow R93 XE12, Ireland
Carlow, R93 XE12, Carlow
Ireland
Email Vijaya Bhaskar A.V.
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ireland have been instrumental in providing you this information. Particular thanks is given to Vijaya Bhaskar A.V. for providing detailed information.
Herbicide Resistant Roughstalk Bluegrass Globally
(Poa trivialis)
Herbicide Resistant Roughstalk Bluegrass Globally
(Poa trivialis)
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Herbicide Resistant Roughstalk Bluegrass Globally
(Poa trivialis)
#CountryFirstYearSituationActive IngredientsSite of Action
1 FranceFrance 2012 Wheat iodosulfuron-methyl-Na, and mesosulfuron-methyl 17 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		350Poa trivialisRoughstalk Bluegrass18179
2 IrelandIreland 2023 Wheat iodosulfuron-methyl-Na, mesosulfuron-methyl, and propoxycarbazone-Na 81 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
 		350Poa trivialisRoughstalk Bluegrass31279
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Saturday, June 7, 2025 .  Available  www.weedscience.org
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