International Survey of Herbicide-Resistant Weeds

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(Plantago lanceolata)

Auxin Mimics HRAC Group 4 (Legacy O)

United States, Indiana
Buckhorn Plantain (Plantago lanceolata) is a dicot weed in the Plantaginaceae family.  In Indiana this weed first evolved resistance to Group 4 (Legacy O) herbicides in 2016 and infests Turf.   Group 4 (Legacy O) herbicides are known as Auxin Mimics (Auxin Mimics ).  Research has shown that these particular biotypes are resistant to 2,4-D and they may be cross-resistant to other Group 4 (Legacy O) 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 Mar 08, 2018 )

Common NameBuckhorn Plantain
SpeciesPlantago lanceolata
GroupAuxin Mimics HRAC Group 4 (Legacy O)
LocationUnited States, Indiana
Contributors - (Alphabetically)Aaron Patton 
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Aaron Patton

Patton AJ, Weisenberger DV, Schortgen GP (2018) 2,4-D–Resistant Buckhorn Plantain (Plantago lanceolata) in Managed Turf. Weed Technol. doi: 10.1017/ wet.2017.98


A population of buckhorn plantain with suspected resistance to 2,4-D was identified in central Indiana following 30 yr of 2,4-D–containing herbicide applications. Our objectives were to (1) confirm and quantify the level of herbicide resistance in the buckhorn plantain population using dose–response experiments and (2) find alternative herbicides that could be used to control this population. Greenhouse experiments were conducted to quantify the dose–response of resistant (R) and susceptible (S) biotypes of buckhorn plantain to both 2,4-D and triclopyr, two synthetic auxin herbicides from different chemical families. The R biotype was ≥6.2 times less sensitive to 2,4-D than the S biotype. The efficacy of triclopyr was similar on both the R and S biotypes of buckhorn plantain, suggesting the absence of cross-resistance to this herbicide. This is the first report of 2,4-D resistance in buckhorn plantain and the first report of 2,4-D resistance in turf. The resistance mechanism was limited to within a chemical family (phenoxycarboxylic acid) and did not occur across all WSSA Group 4 synthetic auxin herbicides, as the pyridinecarboxylic acid herbicides clopyralid and triclopyr and the arylpicolinate herbicide halauxifen-methyl provided control in our experiments.

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Confirmation Tests

Greenhouse trials comparing a known susceptible Buckhorn Plantain biotype with this Buckhorn Plantain 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 4 resistant Buckhorn Plantain 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 4 (Legacy O) resistant Buckhorn Plantain from Indiana please update the database.
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Purdue University
Horticulture and Landscape Architecture
625 Agriculture Mall Dr
Horticulture Building
West Lafayette, 47907-2010, Indiana
United States
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The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Indiana have been instrumental in providing you this information. Particular thanks is given to Aaron Patton for providing detailed information.
Herbicide Resistant Buckhorn Plantain Globally
(Plantago lanceolata)
Herbicide Resistant Buckhorn Plantain Globally
(Plantago lanceolata)
Drag a column header and drop it here to group by that column
Herbicide Resistant Buckhorn Plantain Globally
(Plantago lanceolata)
#CountryFirstYearSituationActive IngredientsSite of Action
1 South AfricaSouth Africa 2003 Grapes, and Orchards glyphosate 37 Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)
220Plantago lanceolataBuckhorn Plantain5196
2 South AfricaSouth Africa 2022 Grapes glyphosate, and paraquat 37 Multiple Resistance: 2 Sites of Action
PS I Electron Diversion ( HRAC Group 22 (Legacy D)
Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)
220Plantago lanceolataBuckhorn Plantain27276
3 United States (Indiana) United StatesIndiana2016 Turf 2,4-D 45 Auxin Mimics ( HRAC Group 4 (Legacy O)
220Plantago lanceolataBuckhorn Plantain17133
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