(Plantago lanceolata)

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

South Africa, Western Cape
Buckhorn Plantain (Plantago lanceolata) is a dicot weed in the Plantaginaceae family.  In South Africa this weed first evolved resistance to Group 9 (Legacy G) herbicides in 2003 and infests Grapes, and Orchards.   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 Aug 15, 2003 )

Common NameBuckhorn Plantain
SpeciesPlantago lanceolata
GroupInhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
LocationSouth Africa, Western Cape
Situation(s)Grapes, and Orchards
Contributors - (Alphabetically)Andrew Cairns 
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Andrew Cairns
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Glyphosate-resistant Plantago lanceolata in the Western Cape.

In May 2003 a sample of Plantago lanceolata seed, which had been harvested from plants from an area that had a history of poor control with glyphosate, was received from an Agro-Chemical company for resistance evaluation. This population of P. lanceolata was found to be growing in a vineyard in the Breede Valley (about 100km north east of Cape Town). The seed was germinated in an incubator and the seedlings planted out in pots. Seedlings from two other P. lanceolata populations, one from an undisturbed area (Rondebosch Common, Cape Town) and the other from a cultivated land (Welgevallen Experimental Farm, Stellenbosch), were planted as controls. Six weeks after planting out, when the plants were in the 4 - 8 leaf stage, the three populations were subjected to a range of glyphosate dosage rates viz. 0.36, 0.72, 1.08, 1.44, 2.16, 2.88, and 3.60 kg a.e. glyphosate ha-1. The Breede Valley population was also subjected to higher range of dosage rates viz. 4.32, 5.04, 5.76, 6.48, 7.20 kg a.e. glyphosate ha-1. Four replicates per treatment were used.

No treatment gave acceptable control of the Breede Valley population (Table 1). Dose response between 4.32 and 7.20 kg glyphosate ha-1 was flat and differences in the control levels within this dosage range were probably due to natural variability in the population. The level of control achieved of the Welgevallen and Rondebosch populations of P. lanceolata was acceptable. This trial was rated 56 days after treatment.

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Andrew Cairns

Table 1. Dose response of three Western Cape populations of Plantago lanceolata to glyphosate.

Treatment  Control (%)
(kg a.e. glyphosate ha-1)  Population
  Breede Valley Ronde-bosch Welge-vallen
0 0 0
0.72 0 82 63
1.44 0 100 94
2.16 0 100 100
2.88 18 100 100
3.60 7 100 100
4.32  74 nt* nt
5.04 50 nt nt
5.76 89 nt nt
6.48 56 nt nt
7.20 62 nt nt

*nt = not tested

Work is in progress to map the extent of glyphosate-resistant populations of P. lanceolata in the Western Cape, and to identify cost effective control strategies.

A.L.P. Cairns
Department of Agronomy
University of Stellenbosch

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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 9 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 9 (Legacy G) resistant Buckhorn Plantain from South Africa please update the database.
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University Of Stellenbosch
Department Of Agronomy
Land Resources& Environmental Sci Dept
334 Leon Johnson Hall,
Matieland, 7602
South Africa
Email Andrew Cairns


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in South Africa have been instrumental in providing you this information. Particular thanks is given to Andrew Cairns 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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