International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Eriochloa punctata)

Inhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)

Bolivia, Santa Cruz
Pasto Amargo (Eriochloa punctata) is a monocot weed in the Poaceae family.  In Bolivia this weed first evolved resistance to Group 1 (Legacy A) herbicides in 1997 and infests Soybean.   Group 1 (Legacy A) herbicides are known as Inhibition of Acetyl CoA Carboxylase (Inhibition of Acetyl CoA Carboxylase ).  Research has shown that these particular biotypes are resistant to fluazifop-butyl, and haloxyfop-methyl and they may be cross-resistant to other Group 1 (Legacy A) 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 Sep 15, 2000 )

Common NamePasto Amargo
SpeciesEriochloa punctata
GroupInhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)
Herbicidesfluazifop-butyl, and haloxyfop-methyl
LocationBolivia, Santa Cruz
Contributors - (Alphabetically)Pablo Franco 
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Pablo Franco
Santa Cruz State; provinces (counties): Obispo Santiesteban, Sara, Guarayos, Ichilo, Chiquitos

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Pablo Franco
The tropical grass, carib grass is frequently found in dry seeded rice, soya bean, maize, and cotton in Santa Cruz State, Bolivia. Dense populations of carib grass are found on most farms in soya bean following widespread and continued use of post-emergence herbicides which inhibit the enzyme ACCase. Farmers have recently reported difficulty in controlling carib grass with recommended doses of fluazifop-p. For fenoxaprop the resistance index was 8.8 times the LD of the biotype San Pedro. The resistance indexes of Monte Cristo were 1.04, 1.25, 1.5, 1.76, 2.5, 2.5, 4.5 for butroxydim, propaquizafop, clodinafop, quizalofop, haloxyfop, cyhalofop, cycloxydim, respectively.

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Pasto Amargo biotype with this Pasto Amargo 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 1 resistant Pasto Amargo 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 1 (Legacy A) resistant Pasto Amargo from Bolivia please update the database.
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BASF Bolivia
Research and Development
Av. San Martin No 1800
of 302
Santa Cruz, de la sierra 237, Santa Cruz
Email Pablo Franco


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Bolivia have been instrumental in providing you this information. Particular thanks is given to Pablo Franco for providing detailed information.
Herbicide Resistant Pasto Amargo Globally
(Eriochloa punctata)
Herbicide Resistant Pasto Amargo Globally
(Eriochloa punctata)
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Herbicide Resistant Pasto Amargo Globally
(Eriochloa punctata)
#CountryFirstYearSituationActive IngredientsSite of Action
1 BoliviaBolivia 1997 Soybean fluazifop-butyl, and haloxyfop-methyl 4 Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
176Eriochloa punctataPasto Amargo555
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