International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
HRAC GROUP 2 (LEGACY B) RESISTANT PASTO HONDURAS (MEXICANGRASS)
(Ixophorus unisetus)


Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Costa Rica, Guanacaste
INTRODUCTION PASTO HONDURAS (MEXICANGRASS)
Pasto Honduras (Mexicangrass) (Ixophorus unisetus) is a monocot weed in the Poaceae family.  In Costa Rica this weed first evolved resistance to Group 2 (Legacy B) herbicides in 1988 and infests Roadsides.   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 imazapyr 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 Sep 15, 2000 )

Common NamePasto Honduras (Mexicangrass)
SpeciesIxophorus unisetus
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesimazapyr
LocationCosta Rica, Guanacaste
Year1988
Situation(s)Roadsides
Contributors - (Alphabetically)Bernal Valverde 
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Bernal Valverde
Northern Pacific area of Costa Rica only. Puntorenas and Guanacaste provinces.

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GENERAL

Bernal Valverde
Proc. Brighton Crop Prot. Conference on Weeds. 1993. 8C-10. p. 1189-1194.

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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Pasto Honduras (Mexicangrass) biotype with this Pasto Honduras (Mexicangrass) 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 Pasto Honduras (Mexicangrass) 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 Pasto Honduras (Mexicangrass) from Costa Rica please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

BERNAL VALVERDE
Honorary Associate Professor
The University of Copenhagen
Department of Plant and Environmental Sciences
Hojebakkegaard Allé 13
Taastrup, DK-2630, Hovedstaden
Denmark
Email Bernal Valverde

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Costa Rica have been instrumental in providing you this information. Particular thanks is given to Bernal Valverde for providing detailed information.
Herbicide Resistant Pasto Honduras (Mexicangrass) Globally
(Ixophorus unisetus)
Herbicide Resistant Pasto Honduras (Mexicangrass) Globally
(Ixophorus unisetus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Pasto Honduras (Mexicangrass) Globally
(Ixophorus unisetus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Costa RicaCosta Rica 1988 Roadsides imazapyr 11 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
100Ixophorus unisetusPasto Honduras (Mexicangrass)74
2 MexicoMexico 2014 Corn (maize) nicosulfuron 29 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
100Ixophorus unisetusPasto Honduras (Mexicangrass)9925
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