International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Paspalum paniculatum)

EPSP synthase inhibitors (G/9)

Costa Rica, Limón, Alajuela
Arrocillo (Paspalum paniculatum) is a monocot weed in the Poaceae family.  In Costa Rica this weed first evolved resistance to Group G/9 herbicides in 2010 and infests Banana and Plantain, and Pejibaye palm.   Group G/9 herbicides are known as EPSP synthase inhibitors (Inhibition of EPSP synthase).  Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 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.

If we do not have a picture for this weed, or you can provide a better picture (scan, digital camera etc) please please e-mail it to us.

QUIK STATS (last updated Aug 31, 2017 )

Common NameArrocillo
SpeciesPaspalum paniculatum
GroupEPSP synthase inhibitors (G/9)
LocationCosta Rica, Limón, Alajuela
Situation(s)Banana and Plantain, and Pejibaye palm
Contributors - (Alphabetically)Bernal Valverde 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Arrocillo biotype with this Arrocillo 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 Group G/9 resistant Arrocillo 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 G/9 resistant Arrocillo from Costa Rica please update the database.
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Honorary Associate Professor
The University of Copenhagen
Department of Plant and Environmental Sciences
Hojebakkegaard Allé 13
Taastrup, DK-2630, Hovedstaden
Email Bernal Valverde


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 Arrocillo Globally
(Paspalum paniculatum)
Herbicide Resistant Arrocillo Globally
(Paspalum paniculatum)
Drag a column header and drop it here to group by that column
Herbicide Resistant Arrocillo Globally
(Paspalum paniculatum)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Costa RicaCosta Rica 2010 Banana and Plantain, and Pejibaye palm glyphosate 11 EPSP synthase inhibitors (G/9)
335Paspalum paniculatumArrocillo17101
Literature about Similar Cases

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