International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Rottboellia cochinchinensis (=R. exaltata))

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Venezuela, Portuguesa
Itchgrass (Rottboellia cochinchinensis (=R. exaltata)) is a monocot weed in the Poaceae family.  In Venezuela this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2004 and infests Corn (maize).   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 foramsulfuron, iodosulfuron-methyl-Na, and nicosulfuron 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.

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 Feb 24, 2015 )

Common NameItchgrass
SpeciesRottboellia cochinchinensis (=R. exaltata)
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesforamsulfuron, iodosulfuron-methyl-Na, and nicosulfuron
LocationVenezuela, Portuguesa
Situation(s)Corn (maize)
Contributors - (Alphabetically)Aida Ortiz 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Itchgrass biotype with this Itchgrass 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 2 resistant Itchgrass 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 Itchgrass from Venezuela please update the database.
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Universidad Central De Venezuela
Avenida Universidad. Campus Maracay
Maracay, 2101, Aragua
Email Aida Ortiz
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Venezuela have been instrumental in providing you this information. Particular thanks is given to Aida Ortiz for providing detailed information.
Herbicide Resistant Itchgrass Globally
(Rottboellia cochinchinensis (=R. exaltata))
Herbicide Resistant Itchgrass Globally
(Rottboellia cochinchinensis (=R. exaltata))
Drag a column header and drop it here to group by that column
Herbicide Resistant Itchgrass Globally
(Rottboellia cochinchinensis (=R. exaltata))
#CountryFirstYearSituationActive IngredientsSite of Action
1 United States (Louisiana) United StatesLouisiana1997 Soybean fluazifop-butyl 45 Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
265Rottboellia cochinchinensis (=R. exaltata)Itchgrass1182
2 VenezuelaVenezuela 2004 Corn (maize) foramsulfuron, iodosulfuron-methyl-Na, and nicosulfuron 80 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
265Rottboellia cochinchinensis (=R. exaltata)Itchgrass5566
Literature about Similar Cases

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