International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Echinochloa oryzoides)

Very Long-Chain Fatty Acid Synthesis inhibitorsHRAC Group 15 (Legacy K3 N)

United States, California
Early Watergrass (Echinochloa oryzoides) is a monocot weed in the Poaceae family.  In California this weed first evolved resistance to Group 15 (Legacy K3 N) herbicides in 2000 and infests Rice.   Group 15 (Legacy K3 N) herbicides are known as Very Long-Chain Fatty Acid Synthesis inhibitors (Inhibition of Very Long-Chain Fatty Acid Synthesis ).  Research has shown that these particular biotypes are resistant to molinate, and thiobencarb/benthiocarb and they may be cross-resistant to other Group 15 (Legacy K3 N) 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 11, 2010 )

Common NameEarly Watergrass
SpeciesEchinochloa oryzoides
GroupVery Long-Chain Fatty Acid Synthesis inhibitors HRAC Group 15 (Legacy K3 N)
Herbicidesmolinate, and thiobencarb/benthiocarb
LocationUnited States, California
Contributors - (Alphabetically)Albert Fischer 
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Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Early Watergrass biotype with this Early Watergrass 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 15 resistant Early Watergrass 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 15 (Legacy K3 N) resistant Early Watergrass from California please update the database.
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University Of California
Department of Plant Sciences
Weed Ecophysiology
Mail Stop #4 279/279A Robbins Hall
Davis, 95616, California
United States
Email Albert Fischer
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in California have been instrumental in providing you this information. Particular thanks is given to Albert Fischer for providing detailed information.
Herbicide Resistant Early Watergrass Globally
(Echinochloa oryzoides)
Herbicide Resistant Early Watergrass Globally
(Echinochloa oryzoides)
Drag a column header and drop it here to group by that column
Herbicide Resistant Early Watergrass Globally
(Echinochloa oryzoides)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ArgentinaArgentina 2016 Corn (maize), Rice, Roadsides, and Soybean glyphosate 48 Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)
261Echinochloa oryzoidesEarly Watergrass25261
2 TurkeyTurkey 2009 Rice bispyribac-sodium, cyhalofop-butyl, and penoxsulam 71 Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
261Echinochloa oryzoidesEarly Watergrass5530
3 United States (California) United StatesCalifornia2000 Rice molinate, and thiobencarb/benthiocarb 45 Very Long-Chain Fatty Acid Synthesis inhibitors ( HRAC Group 15 (Legacy K3 N)
261Echinochloa oryzoidesEarly Watergrass5492
Literature about Similar Cases

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