International Survey of Herbicide-Resistant Weeds

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(Sphenoclea zeylanica)

Synthetic Auxins (O/4)

Gooseweed (Sphenoclea zeylanica) is a dicot weed in the Sphenocleaceae family.  In Thailand this weed first evolved resistance to Group O/4 herbicides in 2000 and infests Rice.   Group O/4 herbicides are known as Synthetic Auxins (Synthetic auxins (action like indoleacetic acid)).  Research has shown that these particular biotypes are resistant to 2,4-D and they may be cross-resistant to other Group O/4 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 Jan 16, 2003 )

Common NameGooseweed
SpeciesSphenoclea zeylanica
GroupSynthetic Auxins (O/4)
Contributors - (Alphabetically)Kazuyuki Itoh 
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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Gooseweed biotype with this Gooseweed 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 O/4 resistant Gooseweed 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 O/4 resistant Gooseweed from Thailand please update the database.
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Kobe University
Graduate School of Agricultural Science
1-1 Rokkodaicho
Kobe, 657-0013, Hyogo
Email Kazuyuki Itoh


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Thailand have been instrumental in providing you this information. Particular thanks is given to Kazuyuki Itoh for providing detailed information.
Herbicide Resistant Gooseweed Globally
(Sphenoclea zeylanica)
Herbicide Resistant Gooseweed Globally
(Sphenoclea zeylanica)
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Herbicide Resistant Gooseweed Globally
(Sphenoclea zeylanica)
#CountryFirstYearSituationActive IngredientsSite of Action
1 MalaysiaMalaysia 1995 Rice 2,4-D 28 Synthetic Auxins (O/4)
167Sphenoclea zeylanicaGooseweed131
2 PhilippinesPhilippines 1983 Rice 2,4-D 32 Synthetic Auxins (O/4)
167Sphenoclea zeylanicaGooseweed162
3 ThailandThailand 2000 Rice 2,4-D 47 Synthetic Auxins (O/4)
167Sphenoclea zeylanicaGooseweed5146
Literature about Similar Cases

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