<b>HRAC Group 4</b> <font size='2'> (Legacy O) </font> resistant Sphenoclea zeylanica from Thailand

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 4 (LEGACY O) RESISTANT GOOSEWEED
(Sphenoclea zeylanica)

Auxin Mimics HRAC Group 4 (Legacy O)

Thailand

INTRODUCTION		GOOSEWEED
Gooseweed (Sphenoclea zeylanica) is a dicot weed in the Sphenocleaceae family. In Thailand this weed first evolved resistance to Group 4 (Legacy O) herbicides in 2000 and infests Rice. Group 4 (Legacy O) herbicides are known as Auxin Mimics (Auxin Mimics ). Research has shown that these particular biotypes are resistant to 2,4-D and they may be cross-resistant to other Group 4 (Legacy O) 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.

QUIK STATS (last updated Jan 16, 2003 )
Common Name	Gooseweed
Species	Sphenoclea zeylanica
Group	Auxin Mimics HRAC Group 4 (Legacy O)
Herbicides	2,4-D
Location	Thailand
Year	2000
Situation(s)	Rice
Contributors - (Alphabetically)	Kazuyuki Itoh
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ACADEMIC ASPECTS

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.

Genetics

Genetic studies on HRAC Group 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 4 (Legacy O) resistant Gooseweed from Thailand please update the database.

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CONTRIBUTING WEED SCIENTISTS

KAZUYUKI ITOH

Professor Kobe University Graduate School of Agricultural Science １-１ Rokkodaicho Kobe, 657-0013, Hyogo Japan Email Kazuyuki Itoh

ACKNOWLEDGEMENTS
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.

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Herbicide Resistant Gooseweed Globally
(Sphenoclea zeylanica)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Malaysia

1995

Rice

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Philippines

1983

Rice

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Thailand

2000

Rice

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Literature about Similar Cases

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Itoh, K.. 1994. Weed ecology and its control in south-east tropical countries. Japanese Journal of Tropical Agriculture 38 : 369 - 373.

For over 20 years, repeated use of the same herbicides has resulted in paraquat resistant biotypes of Crassocephalum crepidioides, Solanum nigrum, Conyza sumatrensis and Amaranthus lividis in plantations, and 2,4-D resistant biotypes of Sphenoclea zeylanica and Fimbristylis miliacea in rice fields in South-East Asia. In irrigated rice areas, rapid changes from transplanting to direct sowing methods have been motivated by the introduction of effective herbicides and combine harvester technology, development of short culm and early maturing rice cultivars, and high labour cost of transplanting. Changes in the rice planting method has caused shifts in weed populations and flora, with large increases being noted for grassy weeds such as the Echinochloa crus-galli complex, Ischaemum rugosum, Leptochloa chinensis and weedy rice. Effective weed control through integrated weed management, involving ecological and biological control, are discussed..

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