International Survey of Herbicide-Resistant Weeds

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(Youngia japonica)

PS I Electron Diversion HRAC Group 22 (Legacy D)

China, Sichuan Province
Asiatic Hawksbeard (Youngia japonica) is a dicot weed in the Asteraceae family.  In China this weed first evolved resistance to Group 22 (Legacy D) herbicides in 2009 and infests Unspecified.   Group 22 (Legacy D) herbicides are known as PS I Electron Diversion (PSI Electron Diversion ).  Research has shown that these particular biotypes are resistant to paraquat and they may be cross-resistant to other Group 22 (Legacy D) 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 Jun 10, 2012 )

Common NameAsiatic Hawksbeard
SpeciesYoungia japonica
GroupPS I Electron Diversion HRAC Group 22 (Legacy D)
LocationChina, Sichuan Province
Contributors - (Alphabetically)Xuegang Peng 
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Confirmation Tests

Field trials comparing a known susceptible Asiatic Hawksbeard biotype with this Asiatic Hawksbeard 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 22 resistant Asiatic Hawksbeard 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 22 (Legacy D) resistant Asiatic Hawksbeard from China please update the database.
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Research Associate
Qingdao kingagroot Ltd.
Research institute of maligant weeds
Email Xuegang Peng


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in China have been instrumental in providing you this information. Particular thanks is given to Xuegang Peng for providing detailed information.
Herbicide Resistant Asiatic Hawksbeard Globally
(Youngia japonica)
Herbicide Resistant Asiatic Hawksbeard Globally
(Youngia japonica)
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Herbicide Resistant Asiatic Hawksbeard Globally
(Youngia japonica)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ChinaChina 2009 Unspecified paraquat 9 PS I Electron Diversion (D/22)
175Youngia japonicaAsiatic Hawksbeard5650
2 JapanJapan 1986 Chesnut, Mulberry, and Roadsides diquat, and paraquat 25 PS I Electron Diversion (D/22)
175Youngia japonicaAsiatic Hawksbeard124
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