International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Atriplex patula)

Photosystem II inhibitors (C1/5)

Halberdleaf Orach (Atriplex patula) is a dicot weed in the Chenopodiaceae family.  In Germany this weed first evolved resistance to Group C1/5 herbicides in 1980 and infests Corn (maize).   Group C1/5 herbicides are known as Photosystem II inhibitors (Inhibition of photosynthesis at photosystem II).  Research has shown that these particular biotypes are resistant to atrazine and they may be cross-resistant to other Group C1/5 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 Sep 15, 2000 )

Common NameHalberdleaf Orach
SpeciesAtriplex patula
GroupPhotosystem II inhibitors (C1/5)
Situation(s)Corn (maize)
Contributors - (Alphabetically) 
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Kees-H (1988). The development of triazine-resistant annual weeds in Bavaria and experience with their control. Die Entwicklung triazinresistenter Samenunkrauter in Bayern und Erfahrungen mit deren Bekampfung. Gesunde-Pflanzen. 1988, 40: 10, 407-412, 414.

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Confirmation Tests

Greenhouse trials comparing a known susceptible Halberdleaf Orach biotype with this Halberdleaf Orach 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 C1/5 resistant Halberdleaf Orach 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

Triazine resistant weeds often exhibit a lower relative fitness when compared to susceptible biotypes.  The most common mutation conferring triazine resistance (Ser 264 to Gly mutation of the psbA gene) also causes a reduction in CO2 fixation, quantum yield, and seed and biomass production.  There is no record in this database referring specifically to fitness studies on Group C1/5 resistant Halberdleaf Orach from Germany.
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The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Germany have been instrumental in providing you this information. 
Herbicide Resistant Halberdleaf Orach Globally
(Atriplex patula)
Herbicide Resistant Halberdleaf Orach Globally
(Atriplex patula)
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Herbicide Resistant Halberdleaf Orach Globally
(Atriplex patula)
#CountryFirstYearSituationActive IngredientsSite of Action
1 BelgiumBelgium 2015 Sugar beets desmedipham, lenacil, metamitron, and phenmedipham 3 Photosystem II inhibitors (C1/5)
26Atriplex patulaHalberdleaf Orach11017
2 GermanyGermany 1980 Corn (maize) atrazine 18 Photosystem II inhibitors (C1/5)
26Atriplex patulaHalberdleaf Orach442
3 United States (Michigan) United StatesMichigan2003 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
26Atriplex patulaHalberdleaf Orach5291
Literature about Similar Cases

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