International Survey of Herbicide-Resistant Weeds

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(Centaurea cyanus)

Auxin Mimics HRAC Group 4 (Legacy O)

Poland, North Eastern Region
Cornflower (Centaurea cyanus) is a dicot weed in the Asteraceae family.  In Poland this weed first evolved resistance to Group 4 (Legacy O) herbicides in 2012 and infests Winter wheat.   Group 4 (Legacy O) herbicides are known as Auxin Mimics (Auxin Mimics ).  Research has shown that these particular biotypes are resistant to dicamba 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.

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QUIK STATS (last updated Dec 09, 2013 )

Common NameCornflower
SpeciesCentaurea cyanus
GroupAuxin Mimics HRAC Group 4 (Legacy O)
LocationPoland, North Eastern Region
Situation(s)Winter wheat
Contributors - (Alphabetically)Kazimierz Adamczewski 
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Kazimierz Adamczewski

General information for Cornflower (Centaurea cyanus) 

In the years 2010-2012 samples from 6 field were collected, the seeds were collected from the field were farmer got poor control of Cornflower. At those field farmers for Cornflower control during many years used herbicides synthetic auxins types.  Susceptible biotype was used as standard Two four replication greenhouse experiments was done.

At first experiment in one dose of three herbicides: dicamba, dichlorprop, and MCPA + MCPP were used.

At second experiment dicamba in 7 deference dose were used, (low and high dose). For each treatment four pot were used as four replication. And 4 weeks after treatment, the plants were cut at the soil surface and their fresh weight was determined. Statistical analysis of date from greenhouse experiments was performed. One biotyp from 6 collected samples was resistant on dicamba. 

One year field trial with dicamba used with 2 doses was determinate.

Mechanism of Resistance. Mechanism of resistance is unknown.

Genetic. The genetic basis of resistance for these biotypes is unknown.

Relative Fitness. There is no done.

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Confirmation Tests

Greenhouse trials comparing a known susceptible Cornflower biotype with this Cornflower 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 4 resistant Cornflower 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 Cornflower from Poland please update the database.
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Institute Of Plant Protection - National Research Institute
Depart. Of Weed Science
Str. Wladyslawa Wegorka 20
Poznań, 60-318, Poznań
Email Kazimierz Adamczewski


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Poland have been instrumental in providing you this information. Particular thanks is given to Kazimierz Adamczewski for providing detailed information.
Herbicide Resistant Cornflower Globally
(Centaurea cyanus)
Herbicide Resistant Cornflower Globally
(Centaurea cyanus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Cornflower Globally
(Centaurea cyanus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 PolandPoland 2010 Winter wheat chlorsulfuron, imazapyr, sulfometuron-methyl, and tribenuron-methyl 33 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
277Centaurea cyanusCornflower5621
2 PolandPoland 2012 Winter wheat dicamba 33 Auxin Mimics ( HRAC Group 4 (Legacy O)
277Centaurea cyanusCornflower6764
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