(Centaurea cyanus)

ALS inhibitors (B/2)

Poland, North East region
Cornflower (Centaurea cyanus) is a dicot weed in the Asteraceae family.  In Poland this weed first evolved resistance to Group B/2 herbicides in 2010 and infests Winter wheat.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to chlorsulfuron, imazapyr, sulfometuron-methyl, and tribenuron-methyl and they may be cross-resistant to other Group B/2 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 Mar 31, 2015 )

Common NameCornflower
SpeciesCentaurea cyanus
GroupALS inhibitors (B/2)
Herbicideschlorsulfuron, imazapyr, sulfometuron-methyl, and tribenuron-methyl
LocationPoland, North East region
Situation(s)Winter wheat
Contributors - (Alphabetically)Kazimierz Adamczewski, and Roman Kierzek 
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Kazimierz Adamczewski
Adamczewski K., R. Kierzek. 2010. Chaber blawatek (Centaurea cyanus L.) odpornej na inhibitory ALS (herbicydy sulfonylomocznikowe). (Cornflower (Centaurea cyanus L) cross resistance on ALS inhibitors). Prog. Plant Protection/Post. Ochr. Roslin 50/1: 287-290. (in Polish, summery in English).

Adamczewski K., Kierzek R. 2011. Mechanizm odpornosci chabra blawatka (Centurea cyanus L) na herbicydy sulfonylomocznikowe. (Mechanism of resistance on acetylolactate synyhase (ALS of Centaurea cyanus L. biotypes cross-resistant) Prog. Plant Protection/Post. Ochr. Roslin 51/1: 317–324. (in Polish, summery in English).

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Kazimierz Adamczewski
In the years 2007-2010 28 samples of seeds were collected from the field were farmer got problem with control Cornflower. Susceptible biotype was used as standard Two four replication greenhouse experiments was done.
At first experiment in one dose of two herbicides: tribenuron methyl and chlorsulfuron. And on selected 5 biotypes secend type experiment was done.
At secend experiment tribenuron methyl, sulfometuron and imazapyr each 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.
In two sites one year field trials with tribenuron methyl and chlorsulfuron used with 4 dose were also determined

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Kazimierz Adamczewski
Mechanism of resistance for three biotypes is target site resistant Pro-197 and two of those got also Tri-574, and for two (populations) is unknown. ((Each biotype become from difference field and distance between the fields are about 5 to 20 km)

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Confirmation Tests

Field, Greenhouse, and Laboratory 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 Group B/2 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

Studies on the mechanism of resistance of Group B/2 resistant Cornflower from Poland indicate that resistance is due to an altered target site.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
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 B/2 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
Research Scientist
National Research Institute
Institute of Plant Protection - Weed Science Department
Wladyslawa Wegorka 20
Poznan, 60-318, Poznań
Email Roman Kierzek


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, and Roman Kierzek 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 ALS inhibitors (B/2)
277Centaurea cyanusCornflower5621
2 PolandPoland 2012 Winter wheat dicamba 33 Auxin Mimics (O/4)
277Centaurea cyanusCornflower6764
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