(Helianthus annuus)

ALS inhibitors (B/2)

United States, South Dakota
Common Sunflower (Helianthus annuus) is a dicot weed in the Asteraceae family.  In South Dakota this weed first evolved resistance to Group B/2 herbicides in 1996 and infests Cropland.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to imazethapyr 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 Sep 15, 2000 )

Common NameCommon Sunflower
SpeciesHelianthus annuus
GroupALS inhibitors (B/2)
LocationUnited States, South Dakota
Contributors - (Alphabetically)Leon Wrage : retired 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Common Sunflower biotype with this Common Sunflower 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 Common Sunflower 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 B/2 resistant Common Sunflower from South Dakota please update the database.
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Extension Emeritus
South Dakota State University
Plant Science-Box 2140C
Brookings, 57007, South Dakota
United States
Email Leon Wrage : retired
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in South Dakota have been instrumental in providing you this information. Particular thanks is given to Leon Wrage : retired for providing detailed information.
Herbicide Resistant Common Sunflower Globally
(Helianthus annuus)
Herbicide Resistant Common Sunflower Globally
(Helianthus annuus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Common Sunflower Globally
(Helianthus annuus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 FranceFrance 2009 Sunflower imazamox, and tribenuron-methyl 17 ALS inhibitors (B/2)
95Helianthus annuusCommon Sunflower9929
2 United States (Kansas) United StatesKansas1996 Soybean imazethapyr 45 ALS inhibitors (B/2)
95Helianthus annuusCommon Sunflower499
3 United States (Missouri) United StatesMissouri1996 Soybean chlorimuron-ethyl, cloransulam-methyl, flumetsulam, halosulfuron-methyl, imazaquin, imazethapyr, and oxasulfuron 45 ALS inhibitors (B/2)
95Helianthus annuusCommon Sunflower1067
4 United States (South Dakota) United StatesSouth Dakota1996 Cropland imazethapyr 45 ALS inhibitors (B/2)
95Helianthus annuusCommon Sunflower1186
5 United States (Iowa) United StatesIowa1997 Corn (maize), and Soybean chlorimuron-ethyl, and imazethapyr 45 ALS inhibitors (B/2)
95Helianthus annuusCommon Sunflower5230
6 United States (Texas) United StatesTexas2015 Corn (maize) glyphosate 45 EPSP synthase inhibitors (G/9)
95Helianthus annuusCommon Sunflower15062
Literature about Similar Cases

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PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site. Citation:
Heap, I.  The International Herbicide-Resistant Weed Database.  Online.  Monday, April 12, 2021 .  Available Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.