International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP B/2 RESISTANT GIANT RAGWEED
(Ambrosia trifida)


ALS inhibitors (B/2)

United States, Iowa
INTRODUCTION GIANT RAGWEED
Giant Ragweed (Ambrosia trifida) is a dicot weed in the Asteraceae family.  In Iowa this weed first evolved resistance to Group B/2 herbicides in 2000 and infests Corn (maize), and Soybean.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)).  Research has shown that these particular biotypes are resistant to cloransulam-methyl, primisulfuron-methyl, and prosulfuron 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 Jan 15, 2010 )

Common NameGiant Ragweed
SpeciesAmbrosia trifida
GroupALS inhibitors (B/2)
Herbicidescloransulam-methyl, primisulfuron-methyl, and prosulfuron
LocationUnited States, Iowa
Year2000
Situation(s)Corn (maize), and Soybean
Contributors - (Alphabetically)Robert Hartzler, and Ian Zelaya 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Ian Zelaya
The resistant giant ragweed biotype was collected at Werner Farm in Scott County, IA. Greenhouse and laboratory studies confirmed that the Werner Farm biotype was cross-resistant to cloransulam-methyl (GR50 R:S ratio = 21) and primisulfuron-methyl + prosulfuron (GR50 R:S ratio = 28). The susceptible giant ragweed biotype was collected in Zearing, IA. Source: Zelaya, I. A., and M. D. K. Owen. 2004. Evolved resistance to acetolactate synthase-inhibiting herbicides in common sunflower (Helianthus annuus), giant ragweed (Ambrosia trifida), and shattercane (Sorghum bicolor) in Iowa. Weed Science 52:538-548.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Giant Ragweed biotype with this Giant Ragweed biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.
 
Genetics

Genetic studies on Group B/2 resistant Giant Ragweed 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 Giant Ragweed from Iowa 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 Giant Ragweed from Iowa please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

ROBERT HARTZLER
Extension Weed Specialist and Professor of Agronomy
Iowa State University
Weed Science
2104 Agronomy Hall
Ames, 50011, Iowa
United States
Email Robert Hartzler
Web   : Web Site Link
IAN ZELAYA
Extension Weed Specialist and Professor of Agronomy
Syngenta
Weed Control Unit
Carrera 7 No. 113-43
Piso 10
Bogotá, 50011, Iowa
Colombia
Email Ian Zelaya
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Iowa have been instrumental in providing you this information. Particular thanks is given to Robert Hartzler, and Ian Zelaya for providing detailed information.
Herbicide Resistant Giant Ragweed Globally
(Ambrosia trifida)
Herbicide Resistant Giant Ragweed Globally
(Ambrosia trifida)
Drag a column header and drop it here to group by that column
Herbicide Resistant Giant Ragweed Globally
(Ambrosia trifida)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Ontario) CanadaOntario2008 Soybean glyphosate 7 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5483
2 Canada (Ontario) CanadaOntario2011 Soybean cloransulam-methyl, and glyphosate 7 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed7833
3 United States (Indiana) United StatesIndiana1998 Soybean cloransulam-methyl, and imazethapyr 45 ALS inhibitors (B/2)
184Ambrosia trifidaGiant Ragweed1123
4 United States (Illinois) United StatesIllinois1998 Soybean cloransulam-methyl, and imazethapyr 45 ALS inhibitors (B/2)
184Ambrosia trifidaGiant Ragweed1124
5 United States (Ohio) United StatesOhio1998 Soybean chlorimuron-ethyl, cloransulam-methyl, imazamox, imazaquin, primisulfuron-methyl, and prosulfuron 45 ALS inhibitors (B/2)
184Ambrosia trifidaGiant Ragweed1164
6 United States (Iowa) United StatesIowa2000 Corn (maize), and Soybean cloransulam-methyl, primisulfuron-methyl, and prosulfuron 45 ALS inhibitors (B/2)
184Ambrosia trifidaGiant Ragweed5231
7 United States (Ohio) United StatesOhio2004 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5278
8 United States (Indiana) United StatesIndiana2005 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5279
9 United States (Arkansas) United StatesArkansas2005 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5345
10 United States (Kentucky) United StatesKentucky2005 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed7878
11 United States (Kansas) United StatesKansas2006 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5304
12 United States (Minnesota) United StatesMinnesota2006 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5333
13 United States (Ohio) United StatesOhio2006 Soybean chlorimuron-ethyl, cloransulam-methyl, and glyphosate 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5408
14 United States (Tennessee) United StatesTennessee2007 Cotton, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5335
15 United States (Minnesota) United StatesMinnesota2008 Soybean cloransulam-methyl, and glyphosate 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5508
16 United States (Iowa) United StatesIowa2009 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5463
17 United States (Missouri) United StatesMissouri2009 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5466
18 United States (Mississippi) United StatesMississippi2010 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5504
19 United States (Nebraska) United StatesNebraska2010 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5573
20 United States (Wisconsin) United StatesWisconsin2011 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed5660
21 United States (Missouri) United StatesMissouri2011 Corn (maize) chlorimuron-ethyl, cloransulam-methyl, and glyphosate 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
184Ambrosia trifidaGiant Ragweed7808
22 United States (Wisconsin) United StatesWisconsin2013 Soybean cloransulam-methyl, and imazamox 45 ALS inhibitors (B/2)
184Ambrosia trifidaGiant Ragweed7822
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